On Mon, 13 Nov 2017 08:59:01 -0800 (PST), whisky-dave
wrote:

On Monday, 13 November 2017 16:24:56 UTC, John Rumm wrote:
On 13/11/2017 13:58, whisky-dave wrote:

All we need is a heating engineer that knows stuff, both theory and in practice
It was 12C @ 9am, now 16C @ 13:45.

This is with 5 of 2KW heaters and 2 of 1.5KW heaters.

So if yuo wanted the demp to be 16C before the 10am class how many heaters would we need in total. ?


It seems like working out the heat loss from first principles would be a
good start:

http://wiki.diyfaq.org.uk/index.php/Heat_loss

Once you have a feel for that, you know what power input you will need
to maintain a steady state at a desired temperature. You would then need
to size the heating to be able to exceed that by enough to lift it to a
working temperature in a reasonable time frame (and what that is will
depend a bit on how the place s built - you may be able to achieve it in
a few hours, or you might need to heat it continuously if it turns out
the answer is "days").

So how would yuo go about that ?

Do the sums?

http://wiki.diyfaq.org.uk/index.php/...Worked_Example

What are the things you need to know ?

http://wiki.diyfaq.org.uk/index.php/...Worked_Example

Think about it and you'll realise the where the biggest error would be.

Erm yes ...

So, you either try stuff (different types / sizes of heater) or buy
some hats, gloves and coats. ;-)

Cheers, T i m

On Mon, 13 Nov 2017 09:04:54 -0800 (PST), whisky-dave
wrote:

snip

although the department did
have one of those autotransformers installed a few years ago they are
meant to save money by reducing the voltage slightly I think.

That will make matters worse in this circumstance.

yes I know so why were we conned into having one.

Because the people making the decisions didn't know enough about basic
science?


(also not going to help reduce costs either since the heaters will just
need to run longer to provide the required energy transfer).

Yep we all know this but those in charge obviously didnt they just saw saving on electric and no doubt anyone saving money will get promoted.

See above. I have 25l of top quality 'Snake oil' here they can buy off
me if they want? ;-)


Cheers, T i m

T i m wrote:

On Mon, 13 Nov 2017 08:19:36 -0800 (PST), whisky-dave
wrote:

snip



Nothing of which help work out how many we need.

That wasn't what I was talking about and couldn't without you telling
us more about the entire scenario (including the thermal values for
the rooms / building etc). I gave you most of the tools, costs and
options within my first few posts and I couldn't do much more without
more information (you know, like knowing the likelihood of us leaving
the EU to be likely to be a 'good thing' or not before deciding to do
it). ;-)

Perhaps that's why we have 14 due to arrive this week.

It might just be a few more to send back. ;-(

Maybe they could get a 2-3kw garage / workshop fan heater in to try?

https://www.machinemart.co.uk/c/electric-heaters/
https://www.machinemart.co.uk/p/hone...tility-heater/

Cheers, T i m

The OP said somewhere in the thread that the lab was supplied by an
autotransformer. (This is of course a completely stupid idea. The
electronic equipment will simply use its usual power, perhaps slightly
less efficiently. And heaters will produce slightly less heat, so that
a thermostat either in the heater or the room will leave them on longer.
So it can never save money. And because it is less than 100% efficient
it will always lose money.) This is clearly becoming overloaded with
five 700W heaters, so will never provide significantly more electrical
heating however many radiators they buy.


Step one is to either put in a new supply with several suitable ring or
radial circuits bypassing the autotransformer or remove the latter. It
may have some scrap value.


--

Roger Hayter

John Rumm wrote:

On 13/11/2017 13:10, whisky-dave wrote:
On Saturday, 11 November 2017 15:10:34 UTC, ARW wrote:

Voltage 202


The fact that the voltage drops to 202V suggests that the wiring is
a little bit suspect.

How ? Surely it's just basic ohms law,

It is... and one should design circuits such that at full load they
still meet the basic requirement of showing no more than 4% or 5%[1]
voltage drop.

Since it does not appear that yours are meeting that requirement, it
would suggest that either the cable run in the circuit itself or that of
the sub main feeding the CU at the origin of the circuit is
underspecified for the length of cable in use.

[1] Used to be 4% on all circuits. These days its 5% on power circuits,
but 3% on lighting circuits.


although the department did
have one of those autotransformers installed a few years ago they are
meant to save money by reducing the voltage slightly I think.

That will make matters worse in this circumstance.

(also not going to help reduce costs either since the heaters will just
need to run longer to provide the required energy transfer).

I thought even on extention leads that the voltage drop increased us
the current went up pretty basic stuff I thought.

Indeed it is.

It seems he already has as much electrical heating as that
autotransformer will ever supply, and is probably exceeding its ratings.
Perhaps someone who knows where it is could have a quick look and see if
any smoke comes out when the voltage drops to 202V?

--

Roger Hayter

On 13/11/17 20:38, Roger Hayter wrote:
It seems he already has as much electrical heating as that
autotransformer will ever supply, and is probably exceeding its ratings.
Perhaps someone who knows where it is could have a quick look and see if
any smoke comes out when the voltage drops to 202V?


well at least the transformer is contributing to the heating...

On Mon, 13 Nov 2017 20:38:37 +0000, (Roger Hayter)
wrote:
snip

Maybe they could get a 2-3kw garage / workshop fan heater in to try?

https://www.machinemart.co.uk/c/electric-heaters/
https://www.machinemart.co.uk/p/hone...tility-heater/


The OP said somewhere in the thread that the lab was supplied by an
autotransformer. (This is of course a completely stupid idea. The
electronic equipment will simply use its usual power, perhaps slightly
less efficiently. And heaters will produce slightly less heat, so that
a thermostat either in the heater or the room will leave them on longer.
So it can never save money. And because it is less than 100% efficient
it will always lose money.)

Noted previously and agreed.

This is clearly becoming overloaded with
five 700W heaters,

I think it was more when they were on 2kw but actually
(intermittently) drawing 1.6kW or somesuch.

so will never provide significantly more electrical
heating however many radiators they buy.

Quite ... and why I suggested they try something else.

A 'problem' with all radiators, especially small ones (for the space)
is you don't actually feel the effect until they have warmed the
entire space, especially if you have high ceilings and no real airflow
around the space (and why tall buildings / rooms sometimes have fans
in tubes blowing the heat back down to the lower levels). So, for the
same volume of room and the same wattage of heater, a fan heater might
be 'noticed / felt' by the inhabitants more / sooner than that from a
straight convection heater. If the situation is worse, many don't try
to heat the space at all but heat the people, often using radiant
heaters (I can often feel the IR heaters in the ceilings of DIY sheds
and the like because I'm folically challenged). ;-)


Step one is to either put in a new supply with several suitable ring or
radial circuits bypassing the autotransformer or remove the latter.

If they bought an autotransformer I'm not sure anyone is going to hold
their hand up and pay again to have it taken out. ;-(

It
may have some scrap value.

Hehe ... only any real value if it's actually filled with copper.
However, if they bought the autotxfmr in the first place they may have
bought the 'aluminium cored one because it was better as it was
lighter. ;-(

We still don't know what sort of building we are talking about and if
other 'improvements' could be made to conserve the heat they do have?
Like, if there is a draughty doorway I wonder if you could fit
something like a forklift curtain, or another set of doors to form an
airlock, especially on any doors going directly to the outside?

What about workmats on the floor, especially if it's a solid floor
etc?

Or a hot air curtain on the external doors to stop the cold air coming
in (and the warm air going out)?

https://en.wikipedia.org/wiki/Air_door

Cheers, T i m

On 13/11/2017 16:59, whisky-dave wrote:
On Monday, 13 November 2017 16:24:56 UTC, John Rumm wrote:
On 13/11/2017 13:58, whisky-dave wrote:

All we need is a heating engineer that knows stuff, both theory and in practice
It was 12C @ 9am, now 16C @ 13:45.

This is with 5 of 2KW heaters and 2 of 1.5KW heaters.

So if yuo wanted the demp to be 16C before the 10am class how many heaters would we need in total. ?


It seems like working out the heat loss from first principles would be a
good start:

http://wiki.diyfaq.org.uk/index.php/Heat_loss

Once you have a feel for that, you know what power input you will need
to maintain a steady state at a desired temperature. You would then need
to size the heating to be able to exceed that by enough to lift it to a
working temperature in a reasonable time frame (and what that is will
depend a bit on how the place s built - you may be able to achieve it in
a few hours, or you might need to heat it continuously if it turns out
the answer is "days").

So how would yuo go about that ?

A combination of experience with the current heating system, and some
knowledge of the construction of the building (i.e. how much thermal
mass it has, and where that mass is with respect to the insulation (if
it has any).

For buildings that are reasonably will insulated, and have their thermal
mass outside of the insulation, then conventional thermostatic
controlled stats will work ok. For more "difficult" buildings then
optimising stats that learn the response of the building and adjust the
on times automatically can work well. Some places however which have
large volumes of masonry and no insulation will frequently take days of
continuous heating to get to a sensible temperature. In those cases just
setting the heating output based on an external stat (i.e. a weather
compensating type of arrangement) is often the easiest way so that you
track the general trend in the external temperature to aim at a roughly
constant inside temp).

What are the things you need to know ?

For what, heat loss calcs? General details of the construction, and the
areas involved.

If it turns out you need 5kW to keep pace with losses on a cold day,
then you know that if you have 7kW available, you should be able to
reach the target temperature eventually. Then it becomes a question of
optimising start times and working out what your minimum setback
temperature is. If it turns out you can only gain 1 deg/hour, then you
probably want your setback temp no lower than 15 degrees, and the
heating to go to full power at say 7am to get a comfortable temp by 10am.

Think about it and you'll realise the where the biggest error would be.

Will I?

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 13/11/2017 20:38, Roger Hayter wrote:

It seems he already has as much electrical heating as that
autotransformer will ever supply, and is probably exceeding its ratings.
Perhaps someone who knows where it is could have a quick look and see if
any smoke comes out when the voltage drops to 202V?

ISTR that bigclive did a tear-down on one of those voltage reduction
units. At some load point it actually had relays to bridge itself out of
the supply as a self protection mechanism. So you may find enough load
actually takes it out of circuit.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 13/11/2017 17:04, whisky-dave wrote:
On Monday, 13 November 2017 16:37:27 UTC, John Rumm wrote:
On 13/11/2017 13:10, whisky-dave wrote:
On Saturday, 11 November 2017 15:10:34 UTC, ARW wrote:

Voltage 202


The fact that the voltage drops to 202V suggests that the wiring is
a little bit suspect.

How ? Surely it's just basic ohms law,

It is... and one should design circuits such that at full load they
still meet the basic requirement of showing no more than 4% or 5%[1]
voltage drop.

So what should be the full load on a 32 amp MCB ?

The maximum design load would be 32A. With that load, you should drop no
more than 5% for socket circuits. If you overload the circuit, then its
not unreasonable to be out of spec for voltage drop.

Since it does not appear that yours are meeting that requirement,

how do you work that out ?

You said the voltage was 202V. If your starting point was 220V then that
is well out of spec (given your actual applied load would probably be
close to the 32A design load even with 5 heaters running, since the
actual power dissipated by each heater at that voltage would be well
under the nominal 2kW)

it
would suggest that either the cable run in the circuit itself or that of
the sub main feeding the CU at the origin of the circuit is
underspecified for the length of cable in use.

This isn't a home CU unit.

Doesn't matter...



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Rumm wrote:

On 13/11/2017 20:38, Roger Hayter wrote:

It seems he already has as much electrical heating as that
autotransformer will ever supply, and is probably exceeding its ratings.
Perhaps someone who knows where it is could have a quick look and see if
any smoke comes out when the voltage drops to 202V?

ISTR that bigclive did a tear-down on one of those voltage reduction
units. At some load point it actually had relays to bridge itself out of
the supply as a self protection mechanism. So you may find enough load
actually takes it out of circuit.

That sounds a sensible arrangement, But doesn't the marked voltage
drop make it a bit unlikely?

--

Roger Hayter

On Monday, 13 November 2017 17:21:04 UTC, T i m wrote:
On Mon, 13 Nov 2017 08:19:36 -0800 (PST), whisky-dave
wrote:

snip

It seems to trip out at about 98C (halfway up the last fin)
so drops to 700W at that point.

Right, it sounds to me like there is a 100 DegC upper limit stat and
only the heavy heater element is going though it.

So it's not realy a cut-out more like a cut-back.

Well, same thing in this case.

No it's not.



So what does a cut-out do.

What it says. It's a thermal switch that cuts out (in this case) when
the temperature reaches a certain point and cuts back in again when
the temperature has dropped back to a certain (lower) point again
(just like a thermostat). You can get them that are wired in reverse
to control cooling fans etc.

So is it a cut-out or a thermostat, you seem to be saying tehy are the same..


snip

Seems to drop to about 76C then then the full power comes on 1725W.

Yup, sounds about the right hysteresis range for a thermal limit
switch.

So is that the new name for a cut-out.

Not new (other than to you possibly and in this specific message),
just 'another'.

So you can't tell the differnce between those labels is that it. ?
Thermostat, cut-out, resettable fuse.



I believe on 2000W and the main (room-ish) stat on max, the rad is
unable to dissipate enough heat to stop it 'overheating' and therefore
it's modulating the power on the 'overtemp stat'.

Seems likes what's happening, but if I were designing a cut-out to stop over heating I'd get the whole thing to switch off to 0W as a safety feature.

Quite.

But of course it's not called a cut out but Overheat protection.

Yes, where the 'overheat protection' is provided by an overtemp /
thermal / cut-out / switch *and / plus* a one way (non-resettable),
thermal fuse.

As I thought you can;t tell teh difernce between these terms a thermostat is the same as a cut-out.


So many options to consider one wonders how yuo;d calculate how many heaters would be needed,

Not really ... once you have taken the measurements you just need to
do the sums.

What measurements, most situations you decide what you want before taking measurements, because yuo buy based on teh specifications of the product.



What you can measure (and it seems like you have been
able to do that bit) you can manage. ;-)

Yep, far better than those using theory.


it;s a problem we're having at this very moment and discussing , how many more to buy and who should pay for them.


You would have to decide that based on other factors that you haven't
yet covered (less I missed or forgot), like the need / usage,
environment (building type, thermal characteristics etc).

Yes and those were prettyy much fixed when it was built, so how would an engineer predict what sort of heater and what power would be required ?



Like, my mate used a waste oil burning space hearer (blown air) in his
garage but it got old and I think they banned them (or were going to
if not heavily updated etc). He got the gas board in and (long short),
much to my mates questioning, they fitted two blown air gas heaters
that were never going to be up to the job. The sales rep suggested he
set the timer to come on at say 6am so the place would be warm for
8am, completely ignoring that the first thing my mate typically did
was open up the end of the garage to move cars in and out (and in so
doing losing any heat). So, they eventually ripped out the new units
and fitted bigger ones that were up to the job.

Suppose he was told that 10KW heater would be required to do what he wanted and then on installign them, he found that after a while the 5x2KW were no longer 2KW but reduced in power to 700W, would that change any calculation, I'msuggesting if that is the case he'd need 13-14 of thse heaters wouldn't he.


So, to 'feel the affect' of the heating effect you might be better of
with industrial fan / space heaters or IR heaters etc.

Neither of which are allowed in the teaching lab due to H&S.



When you say 'apart' you just mean the plastic end cover off. ;-)

What plastic end cover ?

Normally the controls / wiring are in a plastic cover of some sort (so
you don't burn yourself when touching it and it's cheaper to make
etc).

thought the plastic would be likely to melt

Never seen a plastic handle on a hot air gun or soldering iron?

Yes but it's insulated from the heat part.


and if I did it would then fail regualtaions as we;d need it PAT tested before it was put back into use.

See above. Not all 'plastics' are created equal mate. ;-)

and I doubt the best plastics are in use in his cheap heater.

But in the manual they do list things like the carry handle adn everything else the seem to have missed out the section on how to get to the wiring.
Perhaps it;s not user accesable like changing the oil.



So another reason njot to take it apart, I'd prefer that we were supplied with working equipment that was up for the job.

But 'a reason' to take it apart would possibly to prove that it wasn't
wired correctly?

I don;t care. I have 5 of them and of the 3 I tested they all do the same.




It may be that this entire batch of heaters
have been designed badly or wired incorrectly ... or that there is a
second upper-limit stat (or more likely a thermal fuse) that would
ultimately protect the rad from a real overtemp situation (like if you
covered it in towels, even when only on the 700W element).


Nothing of which help work out how many we need.

That wasn't what I was talking about and couldn't without you telling
us more about the entire scenario

you don't need to know more that is the point.
It's pretty basic maths and even simplier if you think before calculating.






(including the thermal values for
the rooms / building etc). I gave you most of the tools, costs and
options within my first few posts and I couldn't do much more without
more information (you know, like knowing the likelihood of us leaving
the EU to be likely to be a 'good thing' or not before deciding to do
it). ;-)

No wonder you can't work it out.



Perhaps that's why we have 14 due to arrive this week.

It might just be a few more to send back. ;-(

They seem to be working as indicated why would I send them back ?


Maybe they could get a 2-3kw garage / workshop fan heater in to try?

Not allowed in a teaching lab .

would be handy as my brother works for clarke and he'd get a 10% discount IIRC.

But how do you know what power they are ? in order for your calculations to work.



https://www.machinemart.co.uk/c/electric-heaters/
https://www.machinemart.co.uk/p/hone...tility-heater/

Cheers, T i m

On Monday, 13 November 2017 17:24:50 UTC, T i m wrote:
On Mon, 13 Nov 2017 08:59:01 -0800 (PST), whisky-dave
wrote:

On Monday, 13 November 2017 16:24:56 UTC, John Rumm wrote:
On 13/11/2017 13:58, whisky-dave wrote:

All we need is a heating engineer that knows stuff, both theory and in practice
It was 12C @ 9am, now 16C @ 13:45.

This is with 5 of 2KW heaters and 2 of 1.5KW heaters.

So if yuo wanted the demp to be 16C before the 10am class how many heaters would we need in total. ?


It seems like working out the heat loss from first principles would be a
good start:

http://wiki.diyfaq.org.uk/index.php/Heat_loss

Once you have a feel for that, you know what power input you will need
to maintain a steady state at a desired temperature. You would then need
to size the heating to be able to exceed that by enough to lift it to a
working temperature in a reasonable time frame (and what that is will
depend a bit on how the place s built - you may be able to achieve it in
a few hours, or you might need to heat it continuously if it turns out
the answer is "days").

So how would yuo go about that ?

Do the sums?

http://wiki.diyfaq.org.uk/index.php/...Worked_Example

What are the things you need to know ?

http://wiki.diyfaq.org.uk/index.php/...Worked_Example

Think about it and you'll realise the where the biggest error would be.

Erm yes ...

So where ?




So, you either try stuff (different types / sizes of heater) or buy
some hats, gloves and coats. ;-)

for 420 students yeah great idea.


Cheers, T i m

On Monday, 13 November 2017 17:29:02 UTC, T i m wrote:
On Mon, 13 Nov 2017 09:04:54 -0800 (PST), whisky-dave
wrote:

snip

although the department did
have one of those autotransformers installed a few years ago they are
meant to save money by reducing the voltage slightly I think.

That will make matters worse in this circumstance.

yes I know so why were we conned into having one.

Because the people making the decisions didn't know enough about basic
science?

or their priorities were keeping the costs down or saving money or getting promoted, or that once the lectures offices got enough heat, just extent the heating system further and any heat left would end up in the teaching labs, which I think is basically what happened. Tbe teachingmlabs werenlt consideredd important in 1955 or there abouts.

Here;s one of the first pictures I've seen of the lab not sure of the year, so if anyone has any ideas... I think late 50s early 60s rather than 40s
This area is now two offices, previosuly it was about 15-20% of the student lab.

https://www.dropbox.com/s/35ntzcnna5...1940s.jpg?dl=0




(also not going to help reduce costs either since the heaters will just
need to run longer to provide the required energy transfer).

Yep we all know this but those in charge obviously didnt they just saw saving on electric and no doubt anyone saving money will get promoted.

See above. I have 25l of top quality 'Snake oil' here they can buy off
me if they want? ;-)

Nah that's OK I know how important snake oil is, and we haven't got any squeeky snakes to oil, obviously your snakes squeek more than ours it seems ;-P

25L thought it was 251 which is actually the number of the teaching lab, well 251, 253 & 255 are the teaching labs in this area

"whisky-dave" wrote in message
...
On Monday, 13 November 2017 17:29:02 UTC, T i m wrote:
On Mon, 13 Nov 2017 09:04:54 -0800 (PST), whisky-dave
wrote:

snip

although the department did
have one of those autotransformers installed a few years ago they
are
meant to save money by reducing the voltage slightly I think.

That will make matters worse in this circumstance.

yes I know so why were we conned into having one.

Because the people making the decisions didn't know enough about basic
science?

or their priorities were keeping the costs down or saving money or
getting promoted, or that once the lectures offices got enough heat, just
extent the heating system further and any heat left would end up in the
teaching labs, which I think is basically what happened. Tbe teachingmlabs
werenlt consideredd important in 1955 or there abouts.

They were here. Like I said, you fools ****ed everything and still do.

Here;s one of the first pictures I've seen of the lab not sure of the
year, so if anyone has any ideas... I think late 50s early 60s rather
than 40s
This area is now two offices, previosuly it was about 15-20% of the
student lab.

https://www.dropbox.com/s/35ntzcnna5...1940s.jpg?dl=0




(also not going to help reduce costs either since the heaters will
just
need to run longer to provide the required energy transfer).

Yep we all know this but those in charge obviously didnt they just saw
saving on electric and no doubt anyone saving money will get promoted.

See above. I have 25l of top quality 'Snake oil' here they can buy off
me if they want? ;-)

Nah that's OK I know how important snake oil is, and we haven't got any
squeeky snakes to oil, obviously your snakes squeek more than ours it
seems ;-P

25L thought it was 251 which is actually the number of the teaching lab,
well 251, 253 & 255 are the teaching labs in this area

On Tue, 14 Nov 2017 05:29:29 -0800 (PST), whisky-dave
wrote:

On Monday, 13 November 2017 17:21:04 UTC, T i m wrote:
On Mon, 13 Nov 2017 08:19:36 -0800 (PST), whisky-dave
wrote:

snip

It seems to trip out at about 98C (halfway up the last fin)
so drops to 700W at that point.

Right, it sounds to me like there is a 100 DegC upper limit stat and
only the heavy heater element is going though it.

So it's not realy a cut-out more like a cut-back.

Well, same thing in this case.

No it's not.

Aren't you the one who seemed to have no idea about any of this?

I am describing the electrical device as being what it is, whilst you
are trying to conflate that and the function you (you believe) you see
it having.


So what does a cut-out do.

What it says. It's a thermal switch that cuts out (in this case) when
the temperature reaches a certain point and cuts back in again when
the temperature has dropped back to a certain (lower) point again
(just like a thermostat). You can get them that are wired in reverse
to control cooling fans etc.

So is it a cut-out or a thermostat, you seem to be saying tehy are the same.

Electrically, in this case the result of either 'activating' are the
exact same thing, eg, cutting off the flow of electricity through the
element(s).


snip

Seems to drop to about 76C then then the full power comes on 1725W.

Yup, sounds about the right hysteresis range for a thermal limit
switch.

So is that the new name for a cut-out.

Not new (other than to you possibly and in this specific message),
just 'another'.

So you can't tell the differnce between those labels is that it. ?
Thermostat, cut-out, resettable fuse.

What? As you don't want to open a unit up and without recourse to a
wiring diagram you would (normally) have no idea which one had
operated if the unit had gone off (as they are all usually in series).
ITRW, if you adjust the main thermostat and it all comes back on, of
leave it to cool down a bit and it comes back on, then the thermal
fuse hasn't blown.



I believe on 2000W and the main (room-ish) stat on max, the rad is
unable to dissipate enough heat to stop it 'overheating' and therefore
it's modulating the power on the 'overtemp stat'.

Seems likes what's happening, but if I were designing a cut-out to stop over heating I'd get the whole thing to switch off to 0W as a safety feature.

Quite.

But of course it's not called a cut out but Overheat protection.

Yes, where the 'overheat protection' is provided by an overtemp /
thermal / cut-out / switch *and / plus* a one way (non-resettable),
thermal fuse.

As I thought you can;t tell teh difernce between these terms a thermostat is the same as a cut-out.

Are you now just trolling mate?


So many options to consider one wonders how yuo;d calculate how many heaters would be needed,

Not really ... once you have taken the measurements you just need to
do the sums.

What measurements, most situations you decide what you want before taking measurements, because yuo buy based on teh specifications of the product.

Not in this case you shouldn't (tail wagging the dog) and John has
explained the process clearly enough elsewhere.



What you can measure (and it seems like you have been
able to do that bit) you can manage. ;-)

Yep, far better than those using theory.

But only as an 'observation'. You may now have a large quantity of
useless heaters on your hands.

You bought a car to tow a trailer but with no idea how big the trailer
was.


it;s a problem we're having at this very moment and discussing , how many more to buy and who should pay for them.


You would have to decide that based on other factors that you haven't
yet covered (less I missed or forgot), like the need / usage,
environment (building type, thermal characteristics etc).

Yes and those were prettyy much fixed when it was built,

Indeed?

so how would an engineer predict what sort of heater and what power would be required ?

See Johns replies for an answer on those.


Like, my mate used a waste oil burning space hearer (blown air) in his
garage but it got old and I think they banned them (or were going to
if not heavily updated etc). He got the gas board in and (long short),
much to my mates questioning, they fitted two blown air gas heaters
that were never going to be up to the job. The sales rep suggested he
set the timer to come on at say 6am so the place would be warm for
8am, completely ignoring that the first thing my mate typically did
was open up the end of the garage to move cars in and out (and in so
doing losing any heat). So, they eventually ripped out the new units
and fitted bigger ones that were up to the job.

Suppose he was told that 10KW heater would be required to do what he wanted and then on installign them, he found that after a while the 5x2KW were no longer 2KW but reduced in power to 700W, would that change any calculation,

Of course?

I'msuggesting if that is the case he'd need 13-14 of thse heaters wouldn't he.

Possibly not, (because if I remember your statement correctly), the
heaters cycle between 700 and 1600W on the upper limit stat and so the
average energy may be able to eventually get the space up to temp.


So, to 'feel the affect' of the heating effect you might be better of
with industrial fan / space heaters or IR heaters etc.

Neither of which are allowed in the teaching lab due to H&S.

Then you are fcuked mate. That or you buy lower wattage rads with a
greater surface area.


When you say 'apart' you just mean the plastic end cover off. ;-)

What plastic end cover ?

Normally the controls / wiring are in a plastic cover of some sort (so
you don't burn yourself when touching it and it's cheaper to make
etc).

thought the plastic would be likely to melt

Never seen a plastic handle on a hot air gun or soldering iron?

Yes but it's insulated from the heat part.

By ... ?


and if I did it would then fail regualtaions as we;d need it PAT tested before it was put back into use.

See above. Not all 'plastics' are created equal mate. ;-)

and I doubt the best plastics are in use in his cheap heater.

So are they melting in front of your eyes?

But in the manual they do list things like the carry handle adn everything else the seem to have missed out the section on how to get to the wiring.

Of course?

Perhaps it;s not user accesable like changing the oil.

Indeed it isn't typically user accessible and will probably to have
some security screws on it to deter you from doing so. Doesn't mean
someone couldn't open one up and work on it though.



So another reason njot to take it apart, I'd prefer that we were supplied with working equipment that was up for the job.

But 'a reason' to take it apart would possibly to prove that it wasn't
wired correctly?

I don;t care. I have 5 of them and of the 3 I tested they all do the same.

So contact the supplier to confirm they are working correctly.


It may be that this entire batch of heaters
have been designed badly or wired incorrectly ... or that there is a
second upper-limit stat (or more likely a thermal fuse) that would
ultimately protect the rad from a real overtemp situation (like if you
covered it in towels, even when only on the 700W element).


Nothing of which help work out how many we need.

That wasn't what I was talking about and couldn't without you telling
us more about the entire scenario

you don't need to know more that is the point.

And that my friend simply highlights your ignorance on the matter. ;-(

It's pretty basic maths and even simplier if you think before calculating.

Then why ask us for help?


(including the thermal values for
the rooms / building etc). I gave you most of the tools, costs and
options within my first few posts and I couldn't do much more without
more information (you know, like knowing the likelihood of us leaving
the EU to be likely to be a 'good thing' or not before deciding to do
it). ;-)

No wonder you can't work it out.

Quite. No one can 'work out' anything without the facts. If you can,
you should be rich.


Perhaps that's why we have 14 due to arrive this week.

It might just be a few more to send back. ;-(

They seem to be working as indicated why would I send them back ?

Because they may not have been designed to work that way?


Maybe they could get a 2-3kw garage / workshop fan heater in to try?

Not allowed in a teaching lab .

Ok.

would be handy as my brother works for clarke and he'd get a 10% discount IIRC.

Ok.

But how do you know what power they are ? in order for your calculations to work.

Stamped on the plate and a function of the supply voltage mate.

See, what you have isn't working as expected.

What you have done is buy a cheap compressor that says it can do X but
you have failed to take notice that it's rated duty cycle is only
50:50 and what timescale's that actually is. My compressor for example
has a 50:50 duty cycle with a 60 minute (max) cycle time.

If you bought a 2kW oil filled radiator that could dump the full 2kW
into it's surroundings at all temperature differentials without
overheating itself, we wouldn't be having this discussion right now.

Cheers, T i m

On Tue, 14 Nov 2017 05:32:35 -0800 (PST), whisky-dave
wrote:

snip

http://wiki.diyfaq.org.uk/index.php/...Worked_Example

Think about it and you'll realise the where the biggest error would be.

Erm yes ...

So where ?

You mate. ;-)




So, you either try stuff (different types / sizes of heater) or buy
some hats, gloves and coats. ;-)

for 420 students yeah great idea.

Sounds like it could be better and cheaper than the non solution you
have now?

Cheers, T i m

On 14/11/2017 11:03, Roger Hayter wrote:
John Rumm wrote:

On 13/11/2017 20:38, Roger Hayter wrote:

It seems he already has as much electrical heating as that
autotransformer will ever supply, and is probably exceeding its ratings.
Perhaps someone who knows where it is could have a quick look and see if
any smoke comes out when the voltage drops to 202V?

ISTR that bigclive did a tear-down on one of those voltage reduction
units. At some load point it actually had relays to bridge itself out of
the supply as a self protection mechanism. So you may find enough load
actually takes it out of circuit.

That sounds a sensible arrangement, But doesn't the marked voltage
drop make it a bit unlikely?

It would depend on where it bridged itself (if it does). It might
already have done that, in which case the measured voltage is even more
worrying!

(I remember once years ago we were installing a small network of
machines in the back of a converted mobile library to make a mobile
training setup. It was winter, so we had a rack of 8 systems running,
and a 2kW fan heater plus 1kW of halogen lighting on the mains supply to
the bus. I remember thinking that the fan heater was a bit feeble for
2kW, but then noticed we had an undervolt warning on the rack mount
UPSs. A quick measurement revealed we actually had something around
190V. It was then that the owner mentioned that he had plugged it into
his greenhouse sockets, since those were closest, and he had wired the
submain to the greenhouse in 50m of spare 1.0mm T&E he had laying about!)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Tuesday, 14 November 2017 14:19:52 UTC, T i m wrote:
On Tue, 14 Nov 2017 05:29:29 -0800 (PST), whisky-dave
wrote:

On Monday, 13 November 2017 17:21:04 UTC, T i m wrote:
On Mon, 13 Nov 2017 08:19:36 -0800 (PST), whisky-dave
wrote:

snip

It seems to trip out at about 98C (halfway up the last fin)
so drops to 700W at that point.

Right, it sounds to me like there is a 100 DegC upper limit stat and
only the heavy heater element is going though it.

So it's not realy a cut-out more like a cut-back.

Well, same thing in this case.

No it's not.

Aren't you the one who seemed to have no idea about any of this?

No I find out by testing not reading the data sheet.
But I can do both, all you can do is read the data sheet.

You do know it has both a cut-out and what I'm refering to as a cut-back.


I am describing the electrical device as being what it is, whilst you
are trying to conflate that and the function you (you believe) you see
it having.

I know what's happening vai experimentation.
You know what should happen hopefully via the data sheet.


So what does a cut-out do.

What it says. It's a thermal switch that cuts out (in this case) when
the temperature reaches a certain point and cuts back in again when
the temperature has dropped back to a certain (lower) point again
(just like a thermostat). You can get them that are wired in reverse
to control cooling fans etc.

So is it a cut-out or a thermostat, you seem to be saying tehy are the same.

Electrically, in this case the result of either 'activating' are the
exact same thing, eg, cutting off the flow of electricity through the
element(s).

But that's not what happens because when left on for 2 hours or more it seems when it cuts out the heater still consumes 700 watts.

This is what they call the Overheat protection it switches back to 700W.
So if this heater is left on it;s doen;t produce 2KW of heat it doesn't consume 2KW of electrical power it drops to 700W so effectively a 700W heater after two hours NOT a 2KW heater which is what most would assume as it's written on the box and the unit.



The cut-out is the Safety tip over switch, which acutally does cut out or off the electicity supply to the heater giving a reading of 0 Watts.



So you can't tell the differnce between those labels is that it. ?
Thermostat, cut-out, resettable fuse.

What? As you don't want to open a unit up and without recourse to a
wiring diagram you would (normally) have no idea which one had
operated if the unit had gone off (as they are all usually in series).
ITRW, if you adjust the main thermostat and it all comes back on, of
leave it to cool down a bit and it comes back on, then the thermal
fuse hasn't blown.

Not blown but reset but rarely happens it seems, the only sure way of getting the heater to again comnsume 2KW is to use a cold air blower (I have another fan heater) to blow cool air over the fins of the 2KW heater.


Yes, where the 'overheat protection' is provided by an overtemp /
thermal / cut-out / switch *and / plus* a one way (non-resettable),
thermal fuse.

As I thought you can;t tell teh difernce between these terms a thermostat is the same as a cut-out.

Are you now just trolling mate?

All I'm saying is a 2KW heater won't consume 2KW if yuo leave it on 'full' power it will drop to 700W so if you're calculating how much heat this unit will give out don't assume you'll always get 2KW because after 2 hours you won't it'll switch down to 700W.

I;m sorry you are finding this difficult to understand but it really isn't that difficult.



What measurements, most situations you decide what you want before taking measurements, because yuo buy based on teh specifications of the product.

Not in this case you shouldn't (tail wagging the dog) and John has
explained the process clearly enough elsewhere.

And that would fail in this case.



What you can measure (and it seems like you have been
able to do that bit) you can manage. ;-)

Yep, far better than those using theory.

But only as an 'observation'. You may now have a large quantity of
useless heaters on your hands.

and even more on there way it seems.
But I don't believe they are useless if you understand how they work.



You bought a car to tow a trailer but with no idea how big the trailer
was.

I know how big the trailer is I just didn't expect the car to go from say 2000 HP to 700 HP.

Does your car do that ?

would a 700 HP car take the same time to pull the trailer as a 2000 HP if you kept yuor foot down on the accelerator ?
I'd assume NOT but you seem to think it would, and I don't understand why.



You would have to decide that based on other factors that you haven't
yet covered (less I missed or forgot), like the need / usage,
environment (building type, thermal characteristics etc).

Yes and those were prettyy much fixed when it was built,

Indeed?

Yes just like you're trailer would most likely have a fixed weight.


so how would an engineer predict what sort of heater and what power would be required ?

See Johns replies for an answer on those.

doesnt give the answer and shows exactly what I predict a wrong result due to lack of actual knowledge.



Like, my mate used a waste oil burning space hearer (blown air) in his
garage but it got old and I think they banned them (or were going to
if not heavily updated etc). He got the gas board in and (long short),
much to my mates questioning, they fitted two blown air gas heaters
that were never going to be up to the job. The sales rep suggested he
set the timer to come on at say 6am so the place would be warm for
8am, completely ignoring that the first thing my mate typically did
was open up the end of the garage to move cars in and out (and in so
doing losing any heat). So, they eventually ripped out the new units
and fitted bigger ones that were up to the job.

Suppose he was told that 10KW heater would be required to do what he wanted and then on installign them, he found that after a while the 5x2KW were no longer 2KW but reduced in power to 700W, would that change any calculation,

Of course?

AT LAST the pennies dropped.

So can you show me where this is indicated on the web site. ?
PLease make sure you chek all links before answering.

http://cpc.farnell.com/pro-elec/pel0...ack/dp/HG00575


http://www.farnell.com/datasheets/2339828.pdf

http://www.easyflip.co.uk/CPC_Digita...gue/?page=1906

On Tue, 14 Nov 2017 09:14:55 -0800 (PST), whisky-dave
wrote:

snip

Aren't you the one who seemed to have no idea about any of this?

No I find out by testing not reading the data sheet.

Because you have it in front of you and don't understand the data
sheet?

But I can do both, all you can do is read the data sheet.

Yes, because I don't have a rad in front of me (doh!). When I bought a
new rad last year (well, 4 in fact) I did *exactly* what I suggested
and took the end off one and checked out the wiring (and measured the
function). That's how I *know* how yours is doing what it does and you
don't.

You do know it has both a cut-out and what I'm refering to as a cut-back.

Ok, so let's agree it has a sneekt, a plookert and don't forget the
cleep (should the other two fail). See, we can both make sh1t up for
stuff!

It has a thermostat, an overtemp switch / cutout and a thermal fuse.
These are the actual terms people who know what they are talking about
use to ensure they all understand each other.

https://en.wikipedia.org/wiki/Thermostat
https://en.wikipedia.org/wiki/Therma...Thermal_switch
https://en.wikipedia.org/wiki/Therma...f#Thermal_fuse

"A thermal switch (sometimes thermal reset or thermal cutout)", no
mention of a 'thermal cut-back' notice.



I am describing the electrical device as being what it is, whilst you
are trying to conflate that and the function you (you believe) you see
it having.

I know what's happening vai experimentation.

Noo, you observed some effects and others explained what was
happening.

You know what should happen hopefully via the data sheet.

I've never seen the data sheets. I *know* what is happening from
practical contact with such systems and knowledge of the subject.


So what does a cut-out do.

What it says. It's a thermal switch that cuts out (in this case) when
the temperature reaches a certain point and cuts back in again when
the temperature has dropped back to a certain (lower) point again
(just like a thermostat). You can get them that are wired in reverse
to control cooling fans etc.

So is it a cut-out or a thermostat, you seem to be saying tehy are the same.

Electrically, in this case the result of either 'activating' are the
exact same thing, eg, cutting off the flow of electricity through the
element(s).

But that's not what happens because when left on for 2 hours or more it seems when it cuts out the heater still consumes 700 watts.

I know, and I'm not going to explain to you *again* why that happens.

This is what they call the Overheat protection it switches back to 700W.

So it seems.

So if this heater is left on it;s doen;t produce 2KW of heat it doesn't consume 2KW of electrical power it drops to 700W

No, it doesn't consume nor (therefore) give off 2kW of heat because
the supply voltage won't allow it to.

so effectively a 700W heater after two hours NOT a 2KW heater which is what most would assume as it's written on the box and the unit.

Not quite. When you first turn it on and with the thermostat turned to
max and both switches on and plugged into a 240V supply, what current
would it draw and therefore what power would it consume ?



The cut-out is the Safety tip over switch,

No, there *is a* safety cut-out that (de-)activates when the heater
isn't standing upright.

which acutally does cut out or off the electicity supply to the heater giving a reading of 0 Watts.

Yes, that is *another* safety function and only relevant to the
discussion if you knock the heater over. It cuts the power to 0, just
as the main thermostat does.



So you can't tell the differnce between those labels is that it. ?
Thermostat, cut-out, resettable fuse.

What? As you don't want to open a unit up and without recourse to a
wiring diagram you would (normally) have no idea which one had
operated if the unit had gone off (as they are all usually in series).
ITRW, if you adjust the main thermostat and it all comes back on, of
leave it to cool down a bit and it comes back on, then the thermal
fuse hasn't blown.

Not blown but reset but rarely happens it seems,

They are not generally self resetting.

so the only sure way of getting the heater to again comnsume 2KW is to use a cold air blower (I have another fan heater) to blow cool air over the fins of the 2KW heater.

Yup, because as I explained elsewhere, the radiator is unable to
dissipate sufficient heat fast enough and so 'overheats' and trips
itself (or the just main element in your case it seems) out.


Yes, where the 'overheat protection' is provided by an overtemp /
thermal / cut-out / switch *and / plus* a one way (non-resettable),
thermal fuse.

As I thought you can;t tell teh difernce between these terms a thermostat is the same as a cut-out.

Are you now just trolling mate?

All I'm saying is a 2KW heater won't consume 2KW if yuo leave it on 'full' power

It will if on a suitably rated supply and does initially.

it will drop to 700W

So must have been higher (than 700W) or it wouldn't 'drop' would it?

so if you're calculating how much heat this unit will give out don't assume you'll always get 2KW because after 2 hours you won't it'll switch down to 700W.

No, it won't 'switch down to 700W', it cycles between 700 and 2000W
(~1600W because of your low voltage) indefinitely until the
temperature set by the thermostat is met.

I;m sorry you are finding this difficult to understand but it really isn't that difficult.

Bwhahahaha. Oh the irony!

Ok, let me see if you can understand a solution I am working on around
the very same issues.

I have a mini oil-filled 450W, thermostatically controlled radiator
(well, 4 actually) that do *exactly* the same thing as yours in that
they cycle on the overtemp stat (because the energy in is the energy
out).

So, I was going to design and build a controller that uses an Arduino
Nano, a triac and a couple of external temperature sensors to properly
'manage' the heater. The std heater plugs into my solution.

Temp sensor 1 will be clipped to the heater and will moderate the max
temp of the rad to less than the internal overtemp switch.

Temp sensor 2 will measure the ambient temperature of the room.

At start up, both sensors are read and if the value of either is above
their desired setting, the heater stays off.

If the Temps sensor 2 indicates it is lower than the desired
temperature it will apply power to the heater and the maximum
temperature of the heater will be managed by the Arduino in either PWM
(possibly via a PID) or bang bang with some allowance for thermal
overshoot.

Once the room heats up and reaches the setting for Sensor 2, the
heater is turned off again.

The *reason* for doing that is we only need a small heater in the
bedroom but both the overtemp stat and thermostat are quite noisy,
hence the electronic solution.

As an alternative / experiment I intend wiring two heaters in
*series*, as that way I will still have my 450W (2 x 225) but the
heaters may then be able to dissipate the lower energy without cycling
on the overtemp stat. Then I could use a std plug-in electronic timer
/ stat and save all the building bit (I'd just need to set the rad
stats to a level *above* my desired room temperature).

So, do you still think I don't understand exactly what is going on
with your setup?



What measurements, most situations you decide what you want before taking measurements, because yuo buy based on teh specifications of the product.

Not in this case you shouldn't (tail wagging the dog) and John has
explained the process clearly enough elsewhere.

And that would fail in this case.

Doing the calculations should be step one mate, not step two. What has
actually failed is the particular solution you are trying to implement
(and possibly including a design / wiring fault).



What you can measure (and it seems like you have been
able to do that bit) you can manage. ;-)

Yep, far better than those using theory.

But only as an 'observation'. You may now have a large quantity of
useless heaters on your hands.

and even more on there way it seems.

Quite.

But I don't believe they are useless if you understand how they work.

Bwhahaha ... I understand how they work mate ... ;-)



You bought a car to tow a trailer but with no idea how big the trailer
was.

I know how big the trailer is I just didn't expect the car to go from say 2000 HP to 700 HP.

And if it did you would contact the supplier and ask why eh?

snip

I'd assume NOT but you seem to think it would, and I don't understand why.

I know you don't, in spite of me explaining it several times and
suggesting you check one yourself (wiring) and contact the supplier /
manufacturer.

I'll try one more time and in simple terms even you should be able to
understand ...

(Potentially ...) The heater has the ability to give off something
*less* than the maximum it can consume (even when that is only 1600W)
because the heater power is too big for it's surface area. The end.

So, if you stuck a diode in series with the heater and reduced it's
power by 50%, the chances are it wouldn't 'cut out' (the main element)
.... cut-back in power (because of how it's wired) and you would be
happy.


You would have to decide that based on other factors that you haven't
yet covered (less I missed or forgot), like the need / usage,
environment (building type, thermal characteristics etc).

Yes and those were prettyy much fixed when it was built,

Indeed?

Yes just like you're trailer would most likely have a fixed weight.

Yup ... but you still don't know what that is do you.


so how would an engineer predict what sort of heater and what power would be required ?

See Johns replies for an answer on those.

doesnt give the answer and shows exactly what I predict a wrong result due to lack of actual knowledge.

No, it gives you the number you do still need to allow you to
determine if the goal is achievable or not.



Like, my mate used a waste oil burning space hearer (blown air) in his
garage but it got old and I think they banned them (or were going to
if not heavily updated etc). He got the gas board in and (long short),
much to my mates questioning, they fitted two blown air gas heaters
that were never going to be up to the job. The sales rep suggested he
set the timer to come on at say 6am so the place would be warm for
8am, completely ignoring that the first thing my mate typically did
was open up the end of the garage to move cars in and out (and in so
doing losing any heat). So, they eventually ripped out the new units
and fitted bigger ones that were up to the job.

Suppose he was told that 10KW heater would be required to do what he wanted and then on installign them, he found that after a while the 5x2KW were no longer 2KW but reduced in power to 700W, would that change any calculation,

Of course?

AT LAST the pennies dropped.

With you, hopefully! It wouldn't change the calcs for the requirement
but it would change the calcs for the / your solution.

So can you show me where this is indicated on the web site. ?

Ok ...

PLease make sure you chek all links before answering.

Yes Sir! (P.s. Do you have my bank details to pay me for doing this
for you)?

http://cpc.farnell.com/pro-elec/pel0...ack/dp/HG00575


http://www.farnell.com/datasheets/2339828.pdf

As I have explained (at length):

"This heater includes an overheat protection system that shuts off the
heater when parts of the heater are getting excessively hot."

Except is doesn't does it, it cuts *part* of the heater off (also as I
have explained at length).

http://www.easyflip.co.uk/CPC_Digita...gue/?page=1906

You have a oil filled radiator that has the potential of giving 2000w
worth of heat continuously, as long as the heater is in a cold enough
environment (or the convection efficiency improved by putting it in an
airflow) to ensure the radiator doesn't 'overheat'.

HTH (finally).

Cheers, T i m

On Tuesday, 14 November 2017 16:53:40 UTC, John Rumm wrote:
On 14/11/2017 11:03, Roger Hayter wrote:
John Rumm wrote:

On 13/11/2017 20:38, Roger Hayter wrote:

It seems he already has as much electrical heating as that
autotransformer will ever supply, and is probably exceeding its ratings.
Perhaps someone who knows where it is could have a quick look and see if
any smoke comes out when the voltage drops to 202V?

ISTR that bigclive did a tear-down on one of those voltage reduction
units. At some load point it actually had relays to bridge itself out of
the supply as a self protection mechanism. So you may find enough load
actually takes it out of circuit.

That sounds a sensible arrangement, But doesn't the marked voltage
drop make it a bit unlikely?

It would depend on where it bridged itself (if it does). It might
already have done that, in which case the measured voltage is even more
worrying!

doesn't worry me in the least because I expected it.
That's the advantage of understanding both theory and the real world.

On Wed, 15 Nov 2017 03:30:12 -0800 (PST), whisky-dave
wrote:

On Tuesday, 14 November 2017 16:53:40 UTC, John Rumm wrote:
On 14/11/2017 11:03, Roger Hayter wrote:
John Rumm wrote:

On 13/11/2017 20:38, Roger Hayter wrote:

It seems he already has as much electrical heating as that
autotransformer will ever supply, and is probably exceeding its ratings.
Perhaps someone who knows where it is could have a quick look and see if
any smoke comes out when the voltage drops to 202V?

ISTR that bigclive did a tear-down on one of those voltage reduction
units. At some load point it actually had relays to bridge itself out of
the supply as a self protection mechanism. So you may find enough load
actually takes it out of circuit.

That sounds a sensible arrangement, But doesn't the marked voltage
drop make it a bit unlikely?

It would depend on where it bridged itself (if it does). It might
already have done that, in which case the measured voltage is even more
worrying!

doesn't worry me in the least because I expected it.

I don't think you can be sure exactly where the voltage drop is coming
from though can (even) you?

That's the advantage of understanding both theory and the real world.

I'll look forward to that moment for you. ;-)

Cheers, T i m

On Tuesday, 14 November 2017 18:39:54 UTC, T i m wrote:
On Tue, 14 Nov 2017 09:14:55 -0800 (PST), whisky-dave
wrote:

snip

Aren't you the one who seemed to have no idea about any of this?

No I find out by testing not reading the data sheet.

Because you have it in front of you and don't understand the data
sheet?

I understand some of it.
safety information .

1 / Check that the voltage indicated on the rating plate corresponds with that of the local network before connecting the before connecting the applince to the mains supply.

I don't think they are using the term network correct or not as we use it.
Our netword uses cat 6 cable perhaps 6e installed y the networks team who install network cable but they aren't qualified electricians which are a differnt set of individuals as our plumbers and gas workers are.

I understand and can translate the data sheet can you ?



But I can do both, all you can do is read the data sheet.

Yes, because I don't have a rad in front of me (doh!). When I bought a
new rad last year (well, 4 in fact) I did *exactly* what I suggested
and took the end off one and checked out the wiring (and measured the
function). That's how I *know* how yours is doing what it does and you
don't.

I do I can't take them apart they do NOT belong to me or my department.
we have been lent them. I do NOT believe that they have a wiring fault.




It has a thermostat, an overtemp switch / cutout and a thermal fuse.

I do NOT know if it has a thermal fuse did you see it mentioned anywhere ?

These are the actual terms people who know what they are talking about
use to ensure they all understand each other.

https://en.wikipedia.org/wiki/Thermostat
https://en.wikipedia.org/wiki/Therma...Thermal_switch
https://en.wikipedia.org/wiki/Therma...f#Thermal_fuse

None of which appear in the data sheet.


"A thermal switch (sometimes thermal reset or thermal cutout)", no
mention of a 'thermal cut-back' notice.


Which page is that mentioned on ?


I am describing the electrical device as being what it is, whilst you
are trying to conflate that and the function you (you believe) you see
it having.

I know what's happening vai experimentation.

Noo, you observed some effects and others explained what was
happening.

I know what's happening but I didnlt get that knowledge from the data sheet..


You know what should happen hopefully via the data sheet.

I've never seen the data sheets.

perhaps it's time you loked then.

I *know* what is happening from
practical contact with such systems and knowledge of the subject.


Me too.



But that's not what happens because when left on for 2 hours or more it seems when it cuts out the heater still consumes 700 watts.

I know, and I'm not going to explain to you *again* why that happens.

This is what they call the Overheat protection it switches back to 700W.

So it seems.

At last.


So if this heater is left on it;s doen;t produce 2KW of heat it doesn't consume 2KW of electrical power it drops to 700W

No, it doesn't consume nor (therefore) give off 2kW of heat because
the supply voltage won't allow it to.

The supply will allow it, the supply has little to nothing to do with it, it is plugged into the mains supply.


so effectively a 700W heater after two hours NOT a 2KW heater which is what most would assume as it's written on the box and the unit.

Not quite. When you first turn it on and with the thermostat turned to
max and both switches on and plugged into a 240V supply, what current
would it draw and therefore what power would it consume ?

In my office it consumers about ~8amps on switch on. At that moment the voltage is beTween 211 & 213 .
Don;t forget the data sheep spoec that says any voltage from 220-240 the rad will comsume 2KW ;-P



What would you expect a heater with a label that says 220-240 50Hz 2000W to do ?



The cut-out is the Safety tip over switch,

No, there *is a* safety cut-out that (de-)activates when the heater
isn't standing upright.

Yep pretty much says that in the manual and I've tried it and it works
it goes dwon to 0W consumtion when laying on it's side or rather it switchees out at about 40 degrees.


which acutally does cut out or off the electicity supply to the heater giving a reading of 0 Watts.

Yes, that is *another* safety function and only relevant to the
discussion if you knock the heater over. It cuts the power to 0, just
as the main thermostat does.

Yes I know, I've know that all along. I've had one in my office for about 2 years now.




So you can't tell the differnce between those labels is that it. ?
Thermostat, cut-out, resettable fuse.

What? As you don't want to open a unit up and without recourse to a
wiring diagram you would (normally) have no idea which one had
operated if the unit had gone off (as they are all usually in series).
ITRW, if you adjust the main thermostat and it all comes back on, of
leave it to cool down a bit and it comes back on, then the thermal
fuse hasn't blown.

Not blown but reset but rarely happens it seems,

They are not generally self resetting.

But something is, otherwise it wouldnlt go back to 1.7KW .



so the only sure way of getting the heater to again comnsume 2KW is to use a cold air blower (I have another fan heater) to blow cool air over the fins of the 2KW heater.

Yup, because as I explained elsewhere, the radiator is unable to
dissipate sufficient heat fast enough and so 'overheats' and trips
itself (or the just main element in your case it seems) out.

Yes trips out and auto-resets yes. And while in this state it does NOT give out 2KW of heat.




Are you now just trolling mate?

All I'm saying is a 2KW heater won't consume 2KW if yuo leave it on 'full' power

It will if on a suitably rated supply and does initially.

It's always been on a suitabley rated supply.

and does initially.

So the penny has started to drop at long last.




it will drop to 700W

So must have been higher (than 700W) or it wouldn't 'drop' would it?

well done you're almost there now.


so if you're calculating how much heat this unit will give out don't assume you'll always get 2KW because after 2 hours you won't it'll switch down to 700W.

No, it won't 'switch down to 700W', it cycles between 700 and 2000W
(~1600W because of your low voltage) indefinitely until the
temperature set by the thermostat is met.

Nothing to do with the thermostat (the thinbg with the knob on it) that remains at maxium setting .


I;m sorry you are finding this difficult to understand but it really isn't that difficult.

Bwhahahaha. Oh the irony!



Ok, let me see if you can understand a solution I am working on around
the very same issues.

I have a mini oil-filled 450W, thermostatically controlled radiator
(well, 4 actually) that do *exactly* the same thing as yours in that
they cycle on the overtemp stat (because the energy in is the energy
out).

Why is the energy in is the energy out is it becazuse yuor supply isn't up to standard ?

I wouldn't have thought so myself.



So, I was going to design and build a controller that uses an Arduino
Nano, a triac and a couple of external temperature sensors to properly
'manage' the heater. The std heater plugs into my solution.

Are you suggeting that the thermostats on those heaters don't work ?


Temp sensor 1 will be clipped to the heater and will moderate the max
temp of the rad to less than the internal overtemp switch.

why bother.


Temp sensor 2 will measure the ambient temperature of the room.

At start up, both sensors are read and if the value of either is above
their desired setting, the heater stays off.

If the Temps sensor 2 indicates it is lower than the desired
temperature it will apply power to the heater and the maximum
temperature of the heater will be managed by the Arduino in either PWM
(possibly via a PID) or bang bang with some allowance for thermal
overshoot.

Once the room heats up and reaches the setting for Sensor 2, the
heater is turned off again.

Is this because the thermostts don't work ?
You see most people buying these heaters arent; likey to set up an arduino adn why you'd use a nano I don't know I'd use one of the new Arduino PRIMO so you can control it wirelessly.



The *reason* for doing that is we only need a small heater in the
bedroom but both the overtemp stat and thermostat are quite noisy,
hence the electronic solution.

well noise isn't our concern the amount of heat supplied is more important.


As an alternative / experiment I intend wiring two heaters in
*series*, as that way I will still have my 450W (2 x 225) but the
heaters may then be able to dissipate the lower energy without cycling
on the overtemp stat. Then I could use a std plug-in electronic timer
/ stat and save all the building bit (I'd just need to set the rad
stats to a level *above* my desired room temperature).

So what made you choose 450W heater ?
What's wrong with 2KW or 2.5KW which I use at home.


So, do you still think I don't understand exactly what is going on
with your setup?

Yes I still think that, going by what you've said.



What measurements, most situations you decide what you want before taking measurements, because yuo buy based on teh specifications of the product.

Not in this case you shouldn't (tail wagging the dog) and John has
explained the process clearly enough elsewhere.

And that would fail in this case.

Doing the calculations should be step one mate, not step two.

Shouldn't be a step for me or anyone else here.
Can you show yuor calculations for step 1 ?


What has
actually failed is the particular solution you are trying to implement
(and possibly including a design / wiring fault).

Design fault YES (at last) wiring faulty NO.


But I don't believe they are useless if you understand how they work.

Bwhahaha ... I understand how they work mate ... ;-)

Not shown much evidence of that yet, well not a true understanding, perhaps a casual users understanding like those that ordered them who have degrees in managment but can't tell a plug from a socket.




You bought a car to tow a trailer but with no idea how big the trailer
was.

I know how big the trailer is I just didn't expect the car to go from say 2000 HP to 700 HP.

And if it did you would contact the supplier and ask why eh?

That would depend on the car and the cost of that car.



I'd assume NOT but you seem to think it would, and I don't understand why.

I know you don't, in spite of me explaining it several times and
suggesting you check one yourself (wiring) and contact the supplier /
manufacturer.

Not interested when 3 of the 5 all do the same just like it says in the supplied manual.


I'll try one more time and in simple terms even you should be able to
understand ...

You've just lost the plot that's all.

\

(Potentially ...) The heater has the ability to give off something
*less* than the maximum it can consume (even when that is only 1600W)
because the heater power is too big for it's surface area. The end.

Well ****ing done at last, so how would you calculate how many heaters would be needed if the heaters you brought can only dissapate the stated heat for about 2 hours then switch down to a 1/3 of their rated value ?

Explain it to me, if you do really understand this.



So, if you stuck a diode in series with the heater and reduced it's
power by 50%, the chances are it wouldn't 'cut out' (the main element)
... cut-back in power (because of how it's wired) and you would be
happy.

I would NOT be happy buying a 2KW heater just to reduce it to 1KW with a diode in the hope it didn't drop to 700W.

The thermostat is meant to control both the amount of current heating the eliment and therfore the amount of heat generated or whay donlt yuo explain what the thermostat is for.
If yuo look in ther manual it tells you how to set these units up using the thermostat rather than the over heat protection or the trip out.





so how would an engineer predict what sort of heater and what power would be required ?

See Johns replies for an answer on those.

doesnt give the answer and shows exactly what I predict a wrong result due to lack of actual knowledge.

No, it gives you the number you do still need to allow you to
determine if the goal is achievable or not.

So how woul yuo work that out if 2KW heaters all reduce to 700W after 2 hours ?
This is the key point the point you keep missing.

Lets try this again a 2KW heater is consuming 700W of electrical power so I assume if is giving nout less than 2KW of heat.
Unless of course tyuo believe these £25 rads are the answer to propectual montion or similar where 700W of electrical power can produce the same heating effect as 2KW of electrical power.

Is that really what you believe ?

Suppose he was told that 10KW heater would be required to do what he wanted and then on installign them, he found that after a while the 5x2KW were no longer 2KW but reduced in power to 700W, would that change any calculation,

Of course?

AT LAST the pennies dropped.

With you, hopefully! It wouldn't change the calcs for the requirement

Yes it would change what was needed.

but it would change the calcs for the / your solution.

So can you show me where this is indicated on the web site. ?

Ok ...

PLease make sure you chek all links before answering.

Yes Sir! (P.s. Do you have my bank details to pay me for doing this
for you)?

Not that'll post.


http://cpc.farnell.com/pro-elec/pel0...ack/dp/HG00575


http://www.farnell.com/datasheets/2339828.pdf

As I have explained (at length):

"This heater includes an overheat protection system that shuts off the
heater when parts of the heater are getting excessively hot."

and that will happen nif yuo have the heater on full.
So a 2KW heater after 2 hours turns into a 700W heater how many times do you need telling ?



Except is doesn't does it, it cuts *part* of the heater off (also as I
have explained at length).

http://www.easyflip.co.uk/CPC_Digita...gue/?page=1906

You have a oil filled radiator that has the potential of giving 2000w

exactly a potential that is only reached for 2 hours for the rest of the day/night it will be a 700W heater have you got that yet.


worth of heat continuously, as long as the heater is in a cold enough
environment (or the convection efficiency improved by putting it in an
airflow) to ensure the radiator doesn't 'overheat'.

so the heater can't or isnlt cable of truelly dissapating the heat for more than two hours so it turns into a 700W heater which for the rest of the day only dissapates 700W of heat have you understood this yet.

A 2KW heater is a 2KW heater for 2 hours then it 'morphes' into a 700W heater
Why is this difficult to understand, if I want a 700W heater I;d buy a cheaper smaller heater.


HTH (finally).

Cheers, T i m

On Wednesday, 15 November 2017 11:55:42 UTC, T i m wrote:
On Wed, 15 Nov 2017 03:30:12 -0800 (PST), whisky-dave


It would depend on where it bridged itself (if it does). It might
already have done that, in which case the measured voltage is even more
worrying!

doesn't worry me in the least because I expected it.

I don't think you can be sure exactly where the voltage drop is coming
from though can (even) you?

No but againn I donlt care.
We have those 3 pin sockets in the lab that supply power that are just like those in everyones house, hwo often to yuo worry whether the volatge at that point is 200V or 240V ?
How often to you measure it to check, before vacuuming do you check the voltage before or during vacuuming if not why not ?

On Wed, 15 Nov 2017 05:38:07 -0800 (PST), whisky-dave
wrote:

On Tuesday, 14 November 2017 18:39:54 UTC, T i m wrote:
On Tue, 14 Nov 2017 09:14:55 -0800 (PST), whisky-dave
wrote:

snip

Aren't you the one who seemed to have no idea about any of this?

No I find out by testing not reading the data sheet.

Because you have it in front of you and don't understand the data
sheet?

I understand some of it.
safety information .

1 / Check that the voltage indicated on the rating plate corresponds with that of the local network before connecting the before connecting the applince to the mains supply.

I don't think they are using the term network correct or not as we use it.

They mean (clearly) 'The power distribution network'.

Our netword uses cat 6 cable perhaps 6e installed y the networks team who install network cable but they aren't qualified electricians which are a differnt set of individuals as our plumbers and gas workers are.

Whoosh.

I understand and can translate the data sheet can you ?

It doesn't look like it does it?


But I can do both, all you can do is read the data sheet.

Yes, because I don't have a rad in front of me (doh!). When I bought a
new rad last year (well, 4 in fact) I did *exactly* what I suggested
and took the end off one and checked out the wiring (and measured the
function). That's how I *know* how yours is doing what it does and you
don't.

I do I can't take them apart they do NOT belong to me or my department.

I know.

we have been lent them.

Ok.

I do NOT believe that they have a wiring fault.

I'm not interested in your 'beliefs' mate, just the facts. ;-)


It has a thermostat, an overtemp switch / cutout and a thermal fuse.

I do NOT know if it has a thermal fuse did you see it mentioned anywhere ?

No, but every similar device I've ever opened has had one and I'm not
sure it would get certification without.

These are the actual terms people who know what they are talking about
use to ensure they all understand each other.

https://en.wikipedia.org/wiki/Thermostat
https://en.wikipedia.org/wiki/Therma...Thermal_switch
https://en.wikipedia.org/wiki/Therma...f#Thermal_fuse

None of which appear in the data sheet.

Two of them do, just that you don't understand enough about it all to
realise it. ;-(


"A thermal switch (sometimes thermal reset or thermal cutout)", no
mention of a 'thermal cut-back' notice.


Which page is that mentioned on ?

The datasheet *you* linked to.


I am describing the electrical device as being what it is, whilst you
are trying to conflate that and the function you (you believe) you see
it having.

I know what's happening vai experimentation.

Noo, you observed some effects and others explained what was
happening.

I know what's happening but I didnlt get that knowledge from the data sheet.

I repeat, you don't know what is happening, you only report what you
see happening (and are still asking us *why*).


You know what should happen hopefully via the data sheet.

I've never seen the data sheets.

perhaps it's time you loked then.

You think?

I *know* what is happening from
practical contact with such systems and knowledge of the subject.


Me too.

You are funny mate. ;-)



But that's not what happens because when left on for 2 hours or more it seems when it cuts out the heater still consumes 700 watts.

I know, and I'm not going to explain to you *again* why that happens.

This is what they call the Overheat protection it switches back to 700W.

So it seems.

At last.

Erm ... I was telling you what was happing from my first post!


So if this heater is left on it;s doen;t produce 2KW of heat it doesn't consume 2KW of electrical power it drops to 700W

No, it doesn't consume nor (therefore) give off 2kW of heat because
the supply voltage won't allow it to.

The supply will allow it, the supply has little to nothing to do with it, it is plugged into the mains supply.

Aw bless ... it's like trying to explain it all to a child. ;-)


so effectively a 700W heater after two hours NOT a 2KW heater which is what most would assume as it's written on the box and the unit.

Not quite. When you first turn it on and with the thermostat turned to
max and both switches on and plugged into a 240V supply, what current
would it draw and therefore what power would it consume ?

In my office it consumers about ~8amps on switch on. At that moment the voltage is beTween 211 & 213 .

So that's around 1700W. Can you just have the NoII element on without
the NoI and if so, I wonder if it would then still cycle on the
overtemp stat?

Don;t forget the data sheep spoec that says any voltage from 220-240 the rad will comsume 2KW ;-P

The good news is at least you (now seem to) realise that is
impossible. ;-)


What would you expect a heater with a label that says 220-240 50Hz 2000W to do ?

Consume circa 2000W at 240V and, if the surface area isn't big enough
to dissipate all that energy, get overly hot and trip out on it's
overtemp stat, even when the main stat is still calling for heat.
However, I think I would expect it to cut out entirely, not back to
the low power element.

The cut-out is the Safety tip over switch,

No, there *is a* safety cut-out that (de-)activates when the heater
isn't standing upright.

Yep pretty much says that in the manual and I've tried it and it works
it goes dwon to 0W consumtion when laying on it's side or rather it switchees out at about 40 degrees.

Yes, you said. If not a physical button underneath, it would often be
a ball, cup and micro switch arrangement.


which acutally does cut out or off the electicity supply to the heater giving a reading of 0 Watts.

Yes, that is *another* safety function and only relevant to the
discussion if you knock the heater over. It cuts the power to 0, just
as the main thermostat does.

Yes I know, I've know that all along. I've had one in my office for about 2 years now.

You said 'The cut-out is the Safety tip over switch'. No one was
talking about such things (but you). I was talking of the 'overtemp
safety cutout'. You got confused.




So you can't tell the differnce between those labels is that it. ?
Thermostat, cut-out, resettable fuse.

What? As you don't want to open a unit up and without recourse to a
wiring diagram you would (normally) have no idea which one had
operated if the unit had gone off (as they are all usually in series).
ITRW, if you adjust the main thermostat and it all comes back on, of
leave it to cool down a bit and it comes back on, then the thermal
fuse hasn't blown.

Not blown but reset but rarely happens it seems,

They are not generally self resetting.

But something is, otherwise it wouldnlt go back to 1.7KW .

Yes (FFS), the overtemp switch, *not* the overtemp fuse. Really, is
this all that difficult for you?



so the only sure way of getting the heater to again comnsume 2KW is to use a cold air blower (I have another fan heater) to blow cool air over the fins of the 2KW heater.

Yup, because as I explained elsewhere, the radiator is unable to
dissipate sufficient heat fast enough and so 'overheats' and trips
itself (or the just main element in your case it seems) out.

Yes trips out and auto-resets yes.

Yes, because it's an 'overtemp stat', not an 'overtemp fuse'.

And while in this state it does NOT give out 2KW of heat.

No, really, why didn't you say earlier? Hey, I wonder why it doesn't
.... ?




Are you now just trolling mate?

All I'm saying is a 2KW heater won't consume 2KW if yuo leave it on 'full' power

It will if on a suitably rated supply and does initially.

It's always been on a suitabley rated supply.

Not for 2kW output it hasn't.

and does initially.

So the penny has started to drop at long last.

Nope, obviously it hasn't (with you). ;-(


it will drop to 700W

So must have been higher (than 700W) or it wouldn't 'drop' would it?

well done you're almost there now.

Bless.


so if you're calculating how much heat this unit will give out don't assume you'll always get 2KW because after 2 hours you won't it'll switch down to 700W.

No, it won't 'switch down to 700W', it cycles between 700 and 2000W
(~1600W because of your low voltage) indefinitely until the
temperature set by the thermostat is met.

Nothing to do with the thermostat (the thinbg with the knob on it) that remains at maxium setting .

Where did I mention anything about the thermostat affecting your
results? What part of 'indefinitely *until* the temperature set by the
thermostat is met' don't you get?

Clue, AFAIK, the temperature set by the main stat has *never* been met
yet.


I;m sorry you are finding this difficult to understand but it really isn't that difficult.

Bwhahahaha. Oh the irony!



Ok, let me see if you can understand a solution I am working on around
the very same issues.

I have a mini oil-filled 450W, thermostatically controlled radiator
(well, 4 actually) that do *exactly* the same thing as yours in that
they cycle on the overtemp stat (because the energy in is the energy
out).

Why is the energy in is the energy out is it becazuse yuor supply isn't up to standard ?

No, quite the opposite in fact (so well done for getting something
else completely wrong) ... it's because of the radiators inability to
dissipate the energy consumed as fast as it consumes it (just the same
as the ones you have there).

I wouldn't have thought so myself.

Of course you would ... and been wrong (again).



So, I was going to design and build a controller that uses an Arduino
Nano, a triac and a couple of external temperature sensors to properly
'manage' the heater. The std heater plugs into my solution.

Are you suggeting that the thermostats on those heaters don't work ?

Nope.


Temp sensor 1 will be clipped to the heater and will moderate the max
temp of the rad to less than the internal overtemp switch.

why bother.

To make it suitable for a bedroom.


Temp sensor 2 will measure the ambient temperature of the room.

At start up, both sensors are read and if the value of either is above
their desired setting, the heater stays off.

If the Temps sensor 2 indicates it is lower than the desired
temperature it will apply power to the heater and the maximum
temperature of the heater will be managed by the Arduino in either PWM
(possibly via a PID) or bang bang with some allowance for thermal
overshoot.

Once the room heats up and reaches the setting for Sensor 2, the
heater is turned off again.

Is this because the thermostts don't work ?

Nope.

You see most people buying these heaters arent; likey to set up an arduino

I know, especially you eh! ;-)

adn why you'd use a nano

Of course you don't and you haven't asked.

I don't know

I get that!

I'd use one of the new Arduino PRIMO so you can control it wirelessly.

It's background heating mate, I don't really need that.


The *reason* for doing that is we only need a small heater in the
bedroom but both the overtemp stat and thermostat are quite noisy,
hence the electronic solution.

well noise isn't our concern the amount of heat supplied is more important.

No! Why didn't you say that at the beginning! ;-(


As an alternative / experiment I intend wiring two heaters in
*series*, as that way I will still have my 450W (2 x 225) but the
heaters may then be able to dissipate the lower energy without cycling
on the overtemp stat. Then I could use a std plug-in electronic timer
/ stat and save all the building bit (I'd just need to set the rad
stats to a level *above* my desired room temperature).

So what made you choose 450W heater ?

Because it was tiny (in size, just so you don't confuse small size
with low power).

What's wrong with 2KW or 2.5KW which I use at home.

Too big (physically).


So, do you still think I don't understand exactly what is going on
with your setup?

Yes I still think that, going by what you've said.

Bless.



What measurements, most situations you decide what you want before taking measurements, because yuo buy based on teh specifications of the product.

Not in this case you shouldn't (tail wagging the dog) and John has
explained the process clearly enough elsewhere.

And that would fail in this case.

Doing the calculations should be step one mate, not step two.

Shouldn't be a step for me or anyone else here.

That's *exactly* who should be doing it. Or do you think CPC should do
it for you, or someone here?

Can you show yuor calculations for step 1 ?

I don't need to because the heater is more than capable of meeting the
requirements.


What has
actually failed is the particular solution you are trying to implement
(and possibly including a design / wiring fault).

Design fault YES (at last) wiring faulty NO.

Well, one precludes the other (doh). eg (For the hard of thinking), if
it was designed to work like that it could still be a design fault but
then wouldn't be a production wiring fault.


But I don't believe they are useless if you understand how they work.

Bwhahaha ... I understand how they work mate ... ;-)

Not shown much evidence of that yet,

Bwhaha! I explained to you exactly how they work in my first post.

well not a true understanding,

A very detailed understanding in fact.

perhaps a casual users understanding like those that ordered them who have degrees in managment but can't tell a plug from a socket.

Or determine the energy requirements of a space (and why you would
need to) or how a basic electric radiator works?


You bought a car to tow a trailer but with no idea how big the trailer
was.

I know how big the trailer is I just didn't expect the car to go from say 2000 HP to 700 HP.

And if it did you would contact the supplier and ask why eh?

That would depend on the car and the cost of that car.

Irrelevant.



I'd assume NOT but you seem to think it would, and I don't understand why.

I know you don't, in spite of me explaining it several times and
suggesting you check one yourself (wiring) and contact the supplier /
manufacturer.

Not interested when 3 of the 5 all do the same just like it says in the supplied manual.

Where does it explain in the manual that the over temp stay only works
on the bigger element? You didn't even realise what an overtemp stat
was or how or when it worked till I told you! And I'm guessing you
have never heard of a 'production / batch fault' that could affect
*thousands* of items?


I'll try one more time and in simple terms even you should be able to
understand ...

You've just lost the plot that's all.

Awww bless. ;-)

\

(Potentially ...) The heater has the ability to give off something
*less* than the maximum it can consume (even when that is only 1600W)
because the heater power is too big for it's surface area. The end.

Well ****ing done at last, so how would you calculate how many heaters would be needed if the heaters you brought can only dissapate the stated heat for about 2 hours then switch down to a 1/3 of their rated value ?

By measuring their duty cycle at a range of (ambient) temperatures and
taking it from there.

Explain it to me, if you do really understand this.

See above (and there is no *if*).



So, if you stuck a diode in series with the heater and reduced it's
power by 50%, the chances are it wouldn't 'cut out' (the main element)
... cut-back in power (because of how it's wired) and you would be
happy.

I would NOT be happy buying a 2KW heater just to reduce it to 1KW with a diode in the hope it didn't drop to 700W.

I'm not saying you would be happy to do that ... I was just trying to
help you understand the problem.

The thermostat is meant to control both the amount of current heating the eliment and therfore the amount of heat generated or whay donlt yuo explain what the thermostat is for.

Because at the moment, the main thermostat hasn't come into it as the
room hasn't reached the required temperature.

If yuo look in ther manual it tells you how to set these units up using the thermostat rather than the over heat protection or the trip out.

No, does it rolls eyes, I wonder why no one picked up on that
sooner?


so how would an engineer predict what sort of heater and what power would be required ?

See Johns replies for an answer on those.

doesnt give the answer and shows exactly what I predict a wrong result due to lack of actual knowledge.

No, it gives you the number you do still need to allow you to
determine if the goal is achievable or not.

So how woul yuo work that out if 2KW heaters all reduce to 700W after 2 hours ?

Whoosh ...

This is the key point the point you keep missing.

I am missing nothing here mate, only the fact that you are just
trolling?


Lets try this again a 2KW heater is consuming 700W of electrical power so I assume if is giving nout less than 2KW of heat.

Try what again? WTF is it not clear to you yet?

Unless of course tyuo believe these £25 rads are the answer to propectual montion or similar where 700W of electrical power can produce the same heating effect as 2KW of electrical power.

I think nothing of the sort ... luckily I don't need to think
anything, because I *know*.

Is that really what you believe ?

See above.

Suppose he was told that 10KW heater would be required to do what he wanted and then on installign them, he found that after a while the 5x2KW were no longer 2KW but reduced in power to 700W, would that change any calculation,

Of course?

AT LAST the pennies dropped.

With you, hopefully! It wouldn't change the calcs for the requirement

Yes it would change what was needed.

It wouldn't change it, it would allow you to measure / predict it.

but it would change the calcs for the / your solution.

So can you show me where this is indicated on the web site. ?

Ok ...

PLease make sure you chek all links before answering.

Yes Sir! (P.s. Do you have my bank details to pay me for doing this
for you)?

Not that'll post.

No, it was *my* bank details I was offering (feck this is hard work).


http://cpc.farnell.com/pro-elec/pel0...ack/dp/HG00575


http://www.farnell.com/datasheets/2339828.pdf

As I have explained (at length):

"This heater includes an overheat protection system that shuts off the
heater when parts of the heater are getting excessively hot."

and that will happen nif yuo have the heater on full.

It will run at full power till it overheats and then not.

So a 2KW heater after 2 hours turns into a 700W heater how many times do you need telling ?

Just the once mate. How many times do you need the reason explaining
before you understand it?



Except is doesn't does it, it cuts *part* of the heater off (also as I
have explained at length).

http://www.easyflip.co.uk/CPC_Digita...gue/?page=1906

You have a oil filled radiator that has the potential of giving 2000w

exactly a potential that is only reached for 2 hours for the rest of the day/night it will be a 700W heater have you got that yet.

Nope, because that's BS. It will run for a time at full power till it
overheats. Then (in your case, not mine) it will drop back to a lower
power and cool down again. Once it has cool sufficiently (the
hysteresis of the overtemp stat) it will return to full power again.
Got it yet?


worth of heat continuously, as long as the heater is in a cold enough
environment (or the convection efficiency improved by putting it in an
airflow) to ensure the radiator doesn't 'overheat'.

so the heater can't or isnlt cable of truelly dissapating the heat for more than two hours so it turns into a 700W heater

Yes! Thank FECK for that, he's got it!

which for the rest of the day only dissapates 700W of heat have you understood this yet.

Oh no, he hasn't got it yet. ;-( (see above).

A 2KW heater is a 2KW heater for 2 hours then it 'morphes' into a 700W heater

Yes, magic isn't it. Hey, I bet you don't still have a clue why or how
it does that eh?

Why is this difficult to understand, if I want a 700W heater I;d buy a cheaper smaller heater.

But you don't actually have a 700W heater do you? You have told us it
runs for 2 hours at nearly 2kW so if you only had it on for 1 hour you
would have a perfectly good 2kw heater eh?


Cheers, T i m

p.s. What exactly is your skillset Dave?

On Wed, 15 Nov 2017 05:41:26 -0800 (PST), whisky-dave
wrote:

On Wednesday, 15 November 2017 11:55:42 UTC, T i m wrote:
On Wed, 15 Nov 2017 03:30:12 -0800 (PST), whisky-dave


It would depend on where it bridged itself (if it does). It might
already have done that, in which case the measured voltage is even more
worrying!

doesn't worry me in the least because I expected it.

I don't think you can be sure exactly where the voltage drop is coming
from though can (even) you?

No but againn I donlt care.

I'm guessing you do care or this thread wouldn't be as long as it is?

We have those 3 pin sockets in the lab that supply power that are just like those in everyones house, hwo often to yuo worry whether the volatge at that point is 200V or 240V ?

When I bought a heater that was supposed to be 2kW and I got far less
than I expected?

How often to you measure it to check, before vacuuming do you check the voltage before or during vacuuming if not why not ?

I would if the vacuum didn't perform as expected and FWIW, I have a
voltage monitor plugged in all the time.

Next!

Cheers, T i m

On 15/11/2017 11:30, whisky-dave wrote:
On Tuesday, 14 November 2017 16:53:40 UTC, John Rumm wrote:
On 14/11/2017 11:03, Roger Hayter wrote:
John Rumm wrote:

On 13/11/2017 20:38, Roger Hayter wrote:

It seems he already has as much electrical heating as that
autotransformer will ever supply, and is probably exceeding its ratings.
Perhaps someone who knows where it is could have a quick look and see if
any smoke comes out when the voltage drops to 202V?

ISTR that bigclive did a tear-down on one of those voltage reduction
units. At some load point it actually had relays to bridge itself out of
the supply as a self protection mechanism. So you may find enough load
actually takes it out of circuit.

That sounds a sensible arrangement, But doesn't the marked voltage
drop make it a bit unlikely?

It would depend on where it bridged itself (if it does). It might
already have done that, in which case the measured voltage is even more
worrying!

doesn't worry me in the least because I expected it.
That's the advantage of understanding both theory and the real world.

Hmmm Dunning Kruger at work perhaps...

If the wiring is underspecified, that would suggest that close to full
load it is running at over them maximum continuous conductor
temperature rating of the cable. So expect shortened cable life and
elevated fire risk.

If the voltage sags too far, then you get lower PSCC so can expect
slower operation of protective devices under fault conditions, so
increase electrocution risk, and catastrophic cable failure risk.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Wednesday, 15 November 2017 14:37:08 UTC, T i m wrote:
On Wed, 15 Nov 2017 05:38:07 -0800 (PST), whisky-dave
wrote:

On Tuesday, 14 November 2017 18:39:54 UTC, T i m wrote:
On Tue, 14 Nov 2017 09:14:55 -0800 (PST), whisky-dave
wrote:

snip

Aren't you the one who seemed to have no idea about any of this?

No I find out by testing not reading the data sheet.

Because you have it in front of you and don't understand the data
sheet?

I understand some of it.
safety information .

1 / Check that the voltage indicated on the rating plate corresponds with that of the local network before connecting the before connecting the applince to the mains supply.

I don't think they are using the term network correct or not as we use it.

On Wednesday, 15 November 2017 15:25:45 UTC, John Rumm wrote:
On 15/11/2017 11:30, whisky-dave wrote:
On Tuesday, 14 November 2017 16:53:40 UTC, John Rumm wrote:
On 14/11/2017 11:03, Roger Hayter wrote:
John Rumm wrote:

On 13/11/2017 20:38, Roger Hayter wrote:

It seems he already has as much electrical heating as that
autotransformer will ever supply, and is probably exceeding its ratings.
Perhaps someone who knows where it is could have a quick look and see if
any smoke comes out when the voltage drops to 202V?

ISTR that bigclive did a tear-down on one of those voltage reduction
units. At some load point it actually had relays to bridge itself out of
the supply as a self protection mechanism. So you may find enough load
actually takes it out of circuit.

That sounds a sensible arrangement, But doesn't the marked voltage
drop make it a bit unlikely?

It would depend on where it bridged itself (if it does). It might
already have done that, in which case the measured voltage is even more
worrying!

doesn't worry me in the least because I expected it.
That's the advantage of understanding both theory and the real world.

Hmmm Dunning Kruger at work perhaps...

If the wiring is underspecified,

so why did we pay £30K for higher capacity electrics ?


that would suggest that close to full
load it is running at over them maximum continuous conductor
temperature rating of the cable. So expect shortened cable life and
elevated fire risk.

Over the life of teh cable we ran it for about 2 and a bit hours after teh 32A MCB tripped we removed 3 of teh 5 heaters and put 2 on another 32 amp MCB and the final heater on another phase our 'CU" has a 'cut-out rated at 100 AMPS.
I di not think the life of the cable will be significantly shortened because we have 5x 2Kw heaters that spend most of there time at 700W .



If the voltage sags too far, then you get lower PSCC so can expect
slower operation of protective devices under fault conditions, so
increase electrocution risk, and catastrophic cable failure risk.

But not in under 3 hours.

whisky-dave wrote:

John Rumm wrote:

If the voltage sags too far, then you get lower PSCC so can expect
slower operation of protective devices under fault conditions, so
increase electrocution risk, and catastrophic cable failure risk.

But not in under 3 hours.

The 3 hours at 40+ Amps is the "slow" part of the MCB curve, in the
event of a short circuit you want sufficient current to ensure it trips
within the "fast" part of the curve ...

On Wed, 15 Nov 2017 09:00:17 -0800 (PST), whisky-dave
wrote:

snip

They mean (clearly) 'The power distribution network'.

yeah clearly like 220-240V will give you 2KW clearly it doesn't matter what the voltage is or does it.

What do you think? P=VxI

snip

I do I can't take them apart they do NOT belong to me or my department.

I know.

So why do you expect me to take them apart ?

I don't *expect* you to, I suggested you could.

Is that what you do, you get equipemnt from new you think it faulty and you take it about so making the wattenty void ?

It depends on the situation, cost of the equipment, likelihood of
getting satisfaction and all sorts of things. Don't forget, you have
loads of these things are they aren't expensive, even if you had to
pay for one yourself.

I do NOT believe that they have a wiring fault.

I'm not interested in your 'beliefs' mate, just the facts. ;-)

And where will you get them from.....

By asking the supplier or manufacturer or failing any satisfaction
there, myself by taking the panel off.



It has a thermostat, an overtemp switch / cutout and a thermal fuse.

I do NOT know if it has a thermal fuse did you see it mentioned anywhere ?

No, but every similar device I've ever opened has had one and I'm not
sure it would get certification without.

So when would this fuse blow and why isn't it mentioned in the manual ?

When the temperature of the radiator exceeds the setting of the
thermal fuse and it's probably not mentioned because it sometimes
isn't, especially cheap Chinese gear. The reason it's not is because
when it's been activated, the chances are either something has gone
very wrong or the heater has been abused.


These are the actual terms people who know what they are talking about
use to ensure they all understand each other.

https://en.wikipedia.org/wiki/Thermostat
https://en.wikipedia.org/wiki/Therma...Thermal_switch
https://en.wikipedia.org/wiki/Therma...f#Thermal_fuse

None of which appear in the data sheet.

Two of them do, just that you don't understand enough about it all to
realise it. ;-(

No of those do, they use differnt terms.

You are *really* stupid, are trolling, lying or can't read (your
call).

http://www.farnell.com/datasheets/2339828.pdf

P3 "Adjustable Thermostat"
P4 "thermostat knob, thermostat, thermostat, thermostat .."

And if you can't work out that a "overheat protection system" isn't
covered by:

"A thermal switch (sometimes thermal reset or thermal cutout (TCO)) is
a device which normally opens at a high temperature (often with a
faint "plink" sound) and re-closes when the temperature drops. The
thermal switch may be a bimetallic strip, often encased in a tubular
glass bulb to protect it from dust or short circuit. Another common
design uses a bimetallic shallow dome-shaped cap which "clicks" to an
inside-out inverted cap shape when heated, such as the "Klixon" brand
of thermal cutouts. [2]

Unlike a thermal fuse, a thermal switch is usually reusable, and is
therefore suited to protecting against temporary situations which are
common and user-correctable. Thermal switches are used in power
supplies in case of overload, and also as thermostats in some heating
and cooling systems."


The datasheet *you* linked to.

No it says overheat protection system, nothing about thermal cutouts.

See above. " + " = 'pass' in your case in seems.


I know what's happening but I didnlt get that knowledge from the data sheet.

I repeat, you don't know what is happening,

I do.

You haven't proved it yet?


you only report what you
see happening (and are still asking us *why*).

I know why crap underspec heaters.

You know why what?

So if this heater is left on it;s doen;t produce 2KW of heat it doesn't consume 2KW of electrical power it drops to 700W

No, it doesn't consume nor (therefore) give off 2kW of heat because
the supply voltage won't allow it to.

The supply will allow it, the supply has little to nothing to do with it, it is plugged into the mains supply.

Aw bless ... it's like trying to explain it all to a child. ;-)

It IS NOT the supply that is reducing the power consumption from teh stated 2KW to 700W.

I never said it was and that fact that you have suggested I have just
about says it all.

Perhaps you're getting the overheat protection system mixed up with ohms law.

Aww, bless.

snip

Can you just have the NoII element on without
the NoI .

Yes.


and if so, I wonder if it would then still cycle on the
overtemp stat?

No idea, I would expect it to cycle a little.

Expect, why don't you try it?

But there's no cycling at 700W

Under the current conditions, no.


Don;t forget the data sheep spoec that says any voltage from 220-240 the rad will comsume 2KW ;-P

The good news is at least you (now seem to) realise that is
impossible. ;-)

New it along alone although I didn't consider it particually important for our use.

What?


What would you expect a heater with a label that says 220-240 50Hz 2000W to do ?

Consume circa 2000W at 240V and,

and yet at 212V it's consuming just 700W.

And?



if the surface area isn't big enough
to dissipate all that energy, get overly hot and trip out on it's
overtemp stat, even when the main stat is still calling for heat.

Yes my one at home claims to have a larger surface area and has coluumns for the heat to rise rather than 'hang about' but then it was about £130 (£160 now) compared to just £25.

The cost shouldn't have anything to do with it other than a lower
powered heating element would probably be cheaper and be less likely
to cause the rad to overtemp under typical conditions.


However, I think I would expect it to cut out entirely, not back to
the low power element.

That's what I would have assumed, but only if it got dangerously hot or someone covered the heater with something, I wouldnlt expect such a heater just to cut out or even reduce 'power'.

Agreed.

Do you expect your 450W to reduce to 126W after about 2 hours of being on ?

Nope. However, mine cuts down from 450 to 0W in much less time than 2
hours (even though the main stat temp hasn't been reached).

If not way not.

Because it's a single element heater so one can't 'cut out' and
therefore change the total wattage.



Yep pretty much says that in the manual and I've tried it and it works
it goes dwon to 0W consumtion when laying on it's side or rather it switchees out at about 40 degrees.

Yes, you said. If not a physical button underneath, it would often be
a ball, cup and micro switch arrangement.

Yep I know, I doubt and can't find a physical button this would be difficult to implemete on a heater with casters. I have that form of cut out on my fan heater.

Ok.


which acutally does cut out or off the electicity supply to the heater giving a reading of 0 Watts.

Yes, that is *another* safety function and only relevant to the
discussion if you knock the heater over. It cuts the power to 0, just
as the main thermostat does.

Yes I know, I've know that all along. I've had one in my office for about 2 years now.

You said 'The cut-out is the Safety tip over switch'. No one was
talking about such things (but you). I was talking of the 'overtemp
safety cutout'. You got confused.

No you were the one that got confused a cut out cuts off so there is NO overtemp cut out, because it doesnlt cut out, power remains the LEDS REMAIN ON.

What?

So it canlt be cutting out the power can it.

All the 'cut outs' cut the power, what would be the point otherwise.

The cut out is for when it tips over, as the LEDs go out they flicker too so it;s not a micro switch either, so likely a mercury or non-mercury tilt switch

Ah, like one with a ball, cup and micro switch possibly?

which does cut out the power, unlike the overheat protection which keeps the power connected.

It does not keep the power connected to the heater element does it
(which is all it needs to do for that safety feature).

snip

Yes (FFS), the overtemp switch, *not* the overtemp fuse. Really, is
this all that difficult for you?

There is NO overtemp fuse,

Ah, so you have xray vision now? Have you swapped that for common
sense and reason perchance?

it's probbly a bimetalic switch iven the price point.

What, they would fit something more expensive *and* more dangerous
because of the manufacturing cost?

It's NOT a cut out its NOT a fuse.

Of course it isn't, if you say so.


so the only sure way of getting the heater to again comnsume 2KW is to use a cold air blower (I have another fan heater) to blow cool air over the fins of the 2KW heater.

Yup, because as I explained elsewhere, the radiator is unable to
dissipate sufficient heat fast enough and so 'overheats' and trips
itself (or the just main element in your case it seems) out.

Yes trips out and auto-resets yes.

Yes, because it's an 'overtemp stat', not an 'overtemp fuse'.

It's not a fuse well done. A fuse would need to be replaced.

Mate, you are either *sooo* desperate to prove that you think you have
even the slightest grasp on this that you will try anything, no matter
how stupid it makes you look or you *really* have comprehension issues
(or are on a wind up).

For you to even stat to be able to counter me on any of this you would
have to keep track of it all and it is obvious that you can't.

Print any of it off and take to an adult and get them to tell you who
seems to have any idea what they are talking about (and I mean
*anyone* who has tried to help you here, not just me).


And while in this state it does NOT give out 2KW of heat.

No, really, why didn't you say earlier? Hey, I wonder why it doesn't
... ?

I did but you must have ignored it.

Whoosh.


Are you now just trolling mate?

All I'm saying is a 2KW heater won't consume 2KW if yuo leave it on 'full' power

It will if on a suitably rated supply and does initially.

It's always been on a suitabley rated supply.

Not for 2kW output it hasn't.

It's within the specified range.

Really?.




and does initially.

So the penny has started to drop at long last.

Nope, obviously it hasn't (with you). ;-(

How can you be so thick ?

Bless.



it will drop to 700W

So must have been higher (than 700W) or it wouldn't 'drop' would it?

well done you're almost there now.

Bless.

Nah that's for the religous.

Hey, you were the one with all the beliefs. I *know*.


Nothing to do with the thermostat (the thinbg with the knob on it) that remains at maxium setting .

Where did I mention anything about the thermostat affecting your
results? What part of 'indefinitely *until* the temperature set by the
thermostat is met' don't you get?

Clue, AFAIK, the temperature set by the main stat has *never* been met
yet.

I know, but I;ve no idea what that temerature might be do you ?

Yes, 'Maximum'. Other than that, the fact it hasn't been met is all we
need to know.

Because threr arenl;t any temperature markings like you get on typical central heating systems why do you think that is ?

I don't 'think' why that is, I know ... because the thermostat isn't
calibrated or very accurate (now you know as well!). ;-)




So, I was going to design and build a controller that uses an Arduino
Nano, a triac and a couple of external temperature sensors to properly
'manage' the heater. The std heater plugs into my solution.

Are you suggeting that the thermostats on those heaters don't work ?

Nope.

So what's wrong with the heaters then ?

Nothing. Everything is fine ... (obviously).



Temp sensor 1 will be clipped to the heater and will moderate the max
temp of the rad to less than the internal overtemp switch.

why bother.

To make it suitable for a bedroom.

Are you saying these heaters arenlt suitable for bedrooms ?

Yes, because of the noise levels.

Where did you read that in the manaul ?

There was no mention of sound levels in the manual.

Or perhaps yuor getting confused where it says it;'s OK for use with children over the age of 8. Although I have no idea where they get that cut-off from ;-P

Nope ... I thought those limits may well apply to you though.



You see most people buying these heaters arent; likey to set up an arduino

I know, especially you eh! ;-)

I certainly wouldn't buy a cheap £25 heater then spend more on a device to control it.

And I'm not? Maybe the people who sold you the autotransformer also
supply you Arduinos?



The *reason* for doing that is we only need a small heater in the
bedroom but both the overtemp stat and thermostat are quite noisy,
hence the electronic solution.

well noise isn't our concern the amount of heat supplied is more important.

No! Why didn't you say that at the beginning! ;-(

You really think a few clicks of a radiator will wake up the or so students in the lab. about 25 students at the moment.

Whoosh

Here's a link to what the lab was like do you really think a radiator click will do anything.

https://www.youtube.com/watch?v=JCBXuXBAl4g

Whoosh.


So what made you choose 450W heater ?

Because it was tiny (in size, just so you don't confuse small size
with low power).

How tiny I've had a 7805 on a TO220 heatsink reach 101C, hotter than my raidiator gets at 98C. So I can devise an even smaller heater than you have brought.

Good for you.

Doing the calculations should be step one mate, not step two.

Shouldn't be a step for me or anyone else here.

That's *exactly* who should be doing it. Or do you think CPC should do
it for you, or someone here?

It wasn't for you ?

Yes, it was.

in your own home ?,

Yes.

size was the proity for you.

Yes, because I knew that even that small would heat the room
sufficiently. You knew no such thing with the rads that were bought
for the lab (and still don't).


When we asked for heating or we'd leave the building because it was below the minium temerature and therfore the labs wouldn't run and the students would complain, they ordered 40 convections heaters for use and brought over 8 old ones as a stop-gap measure, some had broken feet and wouldn't stand up properly.

Ok ... ?

About 9 years ago we were banned from using convection heaters in labs, a few years later they banned them from labs and offices unless fixed to a wall, a year later they banned them completely due to H&S concerns.

Ok ... ?

I found it a little odd that estates, those in charge of buildings, services and maintaince didn't get this email/memo or directive.

Sounds par for the course there ...

When we told them we can't use them they cancelled the order and ordered oil filled rads which we asked for as we can use those, they didnl;t ask which ones or what type like you went for size I assume they went for cheapness,

Ok.

Only problem with them is that the mains leads aren't really long enough for what we wanted.

Ok.


Can you show yuor calculations for step 1 ?

I don't need to because the heater is more than capable of meeting the
requirements.

Poor excuse,

No excuse, fact mate.

how did you know it'd be cable of meeting the requirements.

Because I'd had an even lower wattage heater in there previously (as
used in a caravan etc).


snip

Well, one precludes the other (doh). eg (For the hard of thinking), if
it was designed to work like that it could still be a design fault but
then wouldn't be a production wiring fault.

So there's nothing wrong with them legally is there,

If you know, why are you asking me?

so no reason they can't be sold.

I don't know if the regs allow for only one element be cut out in the
event of an overheat situation?



perhaps a casual users understanding like those that ordered them who have degrees in managment but can't tell a plug from a socket.

Or determine the energy requirements of a space (and why you would
need to) or how a basic electric radiator works?

Then how would you go about such a thing ?

See the repli(es) from John Rumm.

or rather what sort of figure would you end up with ?

The energy required to attain a desired temperature assuming the worst
(realistic) case temperature outside.



And if it did you would contact the supplier and ask why eh?

That would depend on the car and the cost of that car.

Irrelevant.

Very relivant a 2CV has a 0-60 time but try getting it to pull a caravan.

We were talking trailers ... and I tow one behind my solo cycle and
behind my 200cc Messerschmitt KR200. However, it's still irrelevant as
you have no idea how much each trailer weighed.


I know you don't, in spite of me explaining it several times and
suggesting you check one yourself (wiring) and contact the supplier /
manufacturer.

Not interested when 3 of the 5 all do the same just like it says in the supplied manual.

Where does it explain in the manual that the over temp stay only works
on the bigger element?

It doesn't mention how it regualtes over temerature and more than it describes the tilt cut out.

Quite. So you are happy to assume because 3 out of 5 do the same
thing, there can't be any issues.

snip

By measuring their duty cycle at a range of (ambient) temperatures and
taking it from there.

How would you do that without first buying one ?

You can't?

Where does it mention a duty cycle, it does so why assume one.

It doesn't and because you have learned that there is. I have assumed
nothing.



Explain it to me, if you do really understand this.

See above (and there is no *if*).

there;s a really big if, you claim to be able to calculate what you need and then using that information you'd buy the correct rad.

You could if you asked the right questions. Like, 'does this heater
give 2kW continuously under std conditions'.



I would NOT be happy buying a 2KW heater just to reduce it to 1KW with a diode in the hope it didn't drop to 700W.

I'm not saying you would be happy to do that ... I was just trying to
help you understand the problem.

I know the problem crap heaters, or rather heatrs that donl;t do what they imply.

They do do what they imply, but not for the length of time you guessed
they might. ;-)




The thermostat is meant to control both the amount of current heating the eliment and therfore the amount of heat generated or whay donlt yuo explain what the thermostat is for.

Because at the moment, the main thermostat hasn't come into it as the
room hasn't reached the required temperature.

When will it reach the required temperature ?

Who knows if it ever will as you haven't done the thermal calcs.

That is the main point.

It is, as we have been saying all along.

No point in buying 2KW heaters that go down to 700W after two hours.

That may well be true, but you would have to check against the calcs.
If the average output of the rads is sufficient they could be
perfectly ok.

If I buy a 2KW heater I expect to get 2KW for as long as it is on.

Agreed, you *might*, if you were aware there were some out there that
couldn't manage that.

I'd expect the fins/metal and machnicas to be able to copy with being on for days at 2KW, if the heater is rated at 2KW.

I'd agree, and there are that can do that, but probably not for that
money or size.


If yuo look in ther manual it tells you how to set these units up using the thermostat rather than the over heat protection or the trip out.

No, does it rolls eyes, I wonder why no one picked up on that
sooner?

yuo certainly think a 2KW heater should run at just 700W.

Whoosh ..

I expect it to run at 2KW .

We know.




So how woul yuo work that out if 2KW heaters all reduce to 700W after 2 hours ?

Whoosh ...

answer the question.

Really? You measure the power consumed over a long enough period to
calculate the average.


This is the key point the point you keep missing.

I am missing nothing here mate, only the fact that you are just
trolling?

you;re the one trolling here,

What did the adult say when you showed them the printout?

why canl;t you understand that a 2KW heater is meant to give you 2KW worth of heat UNLESS it;s reached thermost temp. set

What can't you understand that I fully understand that (and always
have).

If not it should carry on at 2KW not give up and go down to 700W.

Maybe it would if you put it in somewhere cold or draughty enough?

Why can;t yuo understand such a simple thing.

What do you *actually* think I (or anyone who has tried to help you)
doesn't understand about any of this mate? I can assure you that
everything everyone has said on the matter makes perfect sense ... the
only one who seems to be floundering about like a fish out of water is
you?

What you have been given many times over is the answer to all your
questions. We can't make you understand them.

Cheers, T i m

On 15/11/2017 17:17, whisky-dave wrote:
On Wednesday, 15 November 2017 15:25:45 UTC, John Rumm wrote:
On 15/11/2017 11:30, whisky-dave wrote:
On Tuesday, 14 November 2017 16:53:40 UTC, John Rumm wrote:
On 14/11/2017 11:03, Roger Hayter wrote:
John Rumm wrote:

On 13/11/2017 20:38, Roger Hayter wrote:

It seems he already has as much electrical heating as that
autotransformer will ever supply, and is probably exceeding its ratings.
Perhaps someone who knows where it is could have a quick look and see if
any smoke comes out when the voltage drops to 202V?

ISTR that bigclive did a tear-down on one of those voltage reduction
units. At some load point it actually had relays to bridge itself out of
the supply as a self protection mechanism. So you may find enough load
actually takes it out of circuit.

That sounds a sensible arrangement, But doesn't the marked voltage
drop make it a bit unlikely?

It would depend on where it bridged itself (if it does). It might
already have done that, in which case the measured voltage is even more
worrying!

doesn't worry me in the least because I expected it.
That's the advantage of understanding both theory and the real world.

Hmmm Dunning Kruger at work perhaps...

If the wiring is underspecified,

so why did we pay £30K for higher capacity electrics ?


that would suggest that close to full
load it is running at over them maximum continuous conductor
temperature rating of the cable. So expect shortened cable life and
elevated fire risk.

Over the life of teh cable we ran it for about 2 and a bit hours after teh 32A MCB tripped we removed 3 of teh 5 heaters and put 2 on another 32 amp MCB and the final heater on another phase our 'CU" has a 'cut-out rated at 100 AMPS.
I di not think the life of the cable will be significantly shortened because we have 5x 2Kw heaters that spend most of there time at 700W .

I am assuming you did not have a rewire done just prior to running this
experiment?

If this experiment *has* demonstrated that the installation was sub
standard, then it has likely been that way for some time.

If the voltage sags too far, then you get lower PSCC so can expect
slower operation of protective devices under fault conditions, so
increase electrocution risk, and catastrophic cable failure risk.

But not in under 3 hours.

It was not the 3 hours that would bother me. Especially if anyone is
considering running with this daft idea for any extended period.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 15/11/2017 17:28, Andy Burns wrote:
whisky-dave wrote:

John Rumm wrote:

If the voltage sags too far, then you get lower PSCC so can expect
slower operation of protective devices under fault conditions, so
increase electrocution risk, and catastrophic cable failure risk.

But not in under 3 hours.

The 3 hours at 40+ Amps is the "slow" part of the MCB curve, in the
event of a short circuit you want sufficient current to ensure it trips
within the "fast" part of the curve ...

Indeed...

You need 160A to make sure a B type MCB will trip in the magnetic part
of its response curve and that implies a maximum loop impedance at the
point of the fault of 230 / 160 = 1.44 ohms [1]

Even if the circuit is in spec and meets that requirement at all
sockets, running at only 202 volt gives a reduced potential worst case
PSSC of 202 / 1.44 = 140A, which could leave you on the thermal portion
of the response curve and *20 seconds* away from disconnection. (and
that ignores the effect of elevated conductor temperature on the loop
impedance)



[1] I am assuming that the wiring was done before 17th edition amendment
3 and the 5% reduction in Cmin.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Wednesday, 15 November 2017 17:28:28 UTC, Andy Burns wrote:
whisky-dave wrote:

John Rumm wrote:

If the voltage sags too far, then you get lower PSCC so can expect
slower operation of protective devices under fault conditions, so
increase electrocution risk, and catastrophic cable failure risk.

But not in under 3 hours.

The 3 hours at 40+ Amps

what makes you think it's 40 amps + ?

whisky-dave wrote:

Andy Burns wrote:

The 3 hours at 40+ Amps

what makes you think it's 40 amps + ?

I thought that's where we started weeks ago, that you expected to be
able to trip a 32A breaker with the heaters, and I gave you the 2.7
hours figure?

As John has calculated, if the supply is so "soft" that it drops to
202V, it might only be able to supply 140A, so a short circuit could
last long enough to cause serious damage ...

On Wednesday, 15 November 2017 19:44:09 UTC, T i m wrote:
On Wed, 15 Nov 2017 09:00:17 -0800 (PST), whisky-dave
wrote:

snip

They mean (clearly) 'The power distribution network'.

yeah clearly like 220-240V will give you 2KW clearly it doesn't matter what the voltage is or does it.

What do you think? P=VxI

Yep so 220V wouldn;t give the same power output as 240V would it but according to the label any voltage from 220 to 240 will give 2000W not about 2KW not 2001 not 2002 ....


I do I can't take them apart they do NOT belong to me or my department.

whisky-dave wrote:

On Wednesday, 15 November 2017 19:44:09 UTC, T i m wrote:
On Wed, 15 Nov 2017 09:00:17 -0800 (PST), whisky-dave
wrote:

snip

They mean (clearly) 'The power distribution network'.

yeah clearly like 220-240V will give you 2KW clearly it doesn't matter
what the voltage is or does it.

What do you think? P=VxI

Yep so 220V wouldn;t give the same power output as 240V would it but
according to the label any voltage from 220 to 240 will give 2000W not
about 2KW not 2001 not 2002 ....

snip

I think that has to be regarded as a 'rating' rather than an electrical
function statement. In reality the 2kW will be at a particular
voltage, usually 240V in the case of electric showers which have a
similar rating system. One can then be pretty certain that the power
output will be about 1700W at 220V. (Mental arithmetic plus binomial
theorem rather then precision calculation.)

BTW, I am quite sure they would not claim the 2kW was precise to the
nearest watt at any voltage. +/- 5% would be a reasonable achievement,
say 1.9 to 2.1kW. Or it could be a maximum, then 1.8 to 2.0kW. In the
latter case the 220V power might be as low as 1500W




--

Roger Hayter

On Thursday, 16 November 2017 14:22:01 UTC, Andy Burns wrote:
whisky-dave wrote:

Andy Burns wrote:

The 3 hours at 40+ Amps

what makes you think it's 40 amps + ?

I thought that's where we started weeks ago, that you expected to be
able to trip a 32A breaker with the heaters, and I gave you the 2.7
hours figure?

what makes yuo think it;s 40 amps will you answer this or not.


As John has calculated, if the supply is so "soft" that it drops to
202V, it might only be able to supply 140A, so a short circuit could
last long enough to cause serious damage ...

only 140 amps where or how did you get that figure ?

On Thursday, 16 November 2017 20:05:21 UTC, Roger Hayter wrote:
whisky-dave wrote:

On Wednesday, 15 November 2017 19:44:09 UTC, T i m wrote:
On Wed, 15 Nov 2017 09:00:17 -0800 (PST), whisky-dave
wrote:

snip

They mean (clearly) 'The power distribution network'.

yeah clearly like 220-240V will give you 2KW clearly it doesn't matter
what the voltage is or does it.

What do you think? P=VxI

Yep so 220V wouldn;t give the same power output as 240V would it but
according to the label any voltage from 220 to 240 will give 2000W not
about 2KW not 2001 not 2002 ....

snip

I think that has to be regarded as a 'rating' rather than an electrical
function statement.

Personally I think it;s a maxium rating if used withint that voltage range also not that they specify the frequency while that isnlt expected to change I'm not sure what would happen if at 220V the frequency double or halved.

In reality the 2kW will be at a particular
voltage, usually 240V in the case of electric showers which have a
similar rating system.

Because 240V is the maxuim continous voltage suplied by the gird to households.

One can then be pretty certain that the power
output will be about 1700W at 220V. (Mental arithmetic plus binomial
theorem rather then precision calculation.)

Yep I agree that's why I wasn;t bother bother with teh 1.7KW result I got.
With 5 heaters on the same circiut I was getting about 1.6KW which again I wasn't concerned about.


BTW, I am quite sure they would not claim the 2kW was precise to the
nearest watt at any voltage. +/- 5% would be a reasonable achievement,
say 1.9 to 2.1kW. Or it could be a maximum, then 1.8 to 2.0kW. In the
latter case the 220V power might be as low as 1500W

So I was suprised to find that I was getting just 700W from a full on 2KW heater.

On Thursday, 16 November 2017 08:58:00 UTC, John Rumm wrote:
On 15/11/2017 17:28, Andy Burns wrote:
whisky-dave wrote:

John Rumm wrote:

If the voltage sags too far, then you get lower PSCC so can expect
slower operation of protective devices under fault conditions, so
increase electrocution risk, and catastrophic cable failure risk.

But not in under 3 hours.

The 3 hours at 40+ Amps is the "slow" part of the MCB curve, in the
event of a short circuit you want sufficient current to ensure it trips
within the "fast" part of the curve ...

Indeed...

You need 160A to make sure a B type MCB will trip in the magnetic part
of its response curve and that implies a maximum loop impedance at the
point of the fault of 230 / 160 = 1.44 ohms [1]

So why did it trip out ?


Even if the circuit is in spec and meets that requirement at all
sockets, running at only 202 volt gives a reduced potential worst case
PSSC of 202 / 1.44 = 140A, which could leave you on the thermal portion
of the response curve and *20 seconds* away from disconnection. (and
that ignores the effect of elevated conductor temperature on the loop
impedance)

140A I don't think we were drawing anywhere near that. Is that the sort of current you expect from 5 2KW heaters running on 202V and a soldering re-work station of about 160W max. ?


[1] I am assuming that the wiring was done before 17th edition amendment
3 and the 5% reduction in Cmin.

I'm not sure that is relevant to this.

On Wednesday, 15 November 2017 15:12:17 UTC, T i m wrote:
On Wed, 15 Nov 2017 05:41:26 -0800 (PST), whisky-dave
wrote:

On Wednesday, 15 November 2017 11:55:42 UTC, T i m wrote:
On Wed, 15 Nov 2017 03:30:12 -0800 (PST), whisky-dave


It would depend on where it bridged itself (if it does). It might
already have done that, in which case the measured voltage is even more
worrying!

doesn't worry me in the least because I expected it.

I don't think you can be sure exactly where the voltage drop is coming
from though can (even) you?

No but againn I donlt care.

I'm guessing you do care or this thread wouldn't be as long as it is?

It's not me that's making the thread long.

Mine was a simple question regarding what power would yuo expect a 2KW heater to use. I wanslt expecting pin point accuracy when I knew the jeaters specs was 2KW 220-240V there;s a 10% change without the power altering.

Not sure about you but if I put the heater on a 220V supply I'd expect it to consumer a bit less power than it would on a 240V supply.
Taking it up to 260V would be beyond it's quoted spec. and I;d assume that the power would increase until a cut-out tripped out protecting the elemants and the heater in gerneral.





We have those 3 pin sockets in the lab that supply power that are just like those in everyones house, hwo often to yuo worry whether the volatge at that point is 200V or 240V ?

When I bought a heater that was supposed to be 2kW and I got far less
than I expected?

Did yuo take it back or report it as faulty ?


How often to you measure it to check, before vacuuming do you check the voltage before or during vacuuming if not why not ?

I would if the vacuum didn't perform as expected and FWIW, I have a
voltage monitor plugged in all the time.

Next!

Cheers, T i m