On Thu, 9 Nov 2017 08:15:34 -0800 (PST), whisky-dave
wrote:

On Thursday, 9 November 2017 15:18:45 UTC, T i m wrote:
On Thu, 9 Nov 2017 07:12:04 -0800 (PST), whisky-dave
wrote:

snip

So are you asking why it's currently showing ~700 W or why it's
fluctuating around 700W

Yes why is a 2KW heater only drawing 700W when fully on, if it was up to temperatury I'd expect it to disconneced with a bimetalic strip or something more advanced and would be 0W not 700W.

As would I ... so it sounds like the 700W element is in all the time?


Except if you turn the knob thermostate down (anti-clockwise)then it switches off to 0W and the LEDs go out.

Sounds like it's the upper limit stat that is cutting in and out on
the bigger element (only) ... before the main stat cuts everything
out? Do you have a IR thermometer? If so it might be interesting to
see what surface temperatures these clicks and measurements apply to.

If they are keeping them I'd be inclined to open one up and make a
wiring diagram (or see if there is one in there or in the manual).

Cheers, T i m

"whisky-dave" wrote in message
...
On Thursday, 9 November 2017 15:16:51 UTC, Andy Burns wrote:
whisky-dave wrote:

Yes well the first idea was 40 convector heaters were ordered but we
had to inform those that ordered them that the college had banned
them for use in labs and offices.

Has someone stolen the college's boiler?

It was knocked down and the area is now the New £50M graduate centre.

http://www.qmul.ac.uk/media/news/items/198330.html

Bet they kept you chained up out the back when the royals showed up.

On 09/11/2017 14:01, Harry Bloomfield wrote:
pamela presented the following explanation :
I thought it was 13A because that is the max rating for an plugged in
appliance.

So does that means I could safely run two 10A appliances from the
same wall outlet?

From a twin socket outlet, yes.

However if they were to run for an extended period the socket would fail.

--
Adam

On 08/11/2017 22:24, Tim Watts wrote:

3) If you overload a cable to say twice its rating and the MCB takes say
Â*15-20 minutes to trip, the cable has not instantlo y heated up to
beyond 70C - it's gradually overheating and the Type B curve is designed
to reflect that.

It's nothing to do with the B curve:-)

The same applies to C and D MCBs


--
Adam

On 09/11/2017 18:54, ARW wrote:
On 09/11/2017 14:01, Harry Bloomfield wrote:
pamela presented the following explanation :
I thought it was 13A because that is the max rating for an plugged in
appliance.

So does that means I could safely run two 10A appliances from the
same wall outlet?

*From a twin socket outlet, yes.

However if they were to run for an extended period the socket would fail.

Would they?

I remember from my first job (a temporary one CADding up the packaging
drawings and datasheets for the Volex 9000 range) that the twin sockets
were rated at 29A.

If I remember, I'll ask my dad at the weekend - as he used used to run
the drawing office and the test lab there. The test lab was full of
plugs and sockets being run continuously, plugged in and out repeatedly
or swiched on and off endlessly - all in heated boxes to accelerate ageing.

SteveW

On 09/11/2017 19:03, Steve Walker wrote:
On 09/11/2017 18:54, ARW wrote:
On 09/11/2017 14:01, Harry Bloomfield wrote:
pamela presented the following explanation :
I thought it was 13A because that is the max rating for an plugged in
appliance.

So does that means I could safely run two 10A appliances from the
same wall outlet?

*From a twin socket outlet, yes.

However if they were to run for an extended period the socket would fail.

Would they?

I remember from my first job (a temporary one CADding up the packaging
drawings and datasheets for the Volex 9000 range) that the twin sockets
were rated at 29A.

If I remember, I'll ask my dad at the weekend - as he used used to run
the drawing office and the test lab there. The test lab was full of
plugs and sockets being run continuously, plugged in and out repeatedly
or swiched on and off endlessly - all in heated boxes to accelerate ageing.

Well I don't have the web page to hand, but I am sure it was shown a
double socket failed at 19.5A after an hour or so.

I'll be delighted if you can get some old Volex info.


--
Adam

In article ,
ARW wrote:
On 09/11/2017 14:01, Harry Bloomfield wrote:
pamela presented the following explanation :
I thought it was 13A because that is the max rating for an plugged in
appliance.

So does that means I could safely run two 10A appliances from the
same wall outlet?

From a twin socket outlet, yes.

However if they were to run for an extended period the socket would fail.

What is the theory behind a double socket not being able to take 26 amps
total? The actual sockets and switches and terminals are identical to a
one gang of the same make - which only leaves the bus bars between them.

--
*Indian Driver - Smoke signals only*

Dave Plowman London SW
To e-mail, change noise into sound.

On 10/11/2017 00:28, Dave Plowman (News) wrote:

What is the theory behind a double socket not being able to take 26 amps
total? The actual sockets and switches and terminals are identical to a
one gang of the same make - which only leaves the bus bars between them.

I think it stems from the way BS1363 specified the test for temperature
rise. In a single socket that was with a 14A load. In a double socket
it was 14A and 6A loads. That was still true in BS1363-2:1995 but I've
not checked the current currents.





--
Robin
reply-to address is (intended to be) valid

Robin wrote:

In a single socket that was with a 14A load. In a double socket
it was 14A and 6A loads. That was still true in BS1363-2:1995 but I've
not checked the current currents.

Still the same for 2016 edition.

It does mention 2x 14A for unfused outlets with more than 2 sockets, but
any trailing multi-way, or wall mounted outlet I've ever seen with more
than 2 sockets has been fused.

In article , Dave Plowman (News)
wrote:
In article , ARW
wrote:
On 09/11/2017 14:01, Harry Bloomfield wrote:
pamela presented the following explanation :
I thought it was 13A because that is the max rating for an plugged
in appliance.

So does that means I could safely run two 10A appliances from the
same wall outlet?

From a twin socket outlet, yes.

However if they were to run for an extended period the socket would
fail.

What is the theory behind a double socket not being able to take 26 amps
total? The actual sockets and switches and terminals are identical to a
one gang of the same make - which only leaves the bus bars between them.

cost cutting?

--
from KT24 in Surrey, England

Andy Burns wrote:

any trailing multi-way, or wall mounted outlet I've ever seen with more
than 2 sockets has been fused.

B&Q sell a 3-way that's apparently unfused

http://www.diy.com/departments/holder-13a-white-switched-socket/262292_BQ.prd

On Thursday, 9 November 2017 16:41:43 UTC, T i m wrote:
On Thu, 9 Nov 2017 08:15:34 -0800 (PST), whisky-dave
wrote:

On Thursday, 9 November 2017 15:18:45 UTC, T i m wrote:
On Thu, 9 Nov 2017 07:12:04 -0800 (PST), whisky-dave
wrote:

snip

So are you asking why it's currently showing ~700 W or why it's
fluctuating around 700W

Yes why is a 2KW heater only drawing 700W when fully on, if it was up to temperatury I'd expect it to disconneced with a bimetalic strip or something more advanced and would be 0W not 700W.

As would I ... so it sounds like the 700W element is in all the time?


Except if you turn the knob thermostate down (anti-clockwise)then it switches off to 0W and the LEDs go out.

Sounds like it's the upper limit stat that is cutting in and out on
the bigger element (only) ... before the main stat cuts everything
out? Do you have a IR thermometer? If so it might be interesting to
see what surface temperatures these clicks and measurements apply to.

We do have an IR thermo... good idea, providing I can find it.

What temperature would you expect say the half way up the fin should be.
I know it's to hot to hold on to as I tried.


If they are keeping them I'd be inclined to open one up and make a
wiring diagram (or see if there is one in there or in the manual).

The manual is on line and has the same details as the one supplied in the box.
When you say 'they' it is the estates department I doubt they'd like me taking their new stuff apart and I don't particually want to.
I have an oil filled radiator at home that works as I'd expect it to, but then that one was over £100 rather than £35.



Cheers, T i m

On 09/11/2017 15:12, whisky-dave wrote:
On Thursday, 9 November 2017 14:54:23 UTC, T i m wrote:

So are you asking why it's currently showing ~700 W or why it's
fluctuating around 700W

Yes why is a 2KW heater only drawing 700W when fully on, if it was up
to temperatury I'd expect it to disconneced with a bimetalic strip or
something more advanced and would be 0W not 700W.

It would suggest it is not "fully on". It might be that the stat does
not fully disconnect both elements - perhaps just the 1300W one. If that
were the case it would cycle between ~2kW and 700W during normal operation.

Note also that some heaters are configurable. I found some wall mounted
2kW fan heaters I ordered a while back actually ran at a default max of
1kW unless you set an internal switch to allow the full 2kW.


--
Cheers,

John.

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

On Fri, 10 Nov 2017 18:18:52 +0000, John Rumm
wrote:

n.

On Fri, 10 Nov 2017 04:31:50 -0800 (PST), whisky-dave
wrote:

snip

Sounds like it's the upper limit stat that is cutting in and out on
the bigger element (only) ... before the main stat cuts everything
out? Do you have a IR thermometer? If so it might be interesting to
see what surface temperatures these clicks and measurements apply to.

We do have an IR thermo... good idea, providing I can find it.

;-)

What temperature would you expect say the half way up the fin should be.
I know it's to hot to hold on to as I tried.

I can't say for your rad but when I was experimenting with mine I
think it was pretty high ... as I think the thermal trip was set at
110 DegC or summat (but that may be wrong).

So, if you hear something click and the wattage from 2000 to 700, but
turning the main stat down sees the current drop to zero, the thought
is that the upper limit stat is cutting the power to the main element
(because the rad is overheating itself) before the main (room-ish)
temp stat is cutting the power to it all?

So, with the IR thermometer looking say midway up the rad, and you
monitoring the power drawn, see if you can work out a pattern between
the clicks, lights and temperature.

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'.

If you turn the stat down to just above the current temperature, you
may find that (the main stat) will cut out (0W) before the overtemp
stat (leaving 700W).


If they are keeping them I'd be inclined to open one up and make a
wiring diagram (or see if there is one in there or in the manual).

The manual is on line and has the same details as the one supplied in the box.

Ok.

When you say 'they' it is the estates department I doubt they'd like me taking their new stuff apart and I don't particually want to.

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

I have an oil filled radiator at home that works as I'd expect it to, but then that one was over £100 rather than £35.

Shouldn't make any difference what it cost to how it works.

Cheers, T i m

On Fri, 10 Nov 2017 18:41:03 +0000, wrote:

On Fri, 10 Nov 2017 18:18:52 +0000, John Rumm
wrote:

n.

Note also that some heaters are configurable. I found some wall mounted
2kW fan heaters I ordered a while back actually ran at a default max of
1kW unless you set an internal switch to allow the full 2kW.

The ones like that I once looked after had the internal switch as a
rocker switch. A couple of small 2mm holes drilled opposite the switch
ends let me change them by using a small knitting needle poked through
the holes in a simlar manner to the way many battery powered amber
road works warning lamps used to be switched on/off using a matchstick
poked through a hole.

That could explain why dave only reads a max of ~1700W (1000 + 700W)
but I'm not sure how you would manage the 1300W down to 1000 (other
than the low voltage supply he mentioned).

I think it's just wired incorrectly or strangely, with the 700W
element not protected by the overtemp stat (because it alone would be
unlikely to take the rad to overtemp and said stat couldn't handle the
full ~200W)? shrug.

I assume there is still a thermal fuse in there providing the ultimate
overtemp protection?

Cheers, T i m

On 09/11/2017 14:54, Andy Burns wrote:
Johnny B Good wrote:

Starting a sentence with "So" is a totally unnecessary and annoying
affectation.
So what?

See, it does change the meaning sometimes ...

So it does.

--
Adam

On 08/11/2017 12:25, whisky-dave wrote:

As some might have read we've been supplied with a number of oil filled radaitors

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

So I unpacked them and installed them, one by one.

In an attempted to trip our 32 amp circuit braker I would have thought that 5 would have done it, but they didn't.

On switch on they started at about 1.6KW (using an old maplin power meter)
I left them fully on, that's the highest setting .

The lab voltage dropped from the 220V to about 202V so that accounts for it I guess.

But what realy suprised me was the power consumption of a radiator when it was full on, anyone care to guess what it was.

Voltage 202


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


--
Adam

On 09/11/2017 16:15, Johnny B Good wrote:
On Thu, 09 Nov 2017 14:54:48 +0000, Andy Burns wrote:

Johnny B Good wrote:

Starting a sentence with "So" is a totally unnecessary and annoying
affectation.
So what?

See, it does change the meaning sometimes ...

That may be the only example of valid usage. There may be other valid
usage cases but I can't think of any right now so I'll leave it to others
to provide additional examples if they care enough to make the effort.

So that it is clear for everyone, give an example.

(see what I did there?)


--
Cheers,

John.

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

On Sat, 11 Nov 2017 18:04:48 +0000, John Rumm wrote:

On 09/11/2017 16:15, Johnny B Good wrote:
On Thu, 09 Nov 2017 14:54:48 +0000, Andy Burns wrote:

Johnny B Good wrote:

Starting a sentence with "So" is a totally unnecessary and annoying
affectation.
So what?

See, it does change the meaning sometimes ...

That may be the only example of valid usage. There may be other valid
usage cases but I can't think of any right now so I'll leave it to
others to provide additional examples if they care enough to make the
effort.

So that it is clear for everyone, give an example.

(see what I did there?)

I did. However, since it implies "Just so" as the starting words, it's a
sloppy example. Close but no cigar. :-)

So after all this searching for valid examples, we seem no closer to
finding any more than that excellent "So What?" example above (see what I
did *there*?). :-).

Just so I can get back to the question raised by the OP[1], I feel I
should mention that my own oil filled radiator, a 2.5KW SilverCrest
example bought last year from Aldi/Lidle, uses a 4 position rotary
selector switch to provide heating levels of zero (off) 800W, 1200W and
2000W, all under the control of an adjustable thermostat. Furthermore, in
addition to the oil heating element power level options, it includes a
500W fan heater not controlled by any thermostat other than by the
standard overheat cut out stat which is operated independently of the oil
heater circuitry by a simple on/off switch with its own neon indicator.

The plastic power level selector and thermostat control knobs have a
smooth satin finish which makes the power selector switch awkward to
operate for lack of 'grip'. It is notable that the (10A rated) 2 metre
Silicone rubber mains lead becomes a little warmish only after switching
on the fan heater when running on the 2KW maximum setting. I'm guessing
the additional 10 watts or so dissipated in the mains lead must have been
considered as a "bonus source of additional heat" by the designers. :-)

Obviously, the oil heater section will draw the power selected by the
power selector switch until the thermostat cuts out (assuming the stat
was set for an achievable temperature).

[1] This thread has become rather disjointed in my news client (Pan) to
the extent that I wasn't able to locate the OP to check the original
question. However, it looks like he, as best as I can tell, was querying
why the use of 5 similar type oil heaters were tripping out a 45A circuit
breaker.

Since the heater elements have virtually a zero temperature coefficient
of resistance, there's no issue of cold switch on surge loading to
contend with so the only other variables are the chosen power settings
and the effect of the thermostat switching the heating element(s) load on
and off.

A gander at the rating plate should tell him all he needs to know
(notably, the maximum power rating and the nominal voltage - typically
since harmonisation, 230v). In some cases, the label may even show a
second higher wattage rating for 240v. In any case, since the heating
elements are a fixed resistance value, it's a fairly trivial task to
calculate the 240v loading from the 230v figures if more precision is
needed.

--
Johnny B Good

"Johnny B Good" wrote in message
...
**** snipped
Christ on a bike, are you for real?
If you're cold you switch on the heating, otherwise, you don't. Watts are
watts wherever you use them.
However, I formally suggest that you are the king of typing ********. Dave
is beaten into 2nd place.

On 12/11/2017 01:55, Johnny B Good wrote:

A gander at the rating plate should tell him all he needs to know
(notably, the maximum power rating and the nominal voltage - typically
since harmonisation, 230v). In some cases, the label may even show a
second higher wattage rating for 240v. In any case, since the heating
elements are a fixed resistance value, it's a fairly trivial task to
calculate the 240v loading from the 230v figures if more precision is
needed.

Quite allot of stuff specced for the UK market will quote the power
assuming its running on the genuinely manly 240V rather than the nominal
girly 230 euro volts.

So 2kW @ 240V suggests a load of about 29 ohms. So the actual power
could be anything from 1608W to 2207W if you swing across the full
permitted nominal 230V range of 216V to 253V


--
Cheers,

John.

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

On 08/11/2017 22:24, Tim Watts wrote:
On 08/11/17 22:00, pamela wrote:

36A is a lot. Wouldn't that melt the insulation on the wires?


No. The current carrying capacity of a cable is determined by (mostly)
how hot it gets.

A ring final circuit is designed to run forever at 32A with a max of 20A
in any part of the cabling.

And maybe as much as 27A (for 2.5mm^2 T&E) depending on how its installed.

So unless you are right up one end of the ring, 36A would quite possibly
never take either leg of the ring to max cable conductor temperature.



--
Cheers,

John.

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

On 09/11/2017 13:21, pamela wrote:
On 22:24 8 Nov 2017, Tim Watts wrote:

On 08/11/17 22:00, pamela wrote:

36A is a lot. Wouldn't that melt the insulation on the wires?


No. The current carrying capacity of a cable is determined by
(mostly) how hot it gets.

A ring final circuit is designed to run forever at 32A with a
max of 20A in any part of the cabling.

I thought it was 13A because that is the max rating for an plugged in
appliance.

A ring circuit can supply many sockets over a floor area of up to
100m^2. So even if the individual load on a single plug does not exceed
13A, the total load on the circuit can be much greater.

So does that means I could safely run two 10A appliances from the
same wall outlet?

Modern double sockets are nominally specced at 20A continuous load. Good
quality ones will tolerate 26A of load for a reasonably period -
although perhaps not continuously.


--
Cheers,

John.

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

On Sun, 12 Nov 2017 01:55:21 GMT, Johnny B Good
wrote:

snip

Obviously, the oil heater section will draw the power selected by the
power selector switch until the thermostat cuts out (assuming the stat
was set for an achievable temperature).

snip

I'm guessing your 'obviously' above is assumed? ;-)

The OP could also have assumed that the power drawn would relate
directly to the switch settings and the thermostat but it seems it
does not.

Cheers, T i m

On Sun, 12 Nov 2017 02:23:24 -0000, "bm" wrote:


"Johnny B Good" wrote in message
...
**** snipped
Christ on a bike, are you for real?
If you're cold you switch on the heating, otherwise, you don't. Watts are
watts wherever you use them.
However, I formally suggest that you are the king of typing ********. Dave
is beaten into 2nd place.

Oh the irony!

You are the chief poster of (especially) OT bollox here and I think
the depth of said bollox is getting more and more desperate and
bizarre. ;-(

Tip for you .... 'Do not open mouth until brain is in gear'.

Cheers, T i m

On Sun, 12 Nov 2017 04:00:43 +0000, John Rumm wrote:

On 12/11/2017 01:55, Johnny B Good wrote:

A gander at the rating plate should tell him all he needs to know
(notably, the maximum power rating and the nominal voltage - typically
since harmonisation, 230v). In some cases, the label may even show a
second higher wattage rating for 240v. In any case, since the heating
elements are a fixed resistance value, it's a fairly trivial task to
calculate the 240v loading from the 230v figures if more precision is
needed.

Quite allot of stuff specced for the UK market will quote the power
assuming its running on the genuinely manly 240V rather than the nominal
girly 230 euro volts.

So 2kW @ 240V suggests a load of about 29 ohms. So the actual power
could be anything from 1608W to 2207W if you swing across the full
permitted nominal 230V range of 216V to 253V

Indeed! As a matter of fact, I just spotted a response by ARW to this
thread just after posting wherein he considerately quoted the attribution
by Whiskey Dave who had posed the question as to why a test load of five
such heaters had failed to trip the 32A circuit breaker on a lab bench
supply of ,oddly, 220v.

To reiterate, WD had asked us to guess the actual wattage in spite of
getting what I thought in the circumstance of the supply dropping from
220v down to a mere 202 volts (presumably with all five heaters plugged
in - it would be extremely worrying indeed if this voltage drop was the
result of just one heater), a rather accurate 1.6KW reading on his
inexpensive Maplin energy consumption meter. A drop in power from the 2KW
(presumed to be specified for a 230v supply) level down to 1.6KW on a
202v supply is exactly what one would expect.

Assuming a 1.6KW load at 202v, I calculate a heater resistance value of
25.5 ohms which neatly ties in with a 230v rating of 2KW. The amperage at
202 volts is a mere 7.92. For five such heaters, this represents a total
loading of 39.6A which won't immediately trip a 32A circuit breaker.

As ARW succinctly pointed out, the problem would appear to be a wiring
issue (compounded imo, by the strange choice of 220v rather than the more
typical 240v of a UK mains supply). If the bench supply had stayed at the
220v level WD's test setup would have resulted in a current of 43.13A
which may still not have tripped the breaker in a timely fashion.

Even assuming that the mention of a 220v supply was a typo for 230v, the
current would have only increased to 45.1A on 230v, rising to 47A on a
240v supply. WD really needed to use 6 or 7 such heaters to test trip
that 32A circuit breaker. TBH, I'm amazed that WD couldn't figure all of
this out instead of making a fool of himself in this NG by asking such a
foolish question to which he already had all the data he needed to
provide the answer he sought.

--
Johnny B Good

Johnny B Good wrote:

on a lab bench supply of ,oddly, 220v.

Maybe the college has been sold a system to regulate the site voltage
down to 220V for "cost savings".

I know of an NHS estates dept that fell for that for a datacentre, and
wouldn't hear a word of it when I said the UPS and SMPUs would merely
take higher current (or the same current through more of the mains
cycle) to make up for the lower voltage, and the aircon units would have
to run for longer cycles, I suppose there would be a minor saving from
the fluorescent lights being a bit dimmer ...

Or maybe another lab at the college got in first with their bank of oil
heaters that took the supply down from 240V to 220V?

On Friday, 10 November 2017 19:55:35 UTC, T i m wrote:
On Fri, 10 Nov 2017 04:31:50 -0800 (PST), whisky-dave
wrote:

snip

Sounds like it's the upper limit stat that is cutting in and out on
the bigger element (only) ... before the main stat cuts everything
out? Do you have a IR thermometer? If so it might be interesting to
see what surface temperatures these clicks and measurements apply to.

We do have an IR thermo... good idea, providing I can find it.

;-)

What temperature would you expect say the half way up the fin should be.
I know it's to hot to hold on to as I tried.

I can't say for your rad but when I was experimenting with mine I
think it was pretty high ... as I think the thermal trip was set at
110 DegC or summat (but that may be wrong).

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


So, if you hear something click and the wattage from 2000 to 700, but
turning the main stat down sees the current drop to zero, the thought
is that the upper limit stat is cutting the power to the main element
(because the rad is overheating itself) before the main (room-ish)
temp stat is cutting the power to it all?

That seems to be what is happening.


So, with the IR thermometer looking say midway up the rad, and you
monitoring the power drawn, see if you can work out a pattern between
the clicks, lights and temperature.

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


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.
I thought that's what all cut-outs did.



If you turn the stat down to just above the current temperature, you
may find that (the main stat) will cut out (0W) before the overtemp
stat (leaving 700W).


If they are keeping them I'd be inclined to open one up and make a
wiring diagram (or see if there is one in there or in the manual).

The manual is on line and has the same details as the one supplied in the box.

Ok.

When you say 'they' it is the estates department I doubt they'd like me taking their new stuff apart and I don't particually want to.

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

What plastic end cover ?


I have an oil filled radiator at home that works as I'd expect it to, but then that one was over £100 rather than £35.

Shouldn't make any difference what it cost to how it works.

I think it does as it does with almost anything else and my home one is 2.5KW.

On Saturday, 11 November 2017 15:10:34 UTC, ARW wrote:
On 08/11/2017 12:25, whisky-dave wrote:

As some might have read we've been supplied with a number of oil filled radaitors

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

So I unpacked them and installed them, one by one.

In an attempted to trip our 32 amp circuit braker I would have thought that 5 would have done it, but they didn't.

On switch on they started at about 1.6KW (using an old maplin power meter)
I left them fully on, that's the highest setting .

The lab voltage dropped from the 220V to about 202V so that accounts for it I guess.

But what realy suprised me was the power consumption of a radiator when it was full on, anyone care to guess what it was.

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, 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.

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

On Friday, 10 November 2017 18:18:54 UTC, John Rumm wrote:
On 09/11/2017 15:12, whisky-dave wrote:
On Thursday, 9 November 2017 14:54:23 UTC, T i m wrote:

So are you asking why it's currently showing ~700 W or why it's
fluctuating around 700W

Yes why is a 2KW heater only drawing 700W when fully on, if it was up
to temperatury I'd expect it to disconneced with a bimetalic strip or
something more advanced and would be 0W not 700W.

It would suggest it is not "fully on". It might be that the stat does
not fully disconnect both elements - perhaps just the 1300W one. If that
were the case it would cycle between ~2kW and 700W during normal operation.

Note also that some heaters are configurable. I found some wall mounted
2kW fan heaters I ordered a while back actually ran at a default max of
1kW unless you set an internal switch to allow the full 2kW.

That seems to be true with bathroom down heaters but not with others.

On Sunday, 12 November 2017 01:55:24 UTC, Johnny B Good wrote:


A gander at the rating plate should tell him all he needs to know
(notably, the maximum power rating and the nominal voltage - typically
since harmonisation, 230v).

As I've posted previously.
220-240V 50Hz 2000W.
So does that mean it doesn't matter whether the voltage is 220 or 240 it'll always use 2000W not 1999 or 2001 exactly 2000.

Seems you expect rather a lot of tech info from a stick on label.


In some cases, the label may even show a
second higher wattage rating for 240v. In any case, since the heating
elements are a fixed resistance value,



it's a fairly trivial task to
calculate the 240v loading from the 230v figures if more precision is
needed.



--
Johnny B Good

On Sunday, 12 November 2017 14:48:27 UTC, Johnny B Good wrote:
On Sun, 12 Nov 2017 04:00:43 +0000, John Rumm wrote:

On 12/11/2017 01:55, Johnny B Good wrote:

A gander at the rating plate should tell him all he needs to know
(notably, the maximum power rating and the nominal voltage - typically
since harmonisation, 230v). In some cases, the label may even show a
second higher wattage rating for 240v. In any case, since the heating
elements are a fixed resistance value, it's a fairly trivial task to
calculate the 240v loading from the 230v figures if more precision is
needed.

Quite allot of stuff specced for the UK market will quote the power
assuming its running on the genuinely manly 240V rather than the nominal
girly 230 euro volts.

So 2kW @ 240V suggests a load of about 29 ohms. So the actual power
could be anything from 1608W to 2207W if you swing across the full
permitted nominal 230V range of 216V to 253V

Indeed! As a matter of fact, I just spotted a response by ARW to this
thread just after posting wherein he considerately quoted the attribution
by Whiskey Dave who had posed the question as to why a test load of five
such heaters had failed to trip the 32A circuit breaker on a lab bench
supply of ,oddly, 220v.

Why oddly at 220V I don't think I've seen it much higher.


To reiterate, WD had asked us to guess the actual wattage in spite of
getting what I thought in the circumstance of the supply dropping from
220v down to a mere 202 volts (presumably with all five heaters plugged
in -

Yes all on ONE phase from ONE MCB breaker.


it would be extremely worrying indeed if this voltage drop was the
result of just one heater), a rather accurate 1.6KW reading on his
inexpensive Maplin energy consumption meter. A drop in power from the 2KW
(presumed to be specified for a 230v supply) level down to 1.6KW on a
202v supply is exactly what one would expect.

That's about it.


Assuming a 1.6KW load at 202v, I calculate a heater resistance value of
25.5 ohms which neatly ties in with a 230v rating of 2KW. The amperage at
202 volts is a mere 7.92. For five such heaters, this represents a total
loading of 39.6A which won't immediately trip a 32A circuit breaker.

Yes this is what we found we didn't expect immidiate unless all heaters were switched on at the same time,it was a trial to see what would happen if someone strted up everything at the same time, but it was over 2 hours before it tripped out.


As ARW succinctly pointed out, the problem would appear to be a wiring
issue (compounded imo, by the strange choice of 220v rather than the more
typical 240v of a UK mains supply). If the bench supply had stayed at the
220v level WD's test setup would have resulted in a current of 43.13A
which may still not have tripped the breaker in a timely fashion.

Well the idea was that we didn't want the power tripping during a lab or lecture so tried running worse case senerio with what we had to hand.



Even assuming that the mention of a 220v supply was a typo for 230v,


which it wasn't my office with ONE heater at 700W , 212V dropping to 211 when the heater switches to 1.7KW.


the
current would have only increased to 45.1A on 230v, rising to 47A on a
240v supply. WD really needed to use 6 or 7 such heaters to test trip
that 32A circuit breaker. TBH,

I didn;t have 6-7 heaters at the time just 5 .



I'm amazed that WD couldn't figure all of
this out instead of making a fool of himself in this NG by asking such a
foolish question to which he already had all the data he needed to
provide the answer he sought.

That wans't my original question that is why, and you've avioded the original Q.

If yuo have a 2KW heater switched to full on what is it;s power consumption adn of course you''ve got that wrong it's NOT 2KW not 1.6KW not even 1.4KW not even 1KW but 700W .

SO like opur so calledheating engineers must have done hopw many 2KW heaters does it take to raise the temperature from 14C to 16C.

How dos that change is the 2KW heaters donlt give out 2KW but only 700W how does that change teh calculation.


Now the original heating system was put in in the 50s , the engineers told the college that they system wasn't designed for such a long run through 2-3 departments i;e the heating conduit path was too long to maintaine the temperture. This is why the lectures offices get really hot so they academics open their doors and windows and by the time the heating conduit gets into the lab the air is almost cold if not colder than the outside temperature..

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. ?

On Mon, 13 Nov 2017 05:06:37 -0800 (PST), whisky-dave
wrote:

On Friday, 10 November 2017 19:55:35 UTC, T i m wrote:
On Fri, 10 Nov 2017 04:31:50 -0800 (PST), whisky-dave
wrote:

snip

Sounds like it's the upper limit stat that is cutting in and out on
the bigger element (only) ... before the main stat cuts everything
out? Do you have a IR thermometer? If so it might be interesting to
see what surface temperatures these clicks and measurements apply to.

We do have an IR thermo... good idea, providing I can find it.

;-)

What temperature would you expect say the half way up the fin should be.
I know it's to hot to hold on to as I tried.

I can't say for your rad but when I was experimenting with mine I
think it was pretty high ... as I think the thermal trip was set at
110 DegC or summat (but that may be wrong).

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, if you hear something click and the wattage from 2000 to 700, but
turning the main stat down sees the current drop to zero, the thought
is that the upper limit stat is cutting the power to the main element
(because the rad is overheating itself) before the main (room-ish)
temp stat is cutting the power to it all?

That seems to be what is happening.

Ok.


So, with the IR thermometer looking say midway up the rad, and you
monitoring the power drawn, see if you can work out a pattern between
the clicks, lights and temperature.

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.


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.

I thought that's what all cut-outs did.

You would think ... however, it may be that the actual switch they use
can't handle the extra 700W or it was considered that the 700W element
couldn't get the rad into an overtemp condition or it was just badly
designed or incorrectly wired.



If you turn the stat down to just above the current temperature, you
may find that (the main stat) will cut out (0W) before the overtemp
stat (leaving 700W).


If they are keeping them I'd be inclined to open one up and make a
wiring diagram (or see if there is one in there or in the manual).

The manual is on line and has the same details as the one supplied in the box.

Ok.

When you say 'they' it is the estates department I doubt they'd like me taking their new stuff apart and I don't particually want to.

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).


I have an oil filled radiator at home that works as I'd expect it to, but then that one was over £100 rather than £35.

Shouldn't make any difference what it cost to how it works.

I think it does as it does with almost anything else and my home one is 2.5KW.

I'm saying 'it shouldn't'. 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).

Cheers, T i m

On Monday, 13 November 2017 15:26:02 UTC, T i m wrote:
On Mon, 13 Nov 2017 05:06:37 -0800 (PST), whisky-dave
wrote:

On Friday, 10 November 2017 19:55:35 UTC, T i m wrote:
On Fri, 10 Nov 2017 04:31:50 -0800 (PST), whisky-dave
wrote:

snip

Sounds like it's the upper limit stat that is cutting in and out on
the bigger element (only) ... before the main stat cuts everything
out? Do you have a IR thermometer? If so it might be interesting to
see what surface temperatures these clicks and measurements apply to.

We do have an IR thermo... good idea, providing I can find it.

;-)

What temperature would you expect say the half way up the fin should be.
I know it's to hot to hold on to as I tried.

I can't say for your rad but when I was experimenting with mine I
think it was pretty high ... as I think the thermal trip was set at
110 DegC or summat (but that may be wrong).

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.

So what does a cut-out do.




So, if you hear something click and the wattage from 2000 to 700, but
turning the main stat down sees the current drop to zero, the thought
is that the upper limit stat is cutting the power to the main element
(because the rad is overheating itself) before the main (room-ish)
temp stat is cutting the power to it all?

That seems to be what is happening.

Ok.


So, with the IR thermometer looking say midway up the rad, and you
monitoring the power drawn, see if you can work out a pattern between
the clicks, lights and temperature.

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.


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.


I thought that's what all cut-outs did.

You would think ... however, it may be that the actual switch they use
can't handle the extra 700W or it was considered that the 700W element
couldn't get the rad into an overtemp condition or it was just badly
designed or incorrectly wired.

So many options to consider one wonders how yuo;d calculate how many heaters would be needed, it;s a problem we're having at this very moment and discussing , how many more to buy and who should pay for them.


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 and if I did it would then fail regualtaions as we;d need it PAT tested before it was put back into use.
So another reason njot to take it apart, I'd prefer that we were supplied with working equipment that was up for the job.


I have an oil filled radiator at home that works as I'd expect it to, but then that one was over £100 rather than £35.

Shouldn't make any difference what it cost to how it works.

I think it does as it does with almost anything else and my home one is 2.5KW.

I'm saying 'it shouldn't'.

Well it does just like anything else, or at least you should expect it to.



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).

Cheers, T i m

Nothing of which help work out how many we need.
Perhaps that's why we have 14 due to arrive this week.

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").



--
Cheers,

John.

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

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.


--
Cheers,

John.

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

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 ?
What are the things you need to know ?

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

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 ?


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

how do you work that out ?


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.


[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.

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


(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.


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

Indeed it is.


--
Cheers,

John.

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

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.

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.

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'.


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.


I thought that's what all cut-outs did.

You would think ... however, it may be that the actual switch they use
can't handle the extra 700W or it was considered that the 700W element
couldn't get the rad into an overtemp condition or it was just badly
designed or incorrectly wired.

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

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).

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.

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


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?

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. ;-)

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? To do that you would first have to speak to the
suppliers and they in turn to the wholesalers and possibly the
manufacturers.

snip

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 (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