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