Testing heating elements

[EFLImpudence]

You're asking that the wrong way round.

He did get 22Ω.
Therefore if there are three elements and one IS open circuit that means the heater should be 3.6kW - @ 230V.

Although I think the values would be at 240V which would be 3.9kW.
I think that is higher than normal so I would presume the three - or two - are alright.

 

[JohnW2]

John, your good at maths, what if one element was open circuit what reading would he get.

I'm not sure what question you are asking there - since we know that he got 22Ω.

If he got 22Ω with three in parallel, but one O/C (i.e. with just two of them in parallel), then they would be 44Ω each, so that 3 (if all OK) in parallel would have been about 14.7Ω (44/3) - which would mean that, with all three working, it would be about 3.6 kW (at 230V) or about 3.9 kW (at 240V) total with all three elements working.

Kind Regards, John
Edit: Whoops - I didn't 'turn the page' and see EFLI's post - but at least we agree!

 

[JohnW2]

Although I think the values would be at 240V which would be 3.9kW. I think that is higher than normal so I would presume the three - or two - are alright.

If it's actually true that there is 22Ω across the elements (no matter whether 1, 2 or 3 of them are OK), then if they were getting 230V, some ~2.4kW would be going somewhere, but the OP seems to be saying that no heat is being produced - so one presumably has to conclude that 230V (or whatever) is not getting to the element(s).

Kind Regards, John

 

[EFLImpudence]

Oh, yes. I was only answering Rocky's question.

 

[JohnW2]

Oh, yes. I was only answering Rocky's question.

Same here (because I hadn't seen that you already had)

However, the point remains that, on the basis of what we've been told, at least one (and quite possibly two or three) of the elements are OK - so, if no heat is being produced, electricity cannotbe getting to it/them.

Kind Regards, John

 

[333rocky333]

I'm not sure what question you are asking there -

No worries, I was being lazy
I believe Resistance in parrallel you add the reciprocals. which i am no good at, though i suppose i could use google nowadays.

Thats why in the past i measured each element isolated to find the faulty one.

Therefore what i was asking is if its say labelled as a 3.4kw heater and had 4 elements
What readings should he expect if tested like he did with all 4 still connected.
If
4 ok none open circuit
3 ok 1 open circuit


I seem to recall elements being about 800w each

 

[EFLImpudence]

Does anyone know what these two pins do? Looks a bit odd.
It says 'DUAL' above them - upside down.

 

[333rocky333]

On his old post he found the manual, to me it looks like you can easily bypass the gubbins to test the elements

https://www.manualslib.com/manual/1069980/Creda-Eco-Response-Er300.html?page=3#manual

 

[EFLImpudence]

I believe Resistance in parrallel you add the reciprocals. which i am no good at, though i suppose i could use google nowadays.

No, parallel - if they are all the same, divide by the number. E.g. Three at 66Ω = 22Ω.

Therefore what i was asking is if its say labelled as a 3.4kw heater and had 4 elements
What readings should he expect if tested like he did with all 4 still connected.

It doesn't matter how many R = V²/P 240² / 3400 = 16.9Ω
So if there were 4 then each 16.9 x 4 = 67.6

4 ok none open circuit = 16.9Ω
3 ok 1 open circuit = 67.6 / 3 = 22.5Ω - could be that but three would still work.

I seem to recall elements being about 800w each

Yes, so either 2.4kW or 3.2kW

 

[JohnW2]

No worries, I was being lazy I believe Resistance in parrallel you add the reciprocals. which i am no good at ....

Yes, add the reciprocals and then take the reciprocal of the answer. However, if (as we're assuming here) all the resistances are equal, then i's much easier - since you then just 'divide by N' (N being the number of equal resistances that are in parallel) - e.g. if you have 5 resistors, each of 50Ω, in parallel, then the combined resistance is 50Ω/5 = 10Ω.

If there are just two (unequal) resistances in parallel, then you might find it easier to remember (rather than the reciprocal thing) ...

(R1 x R2) / (R1 + R2) .... i.e (R1 times R2) divided by (R1 + R2). Therefore what i was asking is if its say labelled as a 3.4kw heater and had 4 elements ... What readings should he expect if tested like he did with all 4 still connected.
If ... 4 ok none open circuit ... 3 ok 1 open circuit .... I seem to recall elements being about 800w each[/QUOTE]If each were 800W at 240V, that would be a resistance of 72Ω each.

As above, with equal resistances it's easy. If each is 72Ω and all 4 are working, then the 'combined' resistance would simple be 72Ω divided by 4 - i.e. 18. If only 3 were working, it would be 72 divided by 3 - i.e. 24Ω.

Kind Regards, John

 

[JohnW2]

Hmmm - this game again. Anyway, I think there may be ways around this 'awaiting moderation'. How about ....

 

[EFLImpudence]

Yes, message here too.



Page 1 of manual:

What does the 0.39kW mean?

Anyway, 2.6kW with four elements is 0.65kW each = 88Ω / 4 = 22Ω.

 

[333rocky333]

Ah that all makes sense, i was not doing reciprocal of the total.
Looking at the ops previous thread it appears to have 4 elements

 

[Custom45]

Thanks again for the replies, just got off a plane to find them.

The off peak storage heater is 2.6kw.
The separate peak "top up" radiant panel is 0.39kw (this kicks in during the day as & when needed to maintain temperature when the bricks lose heat). The 0.39kw panel works fine, it's just the off peak that isn't producing heat.

Rocky is right, it has 4 elements, I thought it only had 3, so I only tested 3. The precise reading for each was fairly stable on 22.7ohms. I'll test the 4th when I'm home tomorrow.

Based on what's being said I'm still thinking a fault with the off peak part of the control module where it's got power to it, but a fault is preventing it sending anything out to the elements? 0.39kw peak panel works off same control module.

Cheers,

 

[333rocky333]

If your testing with the elements still having the wires connected, you will get the same reading at each element, so no point testing the 4th one .

This is what the above discussion was about.
Even if 1 or more elements was faulty the reading taken at each element, with them connected will always be the same, but the reading, value in ohms, will get progressively higher, in relation to each dodgy element.
This is because they are all connected in parallel
As EFLI said above 22 ohms is typical for your heater when all 4 elements are fine