cooker element readings

[EddieB]

I have measured the following readings to earth on a twin oven---- Element 1... 0.149, Element 2... 0.9, Element 3... 0.88 , Element 4 0.08. These all with the merger set at 500v. they all seem low to me especially Element 4, needless to say the RCD trips randomly.

 

[freddo]

I assume you disconnected all the wires to the elements before measuring? Or the common neutral will provide misleading readings, some elements my also be linked together during certain selector switch positions as well. Unusual for so many to be low unless the oven hasn't been used in a while.

Might be worth running each element for 20 minutes or so and re test again. If they are still low, replacing the elements is likely the only solution.

If there is damp in the elements mineral insulation, the reading will often get even lower when it's hot, until the moisture has been driven out.

 

[EddieB]

I assume you disconnected all the wires to the elements before measuring? Or the common neutral will provide misleading readings, some elements my also be linked together during certain selector switch positions as well. Unusual for so many to be low unless the oven hasn't been used in a while.

Might be worth running each element for 20 minutes or so and re test again. If they are still low, replacing the elements is likely the only solution.

If there is damp in the elements mineral insulation, the reading will often get even lower when it's hot, until the moisture has been driven out.

I assume you disconnected all the wires to the elements before measuring? Or the common neutral will provide misleading readings, some elements my also be linked together during certain selector switch positions as well. Unusual for so many to be low unless the oven hasn't been used in a while.

Might be worth running each element for 20 minutes or so and re test again. If they are still low, replacing the elements is likely the only solution.

If there is damp in the elements mineral insulation, the reading will often get even lower when it's hot, until the moisture has been driven out.

Hi Freddo. I did I removed all the wiring and tested the element only, however the lady who owns the cooker only uses it every now and again

 

[EddieB]

I assume you disconnected all the wires to the elements before measuring? Or the common neutral will provide misleading readings, some elements my also be linked together during certain selector switch positions as well. Unusual for so many to be low unless the oven hasn't been used in a while.

Might be worth running each element for 20 minutes or so and re test again. If they are still low, replacing the elements is likely the only solution.

If there is damp in the elements mineral insulation, the reading will often get even lower when it's hot, until the moisture has been driven out.

I disconnected everything and tested, the lady who owns the cooker doesn't use it very often, that said those element readings shouldn't be that low surely

 

[ipf]

I have measured the following readings to earth on a twin oven---- Element 1... 0.149, Element 2... 0.9, Element 3... 0.88 , Element 4 0.08. These all with the merger set at 500v. they all seem low to me especially Element 4, needless to say the RCD trips randomly.

Sounds like a merger between elements.

I agree about running them individually.

How do they test continuity wise?

 

[timhoward]

I have measured the following readings to earth on a twin oven---- Element 1... 0.149, Element 2... 0.9, Element 3... 0.88 , Element 4 0.08. These all with the merger set at 500v. they all seem low to me especially Element 4, needless to say the RCD trips randomly.

Barely used elements present difficulties as they have absorbed moisture.
The quick diagnosis is an earth leakage clamp meter and turn each on in turn.
The slower process is to ramp test the RCD with each element on in turn, you are looking for a really low number of ma causing a trip.
You could then wait a couple of minutes and repeat each element and see if the trip current changes.
(It can sometimes work to run the element in a workshop on a non-protected supply for a while to properly dry it out.)

 

[EddieB]

Barely used elements present difficulties as they have absorbed moisture.
The quick diagnosis is an earth leakage clamp meter and turn each on in turn.
The slower process is to ramp test the RCD with each element on in turn, you are looking for a really low number of ma causing a trip.
You could then wait a couple of minutes and repeat each element and see if the trip current changes.
(It can sometimes work to run the element in a workshop on a non-protected supply for a while to properly dry it out.)

Many thanks for your assistance.

 

[EddieB]

What would you expect to read if you tested a brand new element to earth , I would a reading in the high MOhms not the readings I posted , it just seems strange that they are all low but as I mentioned this oven is rarely used

 

[freddo]

To earth a good element should read off the scale of a standard 500V insulation tester. You would want the whole oven to measure at least 1Mohm when the appliance is tested as a whole, preferably much higher than this! For cookers greater than 3KW the permitted value is less than 1Mohm but I can't remember what it is. (0.3Mohm rings a bell but I'm not near the book to look it up.)

Modern elements seem to be really poor at keeping the damp out, the amount of brand new cookers that immediately trip RCD is a nightmare.

 

[EddieB]

To earth a good element should read off the scale of a standard 500V insulation tester. You would want the whole oven to measure at least 1Mohm when the appliance is tested as a whole, preferably much higher than this! For cookers greater than 3KW the permitted value is less than 1Mohm but I can't remember what it is. (0.3Mohm rings a bell but I'm not near the book to look it up.)

Modern elements seem to be really poor at keeping the damp out, the amount of brand new cookers that immediately trip RCD is a nightmare.

Thanks Fredo, I agree I was expecting to see the readings in the high MOhms. I’ve looked at the readings and calculated the leakage to around 3 milliamperes, I’ll put a RCD clamp meter on tomorrow and see what it reads throughout the installation.