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mecheng46

Oven tripping mains supply

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mecheng46

i will find out in few hours 👍

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Andy™
Just now, ProDave said:

So YOUR house probably does not have an RCD.  It may well run fine in your house.

 

 

which also means his wiring has been more neglected and left untouched. lets hope he doesnt need an RCD to work that one time when he or someone in the house gets a shock

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Murdoch
2 hours ago, Murdoch said:

 

What was said about the fault?

 

 

2nd try!

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kerching
53 minutes ago, mecheng46 said:

not in my house, i only saw the oven connected up in a different place.

 

I tested all the elements and they all seem fine. I am waiting for the food to be cooked on the old oven and i will stick this one in to give it a go.

What did you test  them with and how?

just curious

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mecheng46

tested all 4 elements resistance (L to N and LN to ground) with a fluke and all 4 tested ok (L to N between 30 and 60ohms), no surprises there.

 

I connected the mains cable on the new oven and gave it a go, left both ovens running on full heat for 15 minutes and again no issues.

 

I will let the oven to cool down and I give it another good blast for 1 hour or so and see how it goes.

 

Based on what the previous owner experienced I would say the problem was his 20A circuit breaker, the oven requires 30A fuse which I only found out once I had the oven in my house. I was kind of expecting a heating element to be out or needing drying but it turns out a lot better than i thought, fingers crossed

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ProDave

It won't be the 20A mcb. that might trip after a while with both ovens on, but should not trip with just one.

 

My money is still on an rcd tripping (your house does not have one) and the test meter you used does not sound like a proper insulation tester.

 

At least the elements will have been warmed up, so it may, just may, have fixed it if it was damp elements.

 

Do let us know and if it trips when back in it's own house, take a photo of exactly what trips.

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mecheng46

Picture of the multimeter I used :)

 

The elements warmed up and i left both ovens running at full blast for a while.

 

I will check it again later on.

 

If it was his rcd, what was causing the rcd to trip? Just out of curiocity

IMG-4286.jpg

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ProDave

If one of the elements had an earth leakage fault.  Basically an unwanted resistance path from L or N to earth.  That meter you have would not show that,

 

It's also entirely possible (though unlikely) for a wiring fault within the cooker e.g. a N to E short, or a N and E reversed.

Edited by ProDave

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mecheng46

i have another fluke that does insulation but i thought i won't need it for this job, i left it at work.

 

What is the worst case scenario to test the oven to? Both ovens on, full temp, all 4 elements on, 1 hour?

Edited by mecheng46

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UNG
29 minutes ago, mecheng46 said:

tested all 4 elements resistance (L to N and LN to ground) with a fluke and all 4 tested ok (L to N between 30 and 60ohms), no surprises there.

 

So what did you get L-N to ground

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ProDave

You have to test at the elements.  without power and you setting the clock time, most won't turn on power to the elements.

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mecheng46

this is what i tested, the actual elements at the back of the oven, no power, no cables going to them and i got anything between 30 and 60ohms, I also checked the resistance from LN to earth and I got couple of them a bit more than 1 Mohms and the other two 18Mohms. 

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Andy™
Just now, mecheng46 said:

I also checked the resistance from LN to earth and I got couple of them a bit more than 1 Mohms and the other two 18Mohms. 

 

test again with a proper insulation resistance tester and i bet youll get a lot less than 1meg... even less once its ben heated a bit

Edited by Andy™

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ProDave

I would expect a low voltage multimeter to read open circuit (infinite ohms) between the element terminals and earth.

 

Still now it's all been warmed up it might be okay now.

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mecheng46

been switched on for nearly one hour on all 4 elements, full temperature, no issues.

 

Whilst the oven is out the cupboard, any other tests i need to do or are we confident with it?

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Geoff1946

Personally I would want to know that running it has "cured" the low insulation resistance in those two elements. This can happen when absorbed moisture is driven out of the element's mineral compound.. 

Otherwise, its working, yes, but with an un-detected fault because you don't have an RCD on your panel.

 

Having said that,  (others may correct me here), I believe that until recently it was common to leave cookers off the RCD circuits because they tend to cause this sort of problem.

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mecheng46
1 hour ago, Geoff1946 said:

Personally I would want to know that running it has "cured" the low insulation resistance in those two elements. This can happen when absorbed moisture is driven out of the element's mineral compound.. 

Otherwise, its working, yes, but with an un-detected fault because you don't have an RCD on your panel.

 

Having said that,  (others may correct me here), I believe that until recently it was common to leave cookers off the RCD circuits because they tend to cause this sort of problem.

 

What sort of resistance readings should i get from ''healthy'' elements?

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Geoff1946

A healthy element should be higher than you can read on a general purpose multi-meter. 

An acceptable one,  above 3 or 4 Meg ohms.

As someone else pointed out the resistance can drop as they heat up. (Though without an RCD you will not know).

My theory is that moisture in the insulation is driven towards the ends as the element heats; its concentration in a smaller volume of the insulation creates a leakage path.

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