Oven tripping mains supply

[revjames]

I went to a friends mothers house as the oven had gone bang and tripped the supply. Couldnt find anything wrong with the element but couldnt get a supply on to the terminals even though the display was on. Took it out and decided to take it to the workshop for a more thorough look. Realised a bit of faffing was needed with the timer to get element to come on and the bang was the bulb going as it was in tiny fragments inside the cover when I took it off.... Total repair cost £2

 

[mecheng46]

I am tempted to wire the oven and start it without testing anything and see what happens, this will give me a better idea of what the fault is and when it happens instead of relying on what I have been told.

Once i have a better picture and i know what trips and when I can start testing stuff.

Assuming it has an unknown fault, is there any danger of damaging something in the house by connecting it up as it stands?

My fuse board is an old style Wylex and it used to have fuses when i first got in the house. Few years ago i replaced the fuses with this other type below. The picture is just an example, i replaced the old fuses with the same rating.

 

[Murdoch]

I am tempted to wire the oven and start it without testing anything and see what happens, this will give me a better idea of what the fault is and when it happens instead of relying on what I have been told.

Once i have a better picture and i know what trips and when I can start testing stuff.

Assuming it has an unknown fault, is there any danger of damaging something in the house by connecting it up as it stands?

My fuse board is an old style Wylex and it used to have fuses when i first got in the house. Few years ago i replaced the fuses with this other type below. The picture is just an example, i replaced the old fuses with the same rating.

Not picking a fight but your OP said you'd already done that ......

 

[mecheng46]

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.

 

[ProDave]

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.

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

If the owners house does have an rcd it may still trip there, so you may be no further forward.  Other than you can dry all the elements, so if it works in your house, run all the different functions to ensure every element has been heated up for a while.

 

[mecheng46]

i will find out in few hours 

 

[Andy™]

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

 

[Murdoch]

What was said about the fault?

2nd try!

 

[kerching]

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

 

[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

 

[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.

 

[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

 

[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.

 

[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?

 

[UNG]

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

 

[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.

 

[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. 

 

[Andy™]

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

 

[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.

 

[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?