Troubleshooting an oven – running out of ideas

[Mark Flint]

The oven is a Rangemaster Classic Toledo 110 Dual Fuel. The problem is that the fan oven trips the RCD after about 5-10 mins of heating from cold.
Things I have done to troubleshoot:
1) visual inspection of wiring – nothing obvious
2) take the fan motor out of circuit (disconnect) – RCD trips
3) take the lamp out of circuit (disconnect) – RCD trips
4) take the thermal fuse out of circuit (short) – RCD trips
5) take the thermostat out of circuit (short) – RCD trips
6) take the element out of circuit (disconnect) – RCD does not trip
7) run the oven with power to the element but with the oven door open so that temperature does not rise much – RCD does not trip

So, it seems to be related to temperature of the oven, but it still happens with the thermal fuse is shorted out, and the thermostat is shorted out.

Any suggestions for next step?

Thanks, Mark

[kwatt]

Serial number please?

K.

[Kentish]

Have you metered or meggered the elements?
Seen so many ovens of all makes tripping when hot, especially with air fryers being so common

[electrofix]

as Kentish says its most likley the element

Dave

[Mark Flint]

kwatt wrote:Serial number please?

K.

Serial number 7321 158184.

Thanks

[Mark Flint]

Kentish wrote:Have you metered or meggered the elements?
Seen so many ovens of all makes tripping when hot, especially with air fryers being so common

The client replaced the element him self. Both the new one and the old one meter at 22 ohms.

Thanks

[Mark Flint]

electrofix wrote: as Kentish says its most likley the element

Dave

The client replaced the element him self before calling me out. How often would a new element be faulty I wonder – I suppose it could happen.

Thanks

[electrofix]

was it gen or pattern

I dont trust pattern parts these days in elements, too many failures

Dave

gen element part no A094693

[Kentish]

Mark Flint wrote:

The client replaced the element him self. Both the new one and the old one meter at 22 ohms.

Thanks

i never trust anything a customer fits, as most likely it’s the cheapest they can find.
Its not the resistance of the element, but it’s resistance to earth. Everything you have said points to an insulation breakdown, and whilst a good multimeter would show it(my old Fluke went to 500meg ohm on resistance, a megger would show it more easily even when cold.

[Lawrence]

Its the element going down to earth, I bet the customer bought a pattern one of the web, I have stopped using pattern elements for that reason, the fact that when you disconnect the element it doesnt trip tells you everything, test it with the back off and as soon as it trips megger the element from either of the terminals to earth, I bet it will be low resistance, then watch as it cools down it will come back in to range

[Mark Flint]

electrofix wrote:was it gen or pattern

gen element part no A094693

Thanks Dave, I appreciate the part number.

[Mark Flint]

Lawrence wrote:Its the element going down to earth

Thanks Lawrence. It might be time to buy a megga, my DMM is not up to some of these tasks.
Mark

[Mark Flint]

Kentish wrote:
i never trust anything a customer fits, as most likely it’s the cheapest they can find.

Yes, a genuine part will now be fitted.
Thanks, Mark

[Kentish]

Mark Flint wrote:

Yes, a genuine part will now be fitted.
Thanks, Mark

Before you do, I would get a decent DMM with or without insualtion testing (up to 1000v) or buy a stand alone insulation tester.
You cannot test safely and with certainty without it/them.

I myself have a Fluke DMM, which is fantastic but getting long in the tooth.
I also have a Fluke DMM with insulation test that goes up to 2gig.
I also have a stand alone Fluke insulation tested that runs to 11gig.
My prefered options are the first and last, but weight saving means I only carry the middle one in my tool bag

[Mark Flint]

Kentish wrote:

Before you do, I would get a decent DMM with or without insualtion testing (up to 1000v) or buy a stand alone insulation tester.

Thanks for the advice, I’m planning on getting a stand alone megga.
Mark

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