Bosch Fan Oven Trips RCD

[actsafe]

Bosch HBN 9150 GB/01 double oven

Bottom oven trips the house RCD after a few minutes of heating up.

Have removed the back panel inside the oven to expose the element and inspected no obvious disintegration of the element casing as shown in some of the pictures on this website.

When turn oven on element will get red hot before the RCD trips. The fan inside the element in the oven does not rotate.

I cannot remember whether the fan should start to rotate as soon as the oven is turned on or whether it kicks in once a certain temperature is reached?

My favourite suspect for the RCD trip was the element heating up and the coil touching the element casing when it heats up, however the fan not working is now confusing me.

Would appreciate your expert opinions before i start ordering spare parts.

Many thanks in advance

Andrew

[superfix]

Re: Bosch Fan Oven Trips RCD

Fan should kick in straight away.

I would suspect the earth fault will be on the element, as you say the insulation will be breaking down as it gets hotter.

Only way to know for sure is to megger the element.

Power off please first :zap:

[actsafe]

Re: Bosch Fan Oven Trips RCD

Thanks for the advice.
If it helps anyone else heres what i did and found.
Powered off and removed back panel.
Borrowed PAT tester (Not Megger tester) and insulation tested (500V) fan element and fan motor spearately. Both passed.

Removed both parts. NOTE The fan on the front is a left hand thread (I didn’t have the new part or know this when i tried to remove it) hence i managed to lock the fan to the shaft which then just rotated relative to any part i could could get hold of. Cut the shaft in half at the rear with a junior hacksaw to release.

Decided to replaced fan motor first. Replaced with a new fan motor assembly (bought from UKWG) and refitted old element. Oven works perfectly. I ordered a element at the same time as a backup.

I must conclude that the element gets significantly hotter than it should without the fan, causing element coil to move and trip RCD. RCD protects element from total destruction. Once element cools insulation is restored hence passes PAT insulation test.

Also worth noting I priced parts (Fan mtor and element) from UKWG (~£75) and direct from Bosch parts (~£140). Element i undersatnd is pattern part but motor is same supplier Bosch use. Good saving.

Thanks for your hekp

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