Recalled Wylex RCD faulty?? Trouble with oven

[kathb0110]

Hi, hopefully someone can shed light on this.

We have a house that has been completely re-wired with a Wylex CU - unfortunately one of the ones that has recall issues. Everything worked okay for 2 months, but then the oven which is hard wired with the hob on a separate circuit, started tripping the RCD. This was after 20 minutes or so being switched on, the hob was not in use, only the main oven. To check, the oven has had a plug put on and is plugged in to a standard 13amp socket, which is on the other side of the CU, therefore a different RCD and everything works okay.

I have waited 4 weeks for Electrium to get someone out to see us, to check whether it's a faulty CU, but all they were sent to do was check the relevant fuses on recall.

So now I'm stuck, what do I do? What is faulty - logic says it can't be the oven, so is it the RCD?

Any help much appreciated.

 

[flameport]

What is faulty - logic says it can't be the oven, so is it the RCD?

Probably is the oven.

The oven has some minor fault, and due to this a small amount of current flows to earth when it is in use. On it's own this is not enough to trip the RCD.

The RCD that the oven is usually wired to has other circuits, and one or more of them has appliances or defects which cause another small amount of current to flow to earth. This is also not enough to trip the RCD, but combined with the oven, the total will cause the RCD to trip.

It works on the other RCD, because the circuits connected to that don't supply other leaky appliances, or that RCD has a slightly higher trip current.

 

[kathb0110]

Thanks for your reply.

When we tested the oven, we'd switched all the other MCBs on the same RCD off and the hob was off, although still "live" and the RCD tripped after 20 miutes or so of the oven being used. The RCD that the oven/hob circuit is on is bigger than the one on the other side of the CU, that the oven is currently plugged in to on the kitchen ring.

I hope this makes sense, with this scenario do you still think it's the oven?

 

[1john]

I think the Electrium recall was for faulty MCB's.

 

[kathb0110]

Yes it was for MCB's, but the guy who came logged our fault too. Not sure if RCD's on a CU are the same as drip tap on the boiler, the drip tap leaks and you have to have that bit fixed, so it can work correctly - but trying to figure out if the RCD is broken or the oven is doing strange things is a minefield

 

[ELZ4742]

there was a fault with 6a steeple mcbs which are made by electrium (crabtree) recently, did they state which ones were on the recall?

 

[Taylortwocities]

Thanks for your reply.

When we tested the oven, we'd switched all the other MCBs on the same RCD off and the hob was off, although still "live" and the RCD tripped after 20 miutes or so of the oven being used. The RCD that the oven/hob circuit is on is bigger than the one on the other side of the CU, that the oven is currently plugged in to on the kitchen ring.

I hope this makes sense, with this scenario do you still think it's the oven?

Turning off the MCBs only removes the live connection from the RCD. The neutrals will still be connected and the RCD will trip if an earth fault occurs on either the neutral or the live connection.

 

[kathb0110]

ours ws one of the SF17NHISS10SLAB WYLEX 10 WAY DUAL RCD BOARD that was recalled

 

[ban-all-sheds]

Swap the RCDs around.

Tripping behaviour stays with the same physical position: flameport's analysis is correct.

Tripping behaviour moves with the RCD: RCD is faulty OR more sensitive.

What are the figures for the RCDs on the schedule of test results?

 

[1john]

Get a sparky to test the RCD in isolation and then insulation resistance test the circuits individually. Does this RCD perhaps feed the oven / hob / kitchen sockets / boiler / outside lights??

 

[kathb0110]

Just looking at the test sheets, not sure of the technical bit of info you need, there are only the oven/hob and downstairs sockets (not kitchen) and upstairs lights on the affected RCD. The "functional testing RCD time" is lights 26ms sockets 27ms and oven/hob 26ms. If this is the figure you are after. The " insulation resistance" is lights >768 >894 sockets >1000 >1000, oven/hob >1000 >1000.

 

[1john]

my money is on the oven being at fault