Fan oven keeps tripping circuit breaker - how to diagnose?

[gutted]

I've a 10 yr old Neff combination oven (B6447N0GB /05) that failed recently, and I can't get a replacement component. I found a brand new oven - exactly the same model and revision - I thought I was sorted, but it arrived damaged So now I have two ovens, and hoping to make a working oven out of the pair. The damaged one looks like it's taken a hefty knock - chassis was dented. It's that one I'd like to fix if I can. Since I have known good components on my other (dead) oven I already switched out the bottom element - but still same symptoms.

Is it worth changing the element around the fan to see if that cures it? Or should I take stock and see if I can actually diagnose the problem before I head down a path of randomly replacing different components?

Full story:
My original one died when the relay/control board failed. A British Gas engineer replaced the control board, but the oven failed again within a couple of weeks - the new control board was diagnosed as faulty (again), but the part is obsolete and we can't get it another.
The brand new oven (still in box) was an eBay find, but arrived damaged. I got a refund, and the seller doesn't want damaged one back. So now I've got a whole load of brand new spares to try and make a decent oven. I've since straightened it out the damaged one and am trying to fix the tripping issue.
I also tried the faulty control board in "new" (damaged) oven and get same symptoms as before - so looks like the replacement board really is faulty.
I could put the board from "new" oven into my old one, but would love to get the "new" one working if I can (but will resort to using new board in original oven if I can't fix this tripping issue).

 

[marconi]

Take the element out and place it in another cold oven. Turn on this oven to 180C and 'cook' for 20 minutes once 180C has been attained. After 20 minutes turn off the oven and allow the oven and element to cool to room temperature - keep the door shut during this cooling. Then refit the element.

 

[gutted]

Thanks for your reply, marconi!

Weirdly I've done almost exactly that. I figured by process of elimination I could pinpoint the cause. I left bottom element in situ and then set oven to use bottom element only, and to cook at 180 deg for about 20 mins. It got up to temp without issue, and is currently cooling. All good. From this I'm thinking that whatever the issue, it's not related to the bottom element. I don't think this function uses the fan.

Next (after it had cooled) I was going to try just using top element - the top one is a single component which is made of the grill element and oven top element joined together.

There's a third component - a ring element - that goes around the fan. I'm not sure if I can tell the oven to just use the ring element one by itself, so unsure how to proceed there, but might identify it as faulty if the top and grill don't cause it to trip.

Previously the oven has tripped the circuit when using "hot air" and "warming" functions, both of which use bottom and top oven element (and fan in both cases, I think).

 

[marconi]

You may be able to identify the leads to the elements and disconnect the elements you do not want energised - in a safe way of course. It is always a good idea to have a 'safety number' with you whose sole but very important job is to ensure that whenever you go near the wiring and innards the electricity is off at the cooker isolator switch.

 

[gutted]

Thanks again, marconi. And yep, I can see the connections to the elements and had wondered whether I might disconnect each in turn - I was trying to figure out a safe way to insulate the connectors though as I don't want live wires dangling around while I'm tinkering

Any tricks of the trade or pro tips on how I can make those wires safe? I was thinking of cutting up some rubber gloves and putting the live wires inside the finger of a rubber glove... Would that be a safe way to go, you think?

Oven still working - it's cooling as we speak. This is longest it's been running for ages, and I'm actually beginning to wonder whether the oven itself is fine by there may be a fault on the wiring. I say this because right now I've got a plug on the oven - in fact it's never blown a fuse on the plug, and it's only ever tripped when hard-wired to its own circuit. But the old oven never tripped the circuit, which is why I'm confused (as it makes me think the circuit must be ok). Is it possible the old oven managed to do some damage to that circuit when it originally failed?? Of is this maybe just coincidence while I work my way through the elements to see if I can find a faulty one...

 

[marconi]

Put the disconnected end inside a hard plastic bottle such as a small brown pill bottle - cut a small hole/slot in the cap for the wire to go through.

Post a picture of your consumer unit which clearly shows what circuit breaker supplies what.

Tell us please which circuit breaker is supplying the plug on the oven.

 

[gutted]

Images attached. The first shows the whole consumer unit, and the second is a close-up of the circuit which the oven keeps tripping.

When oven is causing the trip, the main breaker goes (as currently shown). I can leave oven (on the right) in off position and then throw the main switch and all is ok when there's no power to oven. The switch on right - so far as I know - goes directly to the main rocker switch for the oven (there's some very heavy duty flex then going between that rocker switch and the oven in question - when installed the oven is hard-wired, rather than on a plug; but it's on a plug now while I'm troubleshooting).

The 'cooker' labelled on that bank of three is for the hob - no problems with that. The 'sockets' labelled on that bank are for sockets near the hob (but nothing plugged in to them - we don't really use them; no reason other than placement isn't very useful).

In case you're curious, there's another 'oven' listed on one of the other circuits. That's for our main oven - the one I'm trying to fix is a combi microwave/oven/grill.
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Progress (we think). Working our way through, looks like maybe the top element is the culprit.

Bottom element - no apparent problems when up to 180 for about 20 mins.
Grill (only) element - no apparent problems when up to full temp for around 20 mins.

"Full surface area grill" (which is grill plus oven top element) trips out after a minute or so.

Previously the oven tripped when using "hot air" and "warming" functions, both of which I think use bottom element and top oven element.

Looks like I'll be changing the grill/top element unit... I'll keep you posted
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2nd time in a row - "full surface area grill" popped again. I'll try that again, but if it fails again then I'll go back to testing the other functions... If I can't get it to fail then it looks like it's definitely that top element.

 

[gutted]

Looks like we've pinpointed the culprit. With top element disconnected (and spade connectors taped up out of harms way) the oven doesn't trip anymore.

Previously it tripped - twice in a row - after only a min or so on "full surface area grill". But now? The centre grill still comes on as expected, but top element not connected and no trip.

Likewise it tripped using "hot air" (which is combination of bottom element and top element). With top element disconnected, it doesn't trip now.

(It also used to trip on other functions with top element, but I'm happy that I've narrowed it down now - oven is cooling and then I'll replace the top/grill element with the one from my old oven. Fingers crossed!)

 

[Taylortwocities]

British Gas engineer? Isn’t that a contradiction of terms?

 

[Lister1987]

As going to point to a DSES video doing an oven repair/fault find to help with how to approach it but you're sorted. Still a god watch mind you

View: https://m.youtube.com/watch?v=7azjwXNMa4w

 

[gutted]

There's an awful lot of back story involving BG. The engineer was a good guy, but the total faff in getting him onsite means that we've now cancelled our "Home Care" (or whatever) agreement.
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Cheers - will check out the video!

Meanwhile having changed the top element for my old one, all seems ok. It's still early days, but things are looking ok. It's not tripped out again yet, and we've used it to cook dinner so we're in good shape so far

 

[gutted]

That video is awesome ?

 

[Lister1987]

That video is awesome ?

No worries, once again @dseselectric and his random awesomeness helps another! David; do us a video on washing machine repairs and I'll be set for when the wife breaks the washing machine.

 

[telectrix]

No worries, once again @dseselectric and his random awesomeness helps another! David; do us a video on washing machine repairs and I'll be set for when the wife breaks the washing machine.

if she breaks it, buy her a dolly tub. then she'll be more careful about ramming stuff in till the door breaks.