New electric cooker causing power to trip at fuse. The fuse is reluctant to flick back on after.

[Stephen]

Hi all.

Thank you all in advance for your help and advice.

I was hoping to get some help and advice on a cooker issue I'm experiencing.

My cooker is "brand new" and I recently had it installed by my father inlaw (competent tradesman although not an electrician)

The cooker is brand new but actually 3 years old... this is because it's an ex display oven from a hardware store (wife works there)

The Cooker will work fine for 20 uses. No issues whatsoever.

But we have had 4 occasions where we haven't been able to use it.

What was happening was we would turn the cooker on and it would trip 10 seconds later. Then we would put power back on then try again and it would trip 4 or 5 times before we sack it off for beans on toast.

We were not using the hob at the same time.

I will also add that when it happened last time the fuse wouldn't come back on. In fact most.times It trips for this reason I have to flick the fuse up multiple times.... that's another point it doesn't trip the rcd it trips everything at the fuse

I found one website that suggested the fuse not wanting to come back on can suggest an earth fault.

I was thinking maybe the wiring came loose in the back of the oven or the sockets maybe.

It can't be the element cause it will work for 20 times on full load with not a single issue and the fact it's brand new really.

I can't see it being an element issue but I'm hoping a knowlegable electrician may have an idea or a way to eliminate possibilities.

The key points are

• I can use the cooker most of the time
• It mostly trips immediately but can be 90 seconds after powering up
• I am not running anything at the same time
• The power trips to the whole house but the fuse board where it is on a separate fuse remains in the "on" position when it trips the electricity.
• When I try and flick the power back on at the fuse I sometimes have to do it 6 or 7 times for it to actually come back on.
• The old cooker never did this so the mains wiring can't be faulty surely.

I really appreciate any help. I am able to use it now but I did trip the power when I first turned it on tonight.

Thank you all in advance and apologies of this isn't the right forum.

Cooker is an AEG competence double oven.

Stephen

 

[Deleted member 9648]

It's a TT, the upfront RCD is a relic of the previous DB

 

[SparkyChick]

Ok well there is something else. The old isolation switch before remodelling was a huge external patress box on the wall the other side of the kitchen.

In order to "extend" the existing wiring from that location to the new isolation sockets and then the cooker a large junction box was buried into the wall which was then plastered over.

Who did the kitchen wiring? Did you get a certificate for it?

Can you remember where that junction box is?

 

[Stephen]

You need to have ALL circuits IR tested by an electrician, the cooker may be a red herring as if there is a N-E fault anywhere on your installation this can cause tripping only when a heavy load (such as your cooker) is on, misleading the uninitiated to assume the cooker is at fault. Of course it could be the cooker, but I recently attended a tripping fault where a perfectly good shower had been replaced because it only tripped when the shower was on.....and continued to trip when the new shower was used. Fault was on an outside light.

I will add we use a power shower which doesnt cause this to trip.... what would prevent this Crabtree rcd from flicking back on?

As I discussed in my OP when it trips this RCD is reluctant to trip back on.... takes sometimes 8 or more attempts. Wondered if you knew?

 

[Stephen]

You need to have ALL circuits IR tested by an electrician, the cooker may be a red herring as if there is a N-E fault anywhere on your installation this can cause tripping only when a heavy load (such as your cooker) is on, misleading the uninitiated to assume the cooker is at fault. Of course it could be the cooker, but I recently attended a tripping fault where a perfectly good shower had been replaced because it only tripped when the shower was on.....and continued to trip when the new shower was used. Fault was on an outside light.

I will add we use a power shower which doesnt cause this to trip.... what would prevent this Crabtree rcd from flicking back on?

As I discussed in my OP when it trips this RCD is reluctant to trip back on.... takes sometimes 8 or more attempts. Wondered if you knew?

How was the connections in that junction box terminated? Screwed? MF?

Yes screwed... it was a large round junction box... I can find a url for it from toolstation if needed?

 

[Deleted member 9648]

I will add we use a power shower which doesnt cause this to trip.... what would prevent this Crabtree rcd from flicking back on?

As I discussed in my OP when it trips this RCD is reluctant to trip back on.... takes sometimes 8 or more attempts. Wondered if you knew?

A power shower is a relatively light load compared to a cooker, it's sounding more and more like a N-E fault, not necessarily on the cooker

 

[SparkyChick]

I will add we use a power shower which doesnt cause this to trip.... what would prevent this Crabtree rcd from flicking back on?

As I discussed in my OP when it trips this RCD is reluctant to trip back on.... takes sometimes 8 or more attempts. Wondered if you knew?

When it trips, do you leave everything on and just turn it back on?

If so, the next time it trips, turn everything off in the fuse box except the RCDs, turn the big RCD that trips back on and then turn them back on one at a time... do the cooker last.

It's possible the fault is in the element and as it cools down it goes away and allows you to reset the RCD, but following this procedure above should (if the fault is only on the cooker) allow you to get the power back on quicker.

You shouldn't really keep turning it on under load either as it will damage the contacts.

 

[Stephen]

Who did the kitchen wiring? Did you get a certificate for it?

Can you remember where that junction box is?

No other wiring was touched.... just extended original installation so we can move the isolation sockets.

I can remember where the junction box is buried but has been freshly decorated over.

 

[Stephen]

Who did the kitchen wiring? Did you get a certificate for it?

Can you remember where that junction box is?

And no certificate

 

[SparkyChick]

No other wiring was touched.... just extended original installation so we can move the isolation sockets.

I can remember where the junction box is buried but has been freshly decorated over.

Well I hate to break it to you, but you may need to do a bit of touching up as the fault could be in there.

You're going to need the assistance of a local spark with appropriate test gear I think.

 

['mr2'gd4u]

I will add we use a power shower which doesnt cause this to trip.... what would prevent this Crabtree rcd from flicking back on?

As I discussed in my OP when it trips this RCD is reluctant to trip back on.... takes sometimes 8 or more attempts. Wondered if you knew?

Yes screwed... it was a large round junction box... I can find a url for it from toolstation if needed?

If if buried 8t needs to be maintainence free.

 

[Stephen]

When it trips, do you leave everything on and just turn it back on?

If so, the next time it trips, turn everything off in the fuse box except the RCDs, turn the big RCD that trips back on and then turn them back on one at a time... do the cooker last.

It's possible the fault is in the element and as it cools down it goes away and allows you to reset the RCD, but following this procedure above should (if the fault is only on the cooker) allow you to get the power back on quicker.

You shouldn't really keep turning it on under load either as it will damage the contacts.

I will do that and I agree it isn't ideal.

The cooker rarely gets up to temperature when it trips.

Also I have used the cooker for 10 days with no trips.... seems sporadic.

 

[SparkyChick]

I will do that and I agree it isn't ideal.

The cooker rarely gets up to temperature when it trips.

Also I have used the cooker for 10 days with no trips.... seems sporadic.

It's not just faults that can trip RCDs. It could be cumulative leakage, where under a certain set of circumstances there is over 30mA of leakage, could be sometimes there is leakage in the junction box and others not.

Loose connections can also trip RCDs.

 

[123]

Out of interest, who did the works to extend the cooker circuit and put that junction box in the wall?

 

[Stephen]

It's a TT, the upfront RCD is a relic of the previous DB

Hi what do you mean my this please? I tried googling the acronyms to no joy. Appreciate your help

 

[Stephen]

Out of interest, who did the works to extend the cooker circuit and put that junction box in the wall?

My father in law.

Very competent although admittedly not a trained electrician.

Thanks