Cooker hood trips other circuits on fuse board: what's going on?

[Tom Oxford]

Hi,
I am a newbie to this site, not an electrician but looking or advice. Please excuse any incorrect electrical language: I'll do my best to describe our strange electrical problem.

Sometimes when we are cooking, the fuses for downstairs & upstairs sockets (2 circuits) trip. It's when we use the hob and I'm pretty sure it's the cooker hood (as in the extractor fan) that is causing the problem. The other day a friend turned on the fan and the circuits tripped, without the hob being on. That said, there is a strange phenomenon whereby other kitchen appliances (hood, dishwasher, microwave) when switching on can cause the ignition to spark on the hob, so I feel something odd is going on with the hob too.

The kitchen was installed a year or two after we had the house mostly rewired, and the appliances and sockets in the kitchen have their own circuit. We have had three electricians look at these issues, all doing thorough testing, and none could come up with an answer. The sparking hob is just odd, the fan tripping independent circuits is more disturbing to me. In practice it's just a nuisance (losing internet connection because there's no power to the router, resetting the bedroom clock every time it trips), but I'm always nervous when there's an unexplained electrical issue. Why is an appliance tripping circuits that are totally independent?

Any thoughts, anyone?

 

[SparkyChick]

First off, can you post a picture of the front of your consumer unit showing which fuses/breakers trip and when?

This may help as sometimes it's not a fuse, but another protective device.

 

[JohnnyRingmain]

Ignore me.

 

[D00DY_T00DY]

I've had it before where the factory molded plug was at fault.
Just a thought

 

[Octopus]

Did any of the sparks clamp the tails to measure the earth leakage?

I'm guessing it's the RCD which is tripping!

 

[Pete999]

Is it a circuit breaker that's tripping, or the RCD prior to all your cbs?

 

[SparkyChick]

Did any of the sparks clamp the tails to measure the earth leakage?

I'm guessing it's the RCD which is tripping!

Is it a circuit breaker that's tripping, or the RCD prior to all your cbs?

We're all thinking along the same lines

So which do we apply.... great minds or idiots

 

[telectrix]

just consulting the tea leaves. might be a while as i don't drink tea, just beer.

 

[Pete999]

We're all thinking along the same lines

So which do we apply.... great minds or idiots

Someone get some beer delivered to Tel's Gaff

 

[Tom Oxford]

First off, can you post a picture of the front of your consumer unit showing which fuses/breakers trip and when?

This may help as sometimes it's not a fuse, but another protective device.

Here's a picture of what I think of as the main board, which I think is what you mean by consumer unit. Is this what other folks mean by RCD? It's

First off, can you post a picture of the front of your consumer unit showing which fuses/breakers trip and when?

This may help as sometimes it's not a fuse, but another protective device.

2nd attempt at replying - hope the server doesn't crash this time... Here's a picture of what I think of as the main board, which is what I hope you mean by consumer unit. I did say I wasn't an electrician It's fuses 5 & 6 which are tripping, when the extractor fan is turned on (but not every time).

View attachment 36063

 

[Tom Oxford]

Did any of the sparks clamp the tails to measure the earth leakage?

I'm guessing it's the RCD which is tripping!

I don't remember being told my tails were being clamped, sorry...

When you say the RCD might be tripping, do you mean there's a fault within the main board? I'm afraid I know very little about electrics so you'll have to explain things in really simple terms...

 

[Tom Oxford]

Is it a circuit breaker that's tripping, or the RCD prior to all your cbs?

I don't know how to answer this. The two switches on the consumer unit flick off (see photo in my other reply).

 

[telectrix]

deleted

 

[Midwest]

Think they might be RCBO's, might be wrong

 

[SparkyChick]

You appear to have RCBOs... these are a combination of MCB (miniature circuit breaker, which protects the cables of the installation against over current - preventing the cables from getting hot and potentially catching fire etc.) and an RCD (Residual current device, which detects current leaking from the circuit, typically through the earth and cuts the power when this leakage is above a predetermined level - for domestic use, this is typically 30mA).

Based on the fact that turning something on on one circuit trips two circuits, you could have a situation referred to as a borrowed neutral, when the neutral wire from one circuit is actually used for another circuit which has it's own live feed. In this case, the current flowing out of one RCBO won't be the same as is coming back into it (it will trip) and the current flowing into another won't be the same as is going out (it will also trip).

I'd also be looking to rule out a neutral-earth fault (where there is an unwanted connection between the neutral wire and the earth wire).

These two issues at least could cause two circuits to trip at the same time.

I'm assuming by the fact that you mention the kitchen has been worked on, the problems started after that? If not, when did they start and had you had anything done immediately before that?

Is this totally repeatable? i.e. does the fault occur every time you turn on the extractor?

You say you've had a number of electricians look at it. Were they all registered with competent persons schemes such as NICEIC, NAPIT? You can check here:- Home - http://www.electricalcompetentperson.co.uk/

I think others will agree when I say, you need to find yourself a decent spark. I'd start by taking a look at the member directory here.