Electrical fault query

[Andy Cap]

Forgive me if there's some pertinent fact missing here but the story's second-hand.

My BIL rang to ask why his toaster tripped the RCD in his new kitchen extension. All I could suggest was that there was an imbalance between L & N. He then went on to say that a while ago, when his wife used a mixer in the same socket, it blew the fuse in the spur unit feeding the extractor. Now I didn't understand this as I assumed there would be nothing connected on the L output side.

Anyhow, he had an electrician call today who stuck his tester in the socket and reported that the E was bad and simply tightened it up. When I ask what he had said about the spur unit fuse, he said that because of the earth fault, instead of the fuse in the mixer blowing, it blew the weakest point in the circuit !

I'm obviously being thick, because I don't understand any of this. Could someone possibly enlighten me?

TIA Andy C

[Andy Burns]

Quite likely; probably a build of of carbonised crumbs wedged between the element and the bread holding "cage". Tell him to take it outside, turn it upside down and shake it vigorously ...

[Andrew Gabriel]

It doesn't make any sense.

[Graham.]

My guess the electrician found no fault but pretended to find one to justify his call out charge, and make the customer feel it was worthwhile calling him.

He was asked a question about another matter and simply gave the answer he felt would sound plausible to them.

It was probably some debris as Andy said.

[ARW]

I agree.

However ring circuit continuity readings are needed. And ones that can prove the switched fused spurs in the kitchen are not switching the live cable on the ring.

[Fredxxx]

Can you confirm that when the fuse went, did the mixer stop? Is this socket off the same fuse as the extractor?

If the blown fuse had aged, it is possible, assuming that that fuse feeds both the extractor and the socket feeding the mixer.

I doubt it!

The tripped RCD is most likely down to crud in the toaster. As others have said take it outside and give it a good shake!

[Andy Cap]

Thanks gents.

I'm trying to get him to follow it up. Am I correct in saying that if the earth had been HR it would have made the RCD LESS likely to trip?

Andy C

[Dave Liquorice]

That is all you can say.

How is that particular socket wired? Is it via the spur unit fuse that is feeding the extractor? What are (were) the values of the fuses in the mixer plug top and spur unit?

[Andy Cap]

He's just told me that when the Extractor fuse blew, the mixer didn't stop, they simply heard it go pop ! As I understand it, the socket is on a ring and the Extractor is a spur from the oven feed.

I think the clagged up toaster probably explains the RCD issue but there's something else going on.

Andy C

[ARW]

If the resistance is less that 1667 ohms it would not matter.

The fault blowing the extractor needs checking (if indeed your B-i-L is correct).

It does sound like the electrician came out and could not find a fault.

[Andy Cap]

Thanks Adam, that's interesting to know.

He says that they heard the extractor fuse go pop but that the mixer didn't stop running. I'm inclined to leave him to it now and see if it happens again.

Andy C