Nuisance tripping has stumped our sparky...

He's spent four hours testing, but still hasn't tested the cooker or boiler circuits ... and he's "stumped" :confused:
 
As said some faults are hard to find, there are some appliances which are known for problems with fault finding, the frost free freezer being one, they have a defrost heater which is often a mineral insulated cable type so can absorb water, but it only comes on a couple of times a day, so a fault caused by the freezer may only trip the RCD once or twice a day. Often only the line is switched so it can be tested on the neutral, so to test means isolating line and neutral from supply and testing mainly the neutral rather than line. However if double pole switched then only way is to swap which RCD supplies the freezer, or fridge/freezer. But most refrigeration units are very voltage sensitive so keep any extension leads as short as you can.

To my mind the nail rings alarm bells, it would seem it is likely that has some bearing on the problem. Clearly this needs the electrician, but swapping circuits from one MCB to the other can help isolate what circuits you are looking at. Swapping the socket circuit would be the first I would look at, if at least you know it the fault is on that circuit then you know where to look. Also the cooker is another appliance well known for leakage again due to use of mineral insulated heaters so swapping that circuit will also help isolating what is causing the problem.

We read trade papers and the like about accidents, this report on the death of Emma Shaw shows us how easy it is for a cable to be damaged and the fault to show its self quite a distance from the actual fault, at least you have RCD protection so what happened to Emma Shaw will not happen to you. But that nail would worry me. I would want to dig a lot deeper into why he got those readings than you relate to here.

Also as said fault finding and installation are a world apart, he may be a really good installation electrician, but not that good at fault finding, both myself and my son would often collaborate on fault finding, two heads are better than one. Not that either of us were better than other just two people can often find faults better than one. Daughters house it was a socket and the neutral wire had been caught by a screw holding socket, it was intermittent, and since on neutral only tripped when there was a load. Faults like that are hard to find.

The other way is to replace the RCD with RCBO's that means when it trips you know which circuit, and it does not effect other circuits.
 
Maybe he is more of a cable installer and less of an electrician. Four hours is a long time to do insulation resistance testing on a large domestic installation.
 
bernardgreen said:
Maybe he is more of a cable installer and less of an electrician. Four hours is a long time to do insulation resistance testing on a large domestic installation.
Click to expand...

He never said he was IR testing for 4 hours to be fair, when I found the leaky pipe problem it took 2 visits including partial dismantling of a fitted bedroom to locate it
 
I agree, four hours isn't necessarily a long time, just puzzled why he didn't continue and test the cooker and boiler circuits.
 
We had our boiler replaced on Monday (by SHL, whom we believe are a big and reputable company). Since then, it was initially tripping even more often -- literally, as they were packing up their kit. We decided to go camping from Tuesday to today, partly due to the nice weather but also to get away from the tripping. The only thing we learned was that the boiler isn't earthed (I don't know if this is relevant). The boiler company aren't able to send their electrician to finalise installation of the boiler until the 30th, but they assured us that it would still work (obviously it can't work if the RCD is tripping!).

We've come back today. I had a bath, after a couple of tripping episodes. After that, my husband attempted to run hot water (this was about 2 hours ago). Now we can't get the RCD to stay up AT ALL. (At least only one of us smells!)

We have just removed literally every plug from every socket, even those we have on the other circuit, just in case, as well as removing the fuses from the cooker hood, oven element and boiler. It's still staying tripped!

We have the electrician coming out AGAIN tomorrow. My husband thinks I have gone mad because I'm on about electrocuted slugs being the cause...

Thanks so much for replies. Fingers crossed it'll be sorted tomorrow... Having to go to relatives' house to have a shower!
 
The only other random fact is that, the very first time the RCD tripped, I happened to visit a takeaway. Making conversation, the server asked if our electrics had also gone off that day; apparently, it had gone off for quite a few houses in the area.
 
I doubt it will be anything to do with that. A boiler ought to be supplied via a fused spur unit (usually double poled), try switching that off and resetting the RCD.
 
An RCD not staying "in" is an electricians god send. You know you're going to find a reading you can chase.

It's intermittent faults that can be tricky.

Even a dumb spark should be able to trace a fault if the RCD won't hold at all!
 
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