The resistance of a slug ins under 8kohms...

[Vir Campestris]

How do I know this you say? Well, 8k is 30mA at 240V.

We were watching the news last night, when the TV and the lights went off. It didn't take very long for me to realise that the landing light was still on. We have a split board with 2 RCDs, and upstairs is sensibly on the other half. A little playing, and I had the fault down to the breaker marked "ring main". A bit more playing - and I had unplugged everything in the house. And still I couldn't reset the breaker without the RCD going off again. So I went to bed, and called a sparky in the morning (I know, but I had to go to work).

He traced the fault with some sort of gadget well enough to get the right socket first time. We recently had an outside cable installed to feed a pond pump, and inside the backbox was a bit of a mess. It looks as though slugs have been crawling up the cable and using it as a house. Until one touched the wrong bit.

Sparky says he's seen all sorts of faults, but that's a new one!

Andy

[Mike Barnes]

I had the same problem with a spider, which I found through trial and error. I don't know how it got in there, unless it squeezed in when it was a lot smaller and somehow managed to thrive in there.

[Graham.]

I had a similar fault some years ago caused by ants. I found several of them fused together in an arch between the live and earth terminals in the wiring centre of my central heating.

[Bill Wright]

I had exactly the same thing, except they went up the cavity and found a hole (that shouldn't have been there) that led to some dado trunking with sockets fixed along it.

Bill

[Dave Plowman (News)]

Outside circuits like this should really have their own RCD.

[Brian-Gaff]

Well yes, animals tend to cause issues don't they. The old chewed cable down the garden is quite common which is why many have that on a separate breaker of course. However when I was working in the 60s doing repairs on pcbs sent back from tv rental companies, I encountered many fried insects, usually spiders on pcbs. Whether said insects were the cause of the fault or collateral damage, as we say today, is never that clear though.

Brian

[Andrew Gabriel]

I got parents' desk fan out of the loft at the beginning of the summer and left it for them to use if they needed it. Later I hear it tripped the ring circuit. Quickly established it was due to earth leakage (RCBO), which was a first for me on a two-core double-insulated plastic cased appliance. I opened the plug, and there was a spider's web bridging the pins. Spider was not there and presumably left long before this happened. I had always thought that webs were insulators - silk was used as an insulator long ago. Cleared the web out and it was then fine.

[ARW]

Agreed. However you do know how difficult and expensive that could be when working in some houses.

What is missing is a double pole isolator for the outside electrics next to the socket the power was taken from.

[Dave Plowman (News)]

I fitted a local RCD (a spur unit) for an outside socket at the front door before changing the CU to a split type with RCDs.

And it does seem to trip before the CU one. On the very rare occasion this has happened.

Yes - although most spur units are 2 pole these days?

[Tough Guy no. 1265]

I had one inside the washing machine do that. It just evaporated and made a smell. But then I don't have namby pamby earth leakage breakers.

[Bill Wright]

Mine did.

Bill

[Brian-Gaff]

How are they with brass and aluminium? Brian

[ARW]

I believe that it is good luck on which RCD trips first - TBH usually both trip.

Yes - all "switched" fused spurs are all double pole. I was not suggesting otherwise, just pointing out that I often just use a double pole switch in preference to a fused switch.

As you can appreciate my work sometimes has to be a compromise between the best available and the bare minimum depending what the customer wants or can afford.

eg Ideally I would put outside lights on their own RCBO, however a good comprimise is to use a double pole lightswitch for the outside lights and then power them from a local lighting circuit. If water does get into the outside light then the homeowner can isolate that outside light and restore power to the rest of the lights and anything else sharing that RCD. Such an installation costs less than £2 per outside light switch.

[Vir Campestris]

Missing from the description only.

We have a double socket and two fused isolators next to each other. One isolator is for planned future expansion.

Andy

[Vir Campestris]

Leakage on PC PSUs is common as anything. But on an earthless device - where is it leaking to? Surely you'd notice 30mA?

Andy

[Andrew Gabriel]

Inside the plug, between live and earth (or possibly neutral and earth, but I doubt it in the case of a spider's web).

[Vir Campestris]

Ah, silly me, I assumed it was one of these plastic earth pin things.

Andy