Fault finding a tripping RCBO

[Tim Lamb]

In message , "Dave Plowman (News)" writes

Door bell transformer?

>

[Tim+]

Security light? Aerial amplifier?

Tim

[Bill]

In message , "Dave Plowman (News)" writes

Once you have either found or discounted all the reasonable ideas at this time of year maybe a dead mouse or rat that had chewed a cable; although your resistance readings seem a bit low for that. The body would still take out an RCBO for a while until it had thoroughly dried out though.

[Mike Tomlinson]

En el artículo , Chris French escribió:

I know the feeling :)

That could be ok. It depends what is (still) connected/plugged in to the ring. Try and ensure everything is completely unplugged, not just switched off at the socket.

Both too low.

You /have/ separated out all 6 wires at the CU end, haven't you?

It'd be interesting to know what you find. I'd be thinking in terms of a screw or nail through a cable which has finally worn away the insulation (e.g. due to movement of floorboards), water in external lighting, a dead rat gently sizzling away somewhere underfloor, an element in a kettle/dishwasher/washing machine etc. breaking down, etc.

Of course, it's Christmas. Stuff like this always happens at Christmas!

Hope you sort it soon.

[Chris French]

In message , Mike Tomlinson writes

Everything is unplugged , fuses for a couple of FCU's removed (outside light and pond pump)

Yes, there are all sorts of things it might be, but it's not so much the fault itself that is exercising me - sooner or later I'll find it. It's that having apparently split the ring, both legs were still tripping. So this has made fault finding more awkward. I can only think that the ring has been wired incorrectly, separate from the tripping fault. There is a section of ring that is more recent in the kitchen. I'm suspecting that were that joins into the original ring might be the location. Of course that appears to be under the floor in the spare bedroom, which is full of clutter.....

So after changing tack, I've been working my way from the CU tracking cable runs and trying to isolate the section with the fault. So I now the legs of the ring are forming two radials, each on it's own RCBO. both those sections are fine, I've just got a bit in the middle were the problem lies.

[Bill]

In message , Chris French writes

Simply removing the fuses is not enough if you have a N-E problem, which can also trip an RCBO, as this only disconnect the Live.

[Chris French]

In message , Bill writes

I guess not.

anyway, doesn't matter in this case as they are on a bit of the circuit which is now working fine.

however, mucho frustrated at the moment, as I've spent ages rootling about, pulling up floor boards etc. I still can't trace all the cables particularly where some of the more recent sockets connect up to the original circuit and where the fault seems to lie somewhere..

It's the sockets which feed the dishwasher, fridge and microwave so can't easily just ignore them for bit .

[Chris French]

In message , Chris French writes

Well, I think I'm calling it quits for now. The first Christmas rellies arrive on Tuesday evening and there is much to do. I'll come back to after Xmas.

I've got 2 radials circuits now which are fine. All the sockets and other stuff on them checked out ok, except for a loose live pair in one, but no sign of overheating with them. but if I connect up either end of the radials to the reaming section of ring then it trips. But I still can't trace all this run. And I don't want to pull up more floorboards or pull apart anymore of the kitchen.

Ought to swap the 32A RCBO's for 20A though I guess

The kitchen installers have form for crap wiring. They connected a socket above the worktop and the gas hob supply to an old socket in an alcove behind the kitchen cupboards, down by the floor. Discovered when the socket developed a live-earth fault and the gas hob became live (this was before the CU was replaced).

So who knows where they might have hidden a connection?

[Andy Burns]

Here's the extreme method!