How likely is a faulty RCD?

[DCC]

Been trying to track down the cause of one of my RCDs tripping, I've pretty much worked out which combinations of devices can cause it to trip - big contributors washing machine, hob, microwave, underfloor heating and the server/routers combo in my understairs cupboard - I can get it into a stable state and power up one more thing and *pop* there it goes again. Can't tell what the fridge freezer is contributing as its not easy to make it do what you want.

Now its possible that one of those is contributing 90% of any leakage or they could all be doing a bit - thing is, everything was fine until a couple of weeks ago, no trips at all since the CU was changed about 14 months ago.

Realistically how likely is it that the RCD could be at fault? The impression I have is that they are pretty reliable?

Almost tempted to spend some cash on that earth leakage clamp meter someone linked the other day to see whats really going on.

 

[Chri5]

If the board is a dual RCD why not just swap them over and see if the naughty RCD plays up on the other rail.

 

[Taylortwocities]

Do you have any nice new meaty TVs on that circuit, or a few bits of computer equipment?
They have mains filters on them that can add up to enough to trip an RCD.

Its best to test things rather than try and guess what could be the problem. Borrow an RCD tester and see if your RCD is out of spec.

 

[Lectrician]

A neutral to earth fault of some impedance will cause an RCD to trip as you start to increase the loading until a certain point is met. In my experience, this is where the majority of RCD related faults lie.

It could also be that you simply have a lot of leaky items, each contributing.

You need a spark who has an insulation resistance tester (all should!), and a spark who knows how to use one and interpret the results accordingly!

 

[DCC]

All good suggestions.

Sadly no new meaty TV, the old one is still going strong and I can't justify replacing it! I may be able to get hold of an RCD tester but as Chris says swapping the RCDs over would be a simple test - except its a good feeling having a properly fitted CU that I've never played with (unlike its predecessor!). All wiring was IR tested when the CU was changed last year but that doesn't say anything about its state now I guess.

This is all a minefield that will only get worse with the new regs...

 

[mointainwalker]

I used to supply components to one of the largest European RCD manufacturers, and they always used to tell me that their point of view was

" It may not have to be activated once in twenty years, but when it needs to, it has to work "

THeir production facilities , wth full "clean-rooms" and all other QC measures were extremely impressive.

IMO failure from a major brand very unlikely.

 

[DCC]

Well the cause and the solution became clear a few days before christmas - remember kids, underfloor electric heating and leaking washing machines dont mix.

Oh well, it'll dry out sooner or later