RCD Tripping

pdewfall · Posted: Sun Jan 21, 2007 2:52 pm Post Subject: RCD Tripping

Hi I've got a bit of a problem regarding the RCD tripping and nothing else when the central heating switches itself off. It is currently intermittent, have you got any thoughts?

Regards,
Paul

jj4091 · Posted: Sun Jan 21, 2007 2:58 pm Post Subject:

Do you mean the rcd trips but the mcb does not? Do you have the tools to test with?Is the heating spurred off the ring main?

pdewfall · Posted: Sun Jan 21, 2007 3:07 pm Post Subject: RCD Tripping

Yes the RCD trips but none of the MCD's trip. I'm not an electrician so I've not got the tools with me. British Gas recently replaced the thermostat and have replaced the central heating programmer. With the problem still happening. I was just trying to rule the circuit breaker out before going any further. I believe that the heating is spurred off the main ring.

dingbat · Posted: Sun Jan 21, 2007 7:03 pm Post Subject:

Spurs for fixed equipment from RCD protected socket-outlet circuits... there's your problem. Asking for trouble...

solair · Posted: Mon Jan 22, 2007 11:27 am Post Subject:

Something in your heating system's clearly faulty. It could be a leaky pipe that's dripping water onto a pump or motorised valve or something.

Basically, it's picking up current flowing to earth.

Get the installer back to sort it out.

RCDs will blow if there's a leakage to earth, usually anything over 30mA. They're designed to prevent electric shock

MCBs will blow if a circuit's overloaded. e.g. at 6A, 10A 16A, 20A, 32A, 45A, 63A etc. as per their rating. They're designed to prevent fire due to overloaded cables.

If you've a short circuit to earth, the RCD will trip almost instantly and your MCBs will remain on.
If it's a short circuit between L and N or an overloaded circuit the MCBs will pick trip.