RCD Tripping

[Andy S]

My RCD keeps tripping and I can't figure out why. But what I can do is reproduce it !

I've got a pond feature with the pump wired into a waterproof switch. The feed for the switch comes from a waterproof DP FCU. The feed from this is taken from a socket inside the house.

When I switch the pump on, everything works just nicely thank you. But as soon as I switch it off, it throws the RCD.

The RCD in question is on my consumer unit. It basically covers all but the lighting circuits.

I've unplugged all electrical appliances (in case of the cumulative leak issue) to eliminate that. I say all, I've not been able to disconnect the shower or oven. One thing to note, running off the FCU is another filter/pump. It needs to run constantly hence it not being on a switch (albeit the FCU has a switch on it which would be permanently on).

Any ideas why this might be happening?

I'd have thought you'd more likely to get a trip when turn an appliance on, not off !

Thanks, Andy

[Owain]

The switch is not disconnecting both poles simultaneously?

Owain

[dom]

If you're switching an inductive load -> more arcing on switch-off

->more spikes on the mains (both live and neutral) that will be passed to earth via any mains spike filters (possibly before mains switches) still connected anywhere on the RCD protected circuit.

[Andy S]

[Owain]

Replace with DP switch and don't top post?

Owain

[meow2222]

a common cause of this is leakage on the neutral side. As the switch opens, briefly 240v goes on to the usually neutral line, so leakagae i goes way up and trips the rcd. In your case it'd be something after the switch, ie the pump or its wiring.

NT