RCD nuisance tripping headscratcher.

[dtec dave]

I have been out to a nuisance tripping RCD this morning, there are 3 socket circuits, 1 boiler circuit, and 1 oven circuit protected by the RCD.

I started by checking the IR between L-E and N-E, the reading was between 2 and 3 M ohms on every circuit and leg.

I then disconnected the CPCs for each circuit in turn and I was still getting between 2 and 3 M ohms between L and the earth bar.

I disconnected all the CPCs and was getting varying readings between the lives and CPCs of the other circuits.

I was also getting varying voltages between the L and CPC's even when the RCD was turned off.

I was also getting various voltages between the different CPCs

Can anyone explain what would cause this?

Cheers

 

[UNG]

I have been out to a nuisance tripping RCD this morning, there are 3 socket circuits, 1 boiler circuit, and 1 oven circuit protected by the RCD.

I started by checking the IR between L-E and N-E, the reading was between 2 and 3 M ohms on every circuit and leg.

I then disconnected the CPCs for each circuit in turn and I was still getting between 2 and 3 M ohms between L and the earth bar.

I disconnected all the CPCs and was getting varying readings between the lives and CPCs of the other circuits.

I was also getting varying voltages between the L and CPC's even when the RCD was turned off.

I was also getting various voltages between the different CPCs

Can anyone explain what would cause this?

Cheers

Have you done any tests on the RCD or checked what leakage currents are present

 

[dtec dave]

Have you done any tests on the RCD or checked what leakage currents are present

 

[dtec dave]

Have done all the RCD testing..passed ok.

I'll get myself a earth leakage clamp meter if that's the only way of finding this fault.

 

[buzzlightyear]

I'll get myself a earth leakage clamp meter if that's the only way of finding this fault

ramp test it .

 

[Wilko]

I disconnected all the CPCs and was getting varying readings between the lives and CPCs of the other circuits.

Hi - fwiw, I think these various voltages are induced. The proximity of the floating conductor to an L will induce a voltage in the floating conductor. This is normal and it’s reason to tie all unused conductors to ground.

 

[Wilko]

Smee Again - word of caution when IR testing a circuit with the boiler - make sure the boiler is DP isolated before starting. Some boiler control boards “don't like it up em”.