MK versus Contactum

[Careful_Bodger]

Trying to help out a mate with a nuisance tripping problem.....

Would an MK 80A 30mA RCD be less susceptible to tripping than a Contactum 80A 30mA type ?

Is the ~£20 lower price tag for the Contactum part indicative of design/build quality?

(Background: a temporary install with a loaned MK RCD doesn't trip under the same conditions which would otherwise trip the Contactum)

Any help (or flaming) appreciated.......

 

[Darkness]

I have a CU with Contactum mcb's and they may be cheaper but on performace they do their job very well.

A sparky with use of both will give you the help you need.

What sort of conditions are you using to trip both?

 

[Careful_Bodger]

Thanks Dar,

'snot my CU but I am told that the problem RCD is on the socket side (in the normal way) but, among other things, switching on the lighting side causes the tripping.

I think it could be that the original RCD is faulty...... but there is that huge price difference.

Does this help?

 

[securespark]

If switching on the lighting causes tripping, and your lighting is NOT connected on the RCD side, then you have the lighting neutral on the WRONG block.

Double check ALL wiring to make sure that the neutrals are all in their respective places, IE RCD protected circuits are wired to the neutral block fed via the RCD and non-protected circuits are wired to the neutral block fed direct from the isolator.

 

[Careful_Bodger]

Thanks SS,

Would your suggestion hold given that the MK does NOT trip under the same conditions?

Ta.

 

[Damocles]

Manufacturing spec on all 30 mA RCD is supposed to be that they will not trip at 15mA but must trip at 30mA leakage. So it is possible that a small leakage might trip one good one but not trip another. If one of them trips on anything turned on but the other does not trip, then it suggests one is faulty.

Any chance of a loose wire or something which altered when you swapped the RCDs?

The manufacturing spec is a british standard. Reliability might be different for different brands. Different brands might be made by the same company or under licence to the same design.

Like the man said, if non-RCD circuits are causing tripping suspect a wiring problem.

 

[andy]

Thanks SS,

Would your suggestion hold given that the MK does NOT trip under the same conditions?

Ta.

if the neutral is wired in the wrong place form the lights, a 100w bulb will allow 400ma (approx) extra thru the RCD, so every type will blow (since itz way above 30ma)

 

[Damocles]

Beg pardon. I was thinking of a N-E short. A N-E short on a protected circuit could still cause a trip if current is drawn on the non RCD side. Only part of the current is going to to earth, so fault current is only a fraction of load current. What fraction depends on where the short is. So some loads might be below the 30mA threshold.