Rcd

[Bazspark]

When visiting relatives house she mentioned RCD was tripping sometimes and would i take a look. MEM split board and had no tools so i got on chair pressed trip button and no trip, told her trip was probably faulty and would replace. Returned another day with few tools in car and replaced trip. pressed test buton and still no trip so i put rcd tester on it and all fine, checked polarity with independant earth and all fine, house is TT system and trip is 30mA feeding shower, garage and sockets. also checked house earth spike and it was fine also. didnt have a lot of time to investigate further as it was also family visit but find it hard to believe that 2 trips had faulty trip button and when i simulated trip with bypass between neutral and earth trip functioned. anyone got any thoughts

 

[baldsparkies]

Just popped home for a cuppa, anyway sounds like your only problem is with functional testing of the RCD all else is ok. (Is that right)

If so I would follow the advice of previous posts regarding changing the RCD again. As said, its not immpossible for the new unit to be faulty.

Remember the test button generates an inbalance through the coil using a line resistor, that generates an eddie current in the relays secondary winding and the generated voltage differance operates the relay, with this in mind have you checked the mains voltage under load ? Also dont forget to check your tripping times on both ends of the waveform ie 0 degrees and 180.

It doesn't sound like a low neutral to earth resistance otherwise the rcd would be nuisance tripping, or crossed neutrals at the neutral bar. That would cause tripping the moment the offending circuits were energised.
Hope this info helps

 

[Bazspark]

I am going to change the trip again, thanks for input every one, I think my problem is myself refusing to believe two trips could be faulty and was hoping someone could give me a easy answer to save me having to change again. Will keep you all posted

 

[spadxiii1918]

Does the MEM have a Functional earth cable?
The test button is usually a mechanical operation and shorts out as you described earlier. Could be faulty.

 

[kung]

How long has the fault been there ? did they have any work done just before it started or got a new bit of equip ? might be worth a check. All you can do is do tests/checks if all ok as said prob a faulty rcd although does sound strange that one.
Regards
Kung.

 

[Bazspark]

Does the MEM have a Functional earth cable?
The test button is usually a mechanical operation and shorts out as you described earlier. Could be faulty.

Yes the MEM trip had a functional earth cable which was properly connected to earth busbar and I have had some problems before with MEM trips which was why I thought it was the problem. The new trip I installed was a Hager and they have never given me any problems. Have not had a chance to revisit house yet but apparently New trip is not given nuisense tripping since but test button still not working. No new equipment in house and problem started about 3 months ago