RCD tripping

[DGF]

Hi All

New to the forum and just passed 2330 and 2391 with an expensive test meter on its way!!!

the first thing on my list is a mates RCD tripping - funny how many mates you find suddenly ??!!!

My plan is to first test the RCD but would be surprised if this was the problem, then I would go for IR test on the individual circuits ??

I am thinking a joined Phase/N to cpc would be no good in this case so should I go for the 250V soft test first then go with the full 500V on P-N, P-E, N-E

Sorry for the "basic" question but rather look a tool in the forum than round at his house !!

cheers

Don

 

[Richard Burns]

Try and diagnose the fault first.
When does it trip? Is it at the same time each day, was anything specific on at the time?
Does the RCD reset at once or do you need to turn off breakers first?
Remember it could be an appliance fault and not just the fixed wiring (which is normally fairly stable)
Intermittent faults are a nuisance to find.
Permanent ones should be quick (N-E fault if it doesnt clear on switching off breaker or L-E fault if it does).

Similar times are for timed things like heating controls, random times with no one at home is automatic things like fridges and freezers. When someone is home were they turning on anything at the time or walking anywhere in particular that may have a damaged cable under it.
Which circuits are tripping?
Has there been any work done of any kind DIY or professional?

This should allow you to narrow things down slightly, with luck and then you should assess the affected circuits for obvious faults, loose damaged accessories, outside lights full of rain?

Then test RCD.
Then see if you can recreate the fault if at all possible so that you can then switch off breakers to narrow down to the circuit (if L-E) or remove neutrals (if N-E).

L+N to E may well allow you to identify the specific circuit and then it gets fun as you remove all loads and test L-E and N-E and start to break the circuit down to narrow the fault to a point or junction box.

Could be quick could be slow but good practice.

 

[Deleted member 9648]

Good advice from Richard,
The only way I differ from the majority on here is that when I have a tripping RCD...intermittent or otherwise... my first step is always a global IR test on the fixed wiring......I've had many occasions when other electricians have 'cured' the fault by relacing RCD's after apparently unsatisfactory ramp tests....or disconnecting suspect appliances etc etc,only for the fault to continue after they've left,usually a fault on the fixed wiring shows up and would have done all along if they'd bothered to test. Eliminate that first before looking elsewhere.

 

[Dolman100]

could you please explain how to perform a "global IR test"?

 

[SirKit Breaker]

could you please explain how to perform a "global IR test"?

Isolate the supply, join live and neutral together on load side, and IR test between joined L and N to earth.

Cheers.........Howard

PS GN3 explains it better, and it is illustrated.

 

[ayjay]

i had a similar prob a while ago in a block of flats
the main rcd was tripping at the same time every morning causing a whole wing of flats to lose their supply(this was the only rcd btw)
lots of sparkies had gone there but couldn,t find the fault
it turned out that an eldely tenant used to boil her electric kettle at the same time every morning , when it boiled the spout was pointing at the socket in her kitchen and the steam was going directly into the plug thus causing the rcd to trip
my how we laughed

 

[DNS1]

IR test 2 would be fine to test an RCD. Any leak between line and neutral wouldn't trip an RCD anyway so in this case you could diagnose with L and N connected to save disconnecting every load in the house.

 

[AP Electrical]

Ramp testing rcd then clamp meter on main earth with loads on- as an initial quick check, all you need is a few duff appliances and a laptop to trip the buggers out.

 

[DNS1]

Ramp testing rcd then clamp meter on main earth with loads on- as an initial quick check, all you need is a few duff appliances and a laptop to trip the buggers out.

Out of curiosity, can a laptop trip an RCD? It's got no earth...

 

[AP Electrical]

Sorry ment computer.. :s

 

[Edd]

Was just about to reply to the OP then relised that if after a week he aint found the fault then well we aint gona help him

 

[Dolman100]

Isolate the supply, join live and neutral together on load side, and IR test between joined L and N to earth.

Cheers.........Howard

PS GN3 explains it better, and it is illustrated.

This is a new one for me. Tried this today. Many thanks for sharing.

 

[NrVolts]

would an I.R. test pickup say damp in a socket? i would think it would find a waterlogged one but i was wondering if it would be effective if it was just a bit damp.