RCD Trips on Every Circuit

[luka B]

Hi Everyone ,
Recently got a Call from an old customer .
She had a Washing machine Delivered and since then She has No Power or Lights !

I went there and RCD had tripped and cut off all circuits .
Turned of all MCB's and put them up one by one .. Every single one Bar a 16 Radial Trips
the RCD when put in On Position .. Even the 3 X 5 amp light circuits trip the RCD ..

Ive never had this before .. usually its one circuit ..find and cure fault and Bingo .
It cant be that every circuit has a fault ..of course first thing i did was unplug the
new was machine and check the socket .. all OK ..

CAn anyone offer any advice on this Please

 

[Marvo]

An RCD won't trip if there's no load on it even if there's an insulation fault. Don't get sidetracked by the fact that switching any of the circuits on is causing it to trip, the fault will most likely be a low IR on one of the circuits.

What were your IR readings for a global test and each circuit.

 

[davesparks]

The new machine is faulty

 

[Deleted member 9648]

So you didnt do any tests and just cluttered off into the sunset leaving the client with no power while you wait for a response on a forum.??....:uhoh2:

 

[luka B]

Rigged up temp rcd Supply and am going back tomorrow .

Still cant under stand how it trips on Every single MCB Lights and Power .
Only one 16 Amp radial is ok .

 

[Marvo]

So you didnt do any tests.....

I'm kinda hoping that's not the case, if test results aren't forthcoming I'm going to close the thread because any advice given will only be guesswork.

 

[Deleted member 9648]

Rigged up temp rcd Supply and am going back tomorrow .

Still cant under stand how it trips on Every single MCB Lights and Power .
Only one 16 Amp radial is ok .

It could be a faulty RCD,I've had one or two over the years which trip as soon as any load is applied. However it is essential to carry out proper testing of the circuits,from what I have seen on this forum far too many assume a faulty RCD first....I find that is the LEAST likely cause.

 

[Marvo]

.......Still cant under stand how it trips on Every single MCB Lights and Power .
Only one 16 Amp radial is ok .

Probably because there's load on all the other circuits but zero load on the 16A radial.

Zero load = zero current flow which also means zero leakage current flowing which means RCD doesn't trip.

 

[Dave OCD]

If it's TNCS earth then could well be a neutral/earth fault, neutrals need separating to establish which circuit is the culprit.

 

[davesparks]

Rigged up temp rcd Supply and am going back tomorrow .

Still cant under stand how it trips on Every single MCB Lights and Power .
Only one 16 Amp radial is ok .

Easy, an N-E fault diverts part of the normal neutral current from all circuits, disconnecting the circuit neutrals and testing teh circuits will find the faulty circuit.

But if the installation was working before the new washing machine was fitted, then the RCD tripped when the washing machine was connected then I think it would be acceptable to take a wild guess at there being a fault in the washing machine and disconnecting that to check before starting testing.

 

[davesparks]

If it's TNCS earth then could well be a neutral/earth fault, neutrals need separating to establish which circuit is the culprit.

Why specifically TNCS? a N-E fault will exhibit the same symptoms on any earthing system

 

[UKMeterman]

Not quite so, read sections 9.5, 9.6 TNCS has a very little voltage difference N-E this can do strange things
http://www.beama.org.uk/download.cfm/docid/3FA319A6-4159-4816-87188608E386D98D

 

[davesparks]

Not quite so, read sections 9.5, 9.6 TNCS has a very little voltage difference N-E this can do strange things
http://www.beama.org.uk/download.cfm/docid/3FA319A6-4159-4816-87188608E386D98D

I can't access that on my phone, but I assume it is only considering a N-E fault of minimal impedance? The symptoms could just as easily occur on different earthing systems with different fault impedances and load currents. All N-E faults will result in diverted neutral currents and so cause what the inexperienced will see as 'random' tripping under the right conditions.

 

[Dave OCD]

Yeah fair enough but TNCS or PME in English can play strange tricks, as per the link above.