rcd tripping but very strange

[Dean barrow]

rcd tripped today wouldnt just reset so dropped all mcbs then one at a time put them back on , problem is so far 3 different mcbs have tripped the rcd each time i reset ,can get all on except one of these 3 each time i reset them all , it is raining here today if thats anything to do with it ! the 3 mcbs concerend are the lounge, part of the kitchen and outside power to pond cant get these 3 on all at the same time any ideas whats going on?

 

[DefyG]

Possibly a N-E fault, needs IR test.

 

[Dean barrow]

Possibly a N-E fault, needs IR test.

thanks would that just happen randomly , what causes it ?

 

[MJPD29]

Could be a damaged cable, could be water in connections like outside lights or pond as stated, could even be a faulty appliance. If nothing obvious it requires an electrician with testing equipment.

 

[Dean barrow]

Could be a damaged cable, could be water in connections like outside lights or pond as stated, could even be a faulty appliance. If nothing obvious it requires an electrician with testing equipment.

thanks probably need a sparks then

 

[MJPD29]

thanks probably need a sparks then

Check everything obvious first just in case you can see water build up in an outside light etc

 

[Dustydazzler]

As all of the above

unplug , safely disconnect everything

turn all circuits back on

if nothing trips methodically plug and reconnect loads and sooner or later the offending item will rear it’s head

 

[DPG]

The pond stuff has got to be the first thing to check here I reckon.

 

[Dean barrow]

think youre right about start with pond , but why is it 3 mcbs which are all different circuits but different one cause the rcd to trip each time , i know all the earths are in one block and neutrals are in another but surely if its a fault the circuit with the fault should be the only one that trips the rcd or am i missing something

 

[pc1966]

think youre right about start with pond , but why is it 3 mcbs which are all different circuits but different one cause the rcd to trip each time , i know all the earths are in one block and neutrals are in another but surely if its a fault the circuit with the fault should be the only one that trips the rcd or am i missing something

If you have a N-E fault then it trips when enough current goes astray. But as N and E are almost the same voltage (theoretically both "0V") what makes it trip is enough current flowing so the N-E difference is enough to cause an imbalance.

It can be frustrating and non-obvious this is happening, as traditionally it would be a L-N or L-E fault that caused something to go, but that is the nature of RCDs.

In the absence of professional test equipment (and knowledge of how to use it) then the above advice of disconnecting everything and testing as you add back is a good start. Anything about the circumstances that causes a trip are invaluable to whoever is tasked with finding the fault!

 

[timhoward]

rcd tripped today wouldnt just reset so dropped all mcbs then one at a time put them back on

Do you mean you tried each in turn, turning it off again afterwards, or left each one on and continued?

think youre right about start with pond , but why is it 3 mcbs which are all different circuits but different one cause the rcd to trip each time

Pure speculation on my part but supposing there was a Neutral - Earth fault on the pond circuit. If the pump was turned off, it wouldn't show up until enough neutral current was present to be diverted along this path. So it can sometimes be the case that one circuit has a wiring fault but it doesn't show up until another circuit is drawing some current. Hope that makes some sense.

 

[timhoward]

I agree with @DPG that the pond is a top contender. Is there anywhere along the circuit the stuff can be disconnected e.g. is there a 3 pin plug or a fused spur somewhere?

 

[Dean barrow]

think youre right about start with pond , but why is it 3 mcbs which are all different circuits but different one cause the rcd to trip each time , i know all the earths are in one block and neutrals are in another but surely if its a fault the circuit with the fault should be the only one that trips the rcd or am i missing something

 

[LastManOnline]

, it is raining here today if thats anything to do with it !

It's very likely it has a lot to do with it. And as the other posters have already pointed out the symptoms you describe with several mcb, s tripping the rcd strongly indicate a neutral earth type fault . Check all outside lights and anything else in your garden that is connected to your electrical system (outside shed). Ditto the pond pump.

 

[Dean barrow]

Yes there's a fused spur for the pond , I will disconnect that first ,just noticed the outside waterproof sockets seem to be on same circuit ,but the fused spur only controls the pond