RCD Tripping after heavy rain

[Don246]

Can anyone help please. My RCD is approx 13 years old, and recently during/after heavy rain has tripped out.
The RCD switches on OK after isolating the MCB's
I have outside lights which I thought maybe to blame, so I installed switches (single pole) to both, but with both off the RCD still trips
Could the cause be Neutral/Earth contact?, and if so would double pole switches cure the problem

 

[securespark]

Well, you are half-way there. You say that when you isolate the mcb's the RCD is resettable. That means the fault lies on one of those isolated circuits. Try switching each mcb back on in turn. Which one trips the RCD?

This will be the affected circuit.

Single pole switches only isolate the live, bur the rcd is looking for imbalances between L - N - E.

Your first job is to identify the faulty circuit, though.

Often if joints get damp the RCD can trip. Or water using appliances develop faults and they trip.

Is it damp/wet under your floorspace on the ground floor?

 

[Don246]

Thanks for the info

Unfortunately this has only happened when we are out, therefore no MCB causes the RCD to trip on our return
No there is no dampness under the floor
Tonight I have tried to reproduce the problem by using a watering can over the lights to no avail (though the neighbours must have been bemused!!)

 

[securespark]

Well, they may grow.... after all, they contain bulbs....

 

[plugwash]

especially if there is a lot of computer av or similar equipment it will be hard to reset a rcd with all cuircuits on because a lot of stuff has more earth leakage on startup than in normal use

 

[ban-all-sheds]

My RCD won't reset if there is any load on - I have to switch off all the MCBs first. I think it's a design feature.

 

[Don246]

Problem solved, a downpour the other night showed the way
Unknown to me an appliance plugged in to a RCD plug (in this case my pond pump) will not only trip itself when a fault occurs, but will also trip the consumer unit RCD as well
This somewhat defeats the object of me using an RCD plug for the pump to isolate it from the main circuit so that fault occurs- only the single RCD trips and your freezer etc is OK- you live and learn

 

[ban-all-sheds]

Unless you have a time delayed main RCD, there is never any guarantee of discrimination when you have two in the same circuit.

The only way round it is to use RCBOs instead of a multi-circuit RCD, at least then you only trip 1 circuit, not several.


And your F/F shouldn't be on an RCD anyway.

 

[plugwash]

Problem solved, a downpour the other night showed the way
Unknown to me an appliance plugged in to a RCD plug (in this case my pond pump) will not only trip itself when a fault occurs, but will also trip the consumer unit RCD as well
This somewhat defeats the object of me using an RCD plug for the pump to isolate it from the main circuit so that fault occurs- only the single RCD trips and your freezer etc is OK- you live and learn

if your board is a split load i would stick a rcbo in the non-rcd side and run everything outdoors from there

also the pond pump should be replaced if its causing tripping

 

[ban-all-sheds]

Err... just thought. Wouldn't a pond pump be underwater? How could rain make it any wetter?

 

[plugwash]

i've seen at least one pond with the pump under a paving slab near it and not actually in the pond

running a fountain and waterfall