RCD Trouble

eggy81

A friend of mine has been having a bit of bother with his rcd tripping at random times in the last 3 of 4 weeks. It has tripped 3 times in total in this period.

I told him I'd have a look and went down this evening. Luckily I had acess to a megger and I performed the insulation resistance test at 250v which came back at > 999M which would indicate no fault in the circuit.

This megger had the ramp test function so I connected it up and performed that test which gave me a reading of 17.5 mA.

Am I right in concluding that this would indicate a faulty rcd.

Thanks for the help.

2011

eggy81 wrote: »

I told him I'd have a look and went down this evening. Luckily I had acess to a megger and I performed the insulation resistance test at 250v which came back at > 999M which would indicate no fault in the circuit.

Intermittent problems are always the hardest to solve.

Normally I would test this at 500V.

Did you measure > 999 MΩ between earth and neutral?
Most likely the RCD is tripping due to a device that is plugged in to a socket circuit.
I have split the circuits that were protected by one RCD across a 2nd or 3rd RCD (or RCBO) to narrow this down in the past.

This megger had the ramp test function so I connected it up and performed that test which gave me a reading of 17.5 mA.

I would not think that the RCD is faulty. It may well have tripped at 17.5 mA at the top of a cycle.

mikehammer67

they can trip at 0.5 or above rated trip current

eggy81

Thanks for the replies lads. Been so long since I did any testing that I'd forgotten the rules on rcd tripping current.

I think I will probably put the kitchen on its own rcbo and see what happens next. The major problem is the freezer which has had to be emptied twice now.

They have one of those modulating pumps for keeping the water pressure up. I'm wondering could this be causing the issue.

It seems to come on itself at random times even if no one has used a tap or nothing is using water. Would this be normal or would it suggest loss of pressure somewhere. There are no visible leaks around the house anyway.

2011

eggy81 wrote: »

I think I will probably put the kitchen on its own rcbo and see what happens next.

Remember you should have at least 2 socket circuits for a kitchen.

The major problem is the freezer which has had to be emptied twice now.

Can you put it on a dedicated circuit?

They have one of those modulating pumps for keeping the water pressure up. I'm wondering could this be causing the issue.

In my experience most RCD problems are water related.

eggy81

2011 wrote: »

Remember you should have at least 2 socket circuits for a kitchen.



Can you put it on a dedicated circuit?



In my experience most RCD problems are water related.

The kitchen is on a ring circuit. Would I be better served splitting it into two radials putting the side with the freezer on its own rcbo.

Thanks again for your help.

mikehammer67

you prob can

best to split loads evenly if possible

ring circuits are no longer fitted in kitchens

deep freezers can also be wired mcb/13amp switched spur

2011

mikehammer67 wrote: »

you prob can

best to split loads evenly if possible

ring circuits are no longer fitted in kitchens

deep freezers can also be wired mcb/13amp switched spur

+1

Dufftronic

from my very limited experience of domestic wiring, white goods (specifically Fridge Freezers) are generally the cause of nuisance tripping. Leaky compressors on startup.