Very strange RCD tripping

[rich1608]

Hello

I'm wondering if someone can shed any light on a peculiar RCD tripping problem please. It's feeding four socket rings along with garage and the PV system is also connected through it. What happens is the RCD sometimes trips between 09.00 and 09.30 in the morning and only in winter. A clamp meter on the L and N on the supply side shows 21mA leakage which is cumulative from the four socket rings. The property has gas CH and hot water underfloor heating so no electric heating. Lighting circuits are not fed through the RCD.

Any suggestions are gratefully appreciated! Many thanks

 

[telectrix]

with a standing leakage of 21mA, it won't take much more for a trip or 3. have you ramp tested the RCD both with and without circuits connected. had similar on a dual RCD CU. I shifted the RFC with the highest ( 13mA) leakage over to the other RCD and that cured the problem

 

[Deleted account]

Four rings garage and pv on one 30 mA RCD.


there is a natural earth leakage in any circuit. Th3 older the circuit the mor3 leakage occurs. Also the more appliances plugged in the more earth leakage.

it could be a combination of all the earth leakages or the. RCD has gotten a bit sensitive.

 

[rich1608]

Thanks for your replies. I don't have a ramp tester but it's worth mentioning that the RCD is a MK 5780s dating from 1997 when the CU was installed. The RCD is the only one fitted, the other circuits (lights, smoke alarm etc..) are just on MCBs.

 

[telectrix]

may be time to upgrade CU to a RCBO type.

 

[pc1966]

A "30mA" RCD is specified to trip somewhere between 15-30mA so it is more of a surprise it has not tripped before!

Really the only sane solution is to consider a CU upgrade as @telectrix suggests. These days RCBO are not much more expensive than a dual-RCD board and far less trouble from cumulative leakage. And when you do have trouble it is easy to locate the circuit responsible and inconvenience minimised until fixed.

 

[JBW175]

As others have said, it’s time to upgrade to an RCBO board.

I’m sure that there’ll be a sparky on here that covers your area and will be happy to quote.