Garage RCD Intermittant Tripping

[Olivias Grumpy]

Hi
Problem with garage supply
I have a small consumer unit in Garage. 1x 6a and 2 x 16a MCBs
And. 63a RCD

For no obvious reason the RCD trips
I’ve isolated all circuits from CU.
I.e. removed all neutrals and internal earths and turned MCBs off

Still trips for no apparent reason

Garage is fed via 6mm twin and Earth cable from 32a mcb in main house CU. Also has a separate 6mm earth.
The mcb in the house is not RCD fed.
The rest of the house is controlled by its own RCD.

The house RCD has only ever tripped if anything in the house is a problem.

Any thoughts please?

 

[Harry Bloomfield]

For no obvious reason the RCD trips
I’ve isolated all circuits from CU.
I.e. removed all neutrals and internal earths and turned MCBs off

Where is the RCD located, that is tripping? If it is located in the house, the feed from house to garage might be the cause.

I know you said you completely isolated everything in the garage, but all neutrals and lives need to be disconnected, to ensure none of the circuits are causing the trip, then added back one at a time, with a suitable test interval between.

 

[ericmark]

I find there is a point when it time to abandon trial and error. Look for the easy things of course, water ingress etc. But at some point you need to get the meter out and test, the VC60B shown will cost around £35, if not tripping all the time you can try monitoring the leakage but either way the meters cost around the £35 mark, and for a one off job is it worth it?

I’ve isolated all circuits from CU.
I.e. removed all neutrals and internal earths and turned MCBs off

That seems to point to the RCD, and a RCD tester is not cheap, I would think cheaper to replace RCD than to buy tester.

 

[Olivias Grumpy]

Hi
The RCD is in the consumer unit in garage.
I isolated the 3 circuits to check if it was 1 of the circuits causing the problem
But with no wires connected, apart from incoming feed and extra earth, it still trips.

 

[Harry Bloomfield]

Hi
The RCD is in the consumer unit in garage.
I isolated the 3 circuits to check if it was 1 of the circuits causing the problem
But with no wires connected, apart from incoming feed and extra earth, it still trips.

Then, unless there is damp leakage, the RCD must be faulty.

 

[Olivias Grumpy]

Hi ericmark
That’s I am now.
Would an RCD trip if there was a problem either incoming cable?

So I’ve elected to buy a new RCD.

Had a quick Google and found on the B&Q website a British General 43a device. It’s in their Clearance section priced at £2!!!
So I’m off to get one at nearest Warehouse Store

I’ll be back soon

 

[Olivias Grumpy]

Then, unless there is damp leakage, the RCD must be faulty.

See previous reply to ericmark

Thanks Harry

 

[flameport]

It’s in their Clearance section priced at £2!!!

That's because it's an obsolete Type AC which is not an acceptable option for the vast majority of circuits.

 

[EFLImpudence]

43A is not likely. Have you spelt 63 incorrectly?

Anyway, it is the 30mA that is the important number.

 

[Olivias Grumpy]

Hello Flameport
It’s got the same markings as the my Hagar that is currently in situ.
For £2 it’s got to be worth a try.
Just paid for it. On my way home to fit.

Incidentally why is it obsolete?
Must still be safe or BandQ wouldn’t/ couldn’t sell it ?

Actually it has same markings as the one in the house CU.

 

[Olivias Grumpy]

43A is not likely. Have you spelt 63 incorrectly?

Anyway, it is the 30mA that is the important number.

Typo sorry
Specsavers next on list

40A. 30ma

 

[Olivias Grumpy]

Ok
New device fitted
All circuits re-connected
Everything works so far

Time will tell.

 

[oceansoul]

Why have you replaced a Hager RCD with a BG RCD? Consumer units are type tested with same manufacture parts. (Unless of course BG is rebranded Hager).

 

[Olivias Grumpy]

Because it is readily available
It complies with same safety requirements.
It is physically compatible

Why would anyone fit Michelin tyres to a car , that left the factory on Nexen?

And there is no name on Consumer Unit housing. It contains 1 hagar RCD and 3 MCBs (2 Wylex and other). And it’s been like that for 29 years

 

[JohnW2]

It’s got the same markings as the my Hagar that is currently in situ. ... Incidentally why is it obsolete?

It is strictly true that the latest version of (Amendment to) the Wiring Regulations says that such a type of RCD should now rarely be used (only in certain specific situations, which would not apply in your case).

Having said that, goodness knows how many millions of them are currently in service, and probably will continue to be in service for a long time to come.

Kind Regards, John