29 Dec 2013
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United Kingdom

I have an outside cupboard, well its actually built into the house. I have a socket in it to power my 12 volt garden lights. The power for the socket is taken from a spur off a socket in the bedroom, which is on a 30 amp socket circuit for all the sockets in the flat. My question is would i be better to fit a consumer unit (2 mcb's and main switch) in place of the socket then obviously wire the socket and another socket into the consumer unit. I was thinking of doing it that way because i thought if i have problems with the lights then it will trip at the consumer unit in the cupboard rather than at the main board inside, but would it cause problems adding another consumer unit to the 30 amp circuit?

Any help would be grateful.


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No, because:

1. you can't fit a consumer unit or anything greater than 13A on a ring circuit

2. there won't be discrimination between the two circuit breakers so either or both will operate in the event of a fault on the outside light.

Provided the transformer for your garden lights is inside and in the dry then it would be fairly unlikely to give rise to a fault on the mains side.
Easiest solution would be to fit a fused connection unit (FCU) before the socket used for outside lights. This can will be down fused to offer discrimination between the spur circuit and the main house circuit and if the FCU is fitted within the property then you can isolate the socket without leaving the house. But saying that the fuse in the plugs of lights should deal with discrimination. Does your existing consumer unit have RCD protection?

Thanks for the replies

I didn't think i could use another consumer unit on a 13 amp circuit

There is a fixed fcu before the cable leads into the socket in the cupboard and it is fitted with a 13 amp fuse. The consumer unit does have rcd protection. The transformers for the lights are inside the cupboard screwed to the wall beside the socket so there is no chance water can get to them at all.

Would it be ok to take another spur from the existing socket in the cupboard so i can add another socket to give me a spare socket for the use of a lawnmower etc without having to unplug the garden lights which are on plug in timers which i would need to reset if i unplug the timer to use the socket for a lawnmower etc The lights use transformers of 170w in total although the total bulb wattage is only 120w although i may add to this in the future.


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Which would be more than safe even if i was using a lawnmower and a strimmer at the same time with the garden lights on.

That's all i would be using the sockets for and i'm not going to have the lights on during the day while i'm cutting the grass anyway!

Thanks PrenticeBoyofDerry for your help mate

At this point it would now be wise, to check that the RCD is 30mA and does protect this circuit you are adding to for outside use.
If not the FCU can be changed to one that has integrated RCD protection or a RCBO could be fitted to replace the MCB at the board, depending on the compatibility to your existing board.
The RCD is definitely 30ma and the FCU is on that circuit so it should be okay or do you think i should change the FCU to have an integrated RCD
If i did change the FCU to an integrated RCD FCU would that give better protection incase i went through the lawnmower cable (for example) than the standard FCU and 30ma RCD at the board or would it be a bit overkill?

a know the one in the consumer unit works well as i went through a cable in the kitchen when i went through a cable when installing an extra socket, and it tripped straight away with no shocks or bangs lol, the dodgy kitchen fitters had a cable where there really shouldn't have been one, no wonder they went out of business! The electrical installation was a joke. Saying that i should have put the power off before chasing the wall for the cable, lesson learned mate.
If you already have 30mA RCD protection on the circuit that these plugs are on then there is no requirement to add a second RCD unit.
It would give no extra protection unless as stated by EFLI, the one at the CU fails.

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