A quickie - FCU to double socket: adding a light

[domesticbadger]

Hi all,

Just wanted to ask a quickie here, as I'm confusing myself about what a previous owner has done with some garage wiring.

Basically, attached garage has a double switched wall box in it (and has since prior to my ownership). Some investigation this weekend seems to suggest it runs off a FCU on the other side of the wall (in the living room). This was wired a bit cack handed, with the feed/load all mismatched, which I've corrected. It's a bit odd, as the PO was an old guy who had a office job, and the job looks very much like it's been a paid job by a competent professional.

Anyway, through some works I did more than a year ago, I used a 2 foot (approx) fluorescent strip light and added a fused plug, then used it from the double switch with it crudely attached to the roof baton as a 'make do'. The time has come to make something a bit more permanent.

I've got a light switch wall box (the 'workshop' variety) and I've got a basic ceiling rose knocking about. The idea is to spur off the socket to add a simple switched ceiling light.


So, I'd planned on spurring off the double socket in the garage (which is the only thing off the FCU in the lounge), then to the switch, then off to the ceiling rose. As the circuit should already be protected by the 13A FCU, is it excessive (or even necessary) to put a 3A FCU on the lighting spur?

The garage itself is a glorified shed, and I tend to only run basic things off the sockets (orbital buffer, mower, dremelt etc.) if that's of any consequence.

Advice appreciated, questions welcome!

 

[EFLImpudence]

As the circuit should already be protected by the 13A FCU, is it excessive (or even necessary) to put a 3A FCU on the lighting spur?

It is, as you have realised, not really necessary. Some will disagree.
It is one of those things that is just done as a matter of course, with no thought, and as a switch will be required an FCU is often used.

The garage itself is a glorified shed, and I tend to only run basic things off the sockets (orbital buffer, mower, dremelt etc.) if that's of any consequence.

No. That is not relevant to the light.

 

[domesticbadger]

It is, as you have realised, not really necessary. Some will disagree.
It is one of those things that is just done as a matter of course, with no thought, and as a switch will be required an FCU is often used.


No. That is not relevant to the light.

No problem, thanks. I will probably fit one just for the sake of that extra bit of safety I think.

As per the socket load, this was just in case a query arose that related to the total potential circuit load that the spur would be subject to (as both the lights and the socket run off the 13A FCU).

 

[sparkwright]

Assuming the garage socket is fed by the FCU in the lounge, normal practice would be to run a 2.5mm t+e cable from garage socket to a new switched FCU (typically served with a 3 or 5 amp fuse), with a 1.0 or 1.5mm t+e to the light.

May be worth checking the cable sizes to the existing garage socket are adequate, since you have already found there has been an issue with the FCU being incorrectly connected.

 

[EFLImpudence]

I think that was the point of the question.

The OP had worked out for himself that sometimes there is no reason for "normal practices".

 

[domesticbadger]

Thanks for the help all.

Finished this off today, bit of a delay with boarding out the ceiling and putting the feed through for the pendant.


The original socket (now wired correctly) was 2.5. I've moved the socket to a more sensible location (it was mounted high up on the block wall), spurred off a run of 2.5 to a switched FCU, protected by a 3A fuse, which sits half way up the wall in the corner. I've then routed the 1.5 from this, through some 20mm round conduit, up through the bottom of the switch, then 1.5 up through some more conduit to the ceiling, where it then feeds to the pendant (all 3 core T&E).

Looks well for the extra detail - it's quite obvious what the FCU switch will isolate, but I may still mark it up in case someone daft decides to play around with it when I'm not about.


Appreciate the help!