Two cables connected to FCU

[crooky]

Hi All,

We're having a conservatory built and I'm moving the extractor fan. The fan is connected to an FCU which is turned is connected to a double socket. The double socket is part of the ring main.

I've disconnected the extractor fan and wanted to completely remove the FCU. However, there is also another cable connected to the FCU which is sharing the same connections as the cable from the double socket. Therefore, is this common practice? and can anybody suggest what this cable may be connected to? It just disappears up a stud wall.

Many thanks.

 

[Taylortwocities]

How many cables go into the double socket?

If it is two then it sounds like the FCU is forming part of the ring with the cable going up the wall to the next socket.

If its 3 cables (with one going to the FCU) then the other cable from the FCU is a spur from the FCU which is not allowed.

To be absolutely sure you'd need someone who knows how to use a test meter.

 

[crooky]

Hi Taylortwocities, many thanks for your reply.

The double socket has three cables. Two which form part of the ring main and a third which is feeding the FCU. I only expected the one cable to be supplying the FCU and was suprised to find the other cable. I've checked all the sockets upstairs and they all have just two cables. We do have a central heating boiler in the kitchen so it's a possibility the cable goes through the joist and over to the boiler.

As far as I'm aware this is how the wiring has been since the house was built. The house is about 14 years old but we've lived there for the last eleven years and the wiring hasn't been modified whilst we've been here.

I think its time to call an electrician!

 

[Taylortwocities]

Yes, it sounds like the FCU is a spur with something else spurred from it - that isnt allowed.

Find a qualified spark at www.competentperson.co.uk

 

[pbar]

Yes, it sounds like the FCU is a spur with something else spurred from it - that isnt allowed.

Find a qualified spark at www.competentperson.co.uk

But isn't it only not allowed if the extra appliances are connected to the feed and not the load.

 

[davy_owen_88]

Correct, a single or double socket can only feed one unfused spur, so the FCU is the first spur and anything connected to it on the input/supply side is another spur, hence 2 spurs from one double socket which isn't allowed.

If the 2nd spur is fed from the output/load side of the FCU then that is fine as you can have as many spurs after an FCU as you like because the supply cables are limited to 13A.

 

[pbar]

Correct, a single or double socket can only feed one unfused spur, so the FCU is the first spur and anything connected to it on the input/supply side is another spur, hence 2 spurs from one double socket which isn't allowed.

If the 2nd spur is fed from the output/load side of the FCU then that is fine as you can have as many spurs after an FCU as you like because the supply cables are limited to 13A.

Cheers, you've made that very clear.
I always thought you could have a spur, from a spur, from a spur and so on, connecting whatever you like, as long as everything is on the load side of the first FCU. As then everything is protected by that one fuse.

 

[Taylortwocities]

you can have as many spurs after an FCU as you like because the supply cables are limited to 13A.

You are pre-supposing that the fuse in the FCU is 13A.
Its probably only 3A as its only a fan on there.

The OP could leave the FCU in situ, and upgrade upgrade to fuse to 13A and move the Mythical spur to the load side.

He needs to find out what that cable powers BEFORE DOING THAT.

 

[333rocky333]

An FCU is not always wired as a spur from the ring, it may also be part of the ring.

The cable in the stud wall to the FCU may be one leg of the ring , then links to the socket where the other leg of the ring is.

There may be a third wire in the socket spurring off to somewhere else.

 

[Taylortwocities]

Thats why I said

To be absolutely sure you'd need someone who knows how to use a test meter.

 

[333rocky333]

sorry TTC
Misread it.

 

[Taylortwocities]

No probs, I cant be @rsed to all read of it sometimes