Why is an FCU max. 13A.

[Bobble23]

I was at a customer's yesterday who wanted three double sockets added to a room which currently only has one double socket which is spurred off the ring. I explained that we couldn't spur off the spur as the first spur can only take 27A, so suggested that the solution would be to replace the existing socket with an FCU and then give him as many sockets as he wants from that (he's only using the new sockets for a computer, etc., so 13A should be plenty for him).

His question to me was, if the original spur can take 27A, why does the FCU have to be as low as 13A? It's not a big deal in this case, as he's going to get what he wants, but he was just asking out of interest and I couldn't come up with much of an answer other than there's not really anything on the market bigger than 13A (other than, say, a single MCB which would start looking a bit silly).

Have I missed something here? If anyone can come up with a better answer it'd be much appreciated.

Thanks.

 

[GLENNSPARK]

whats the OPD top end?

 

[yellowvanman]

Whilst a double socket could take 2 x 13A plugs, its highly unlikely that it would need to and a 2.5mm T&E has a current carrying capacity of 27A (clipped direct).

By putting in a fused spur (13A fuse) there is no other way that can limit the current taken by a spur of more than 1 two gang socket

 

[GLENNSPARK]

Whilst a double socket could take 2 x 13A plugs, its highly unlikely that it would need to and a 2.5mm T&E has a current carrying capacity of 27A (clipped direct).

By putting in a fused spur (13A fuse) there is no other way that can limit the current taken by a spur of more than 1 two gang socket

27 1/2A......:tounge_smile:

 

[Octopus]

Try asking the fuse manufacturers if they will make a 20A cartridge fuse! and the accessories manufacturers the same question!

 

[telectrix]

you could put a 16A or 20A MCB ( depending on the capability of the RCF to supply that current from a single point) in one of those wylex 2 module housings.

 

[Guest55]

whats the OPD top end?

continuing with my esteemed forum collegues comment , discrimination for a start ,
as any fuse bigger than 13A isnt going to operate before the 30 / 32A device at the CU.

plus the fact that its recommended to have loads greater than 3kw on dedicated circuits for another.

 

[Hawkmoon]

Are you really going to want a spur to take upwards of 27A when the ring in total is 30A?? - The 13A limit is just fine!

 

[telectrix]

if it's only for IT gear, then 13A is well adequate.

 

[Pete999]

Are you misinterpreting a spur, it doesn't have to be a FCU does it? only saying

 

[Hawkmoon]

Are you misinterpreting a spur, it doesn't have to be a FCU does it? only saying

No, agreed, but a twin socket on a spur is pretty unlikely to pull more than 13A, wouldn't you say?

 

[SPARTYKUS]

Leave the spur bit of 2.5 dangling in free air, we're up to 30A now

 

[Hawkmoon]

Leave the spur bit of 2.5 dangling in free air, we're up to 30A now

Deep