On Tue, 18 Aug 2009 17:49:31 +0100, "Dave Plowman (News)"
wrote:

In article ,
BodgeIt wrote:
I need to install an additional 2 way 13A socket in an upstairs
bedroom, the room has recently been redecorated and carpeted so I
don't really want to break into the ring main. The bedroom backs onto
the airing cupboard which contains an immersion heater fed from a 30A
mcb in the consumer unit. We've never used the immersion heater and
don't plan to in the future. So my intention is to disconnect the
immersion heater and wire the cable to a 13A fused spur inside the
airing cupboard. Then from the fused spur, through the wall into the
bedroom into the back of RCD twin socket. Any problem with doing
this? I'm assuming it's OK as long as the immersion heater is
permanently disconnected. TIA

First, are you sure it's a 30 amp MCB? Immersions are usually 3 kW, so 16
amp would be usual. You need to identify the cable feeding it as 30 amps
is too large for the normal 2.5mm TW&E.

However, you don't need to use an FCU when converting an immersion heater
circuit to a radial. Change the MCB to a 20 amp one. You can then have as
many sockets on that radial as you wish, as the MCB will prevent overload
of the cable.

You're correct, it is a 15A MCB, I confused it with the cooker MCB. I
thought fitting an FCU would be better so that if the central heating
ever fails and we need emergency hot water I can isolate the
additional socket and temporarily reconnect the immersion heater.