Mark Carver wrote:


It's as old as the house, (20 years). The 16A breaker feeds an
(emergency only) immersion heater. Could I upgrade that breaker to 32A
(assuming suitable MCBs still exist for my model of CU ?) and run the
new ring main from there, making the immersion heater effectively a
spur ?

The proper answer is no: fixed water heaters should have their own
dedicated final circuit; this is a clear requirement of the Regs.

The pragmatic view is that IF you're accumulating tuits to fit a bigger
CU, AND you can be SURE the immersion won't be used other than in the
case of a boiler breakdown, AND you can be sure no-one else in the
household will violate that assumption, AND you'll restore to fully
compliant before you sell, you won't in fact be creating anything
actively dangerous.

At least, that appears to have been the reasoning of the professional
electrician who ran out of ways on the CU in this place after putting in
a new ring for the garage conversion - having I assume consulted with
the previous owners, the upstairs ring was chosen as the one to sneakily
add the only-in-emergency immersion to...

Going back to your actual requirement - one other perfectly reasonable
solution is to run your conservatory sockets as a *fused* spur from a
nearby point on the ring. 13A should be plenty for the conservatory's
requirement - a coupla lamps, boombox, fanheater in exceptional circs.
Stick the FCU - switched or unswitched - next to the socket you're
teeing off, consider using one which comes with an RCD if the downstairs
sockets aren't already RCD'd (wot with conservatories being
semi-outdoor), label the FCU neatly, campers of happpiness all round.

Stefek