I'm going to reuse a circuitbreaker position that used to power the bell
transformer, to provide a dedicated fused connection unit for a new alarm
system. The circuitbreaker is 6A, and I'd use a 3A fuse in the FCU, so in
theory I can use 1mm lighting cable.

But something is nagging me that I ought to use cable at least enough for a
13A socket, in case some future house owner swops the fuses for 13A? Is
that a best practice or am I being paranoid - what do the experts think?
Thanks

"keith" wrote
| I'm going to reuse a circuitbreaker position that used to
| power the bell transformer, to provide a dedicated fused
| connection unit for a new alarm system. The circuit
| breaker is 6A, and I'd use a 3A fuse in the FCU, so in
| theory I can use 1mm lighting cable.
| But something is nagging me that I ought to use cable
| at least enough for a 13A socket, in case some future
| house owner swops the fuses for 13A?

Even if someone swaps the fuse in the FCU for 13A, the circuit is still
protected by a 6A MCB. If someone upgrades the MCB then they should take
responsibility for ensuring the circuit is suitable.

That said, if you use 2.5mm you are probably okay for up to a 20A radial
circuit.

Owain

keith wrote:

I'm going to reuse a circuitbreaker position that used to power the bell
transformer, to provide a dedicated fused connection unit for a new alarm
system. The circuitbreaker is 6A, and I'd use a 3A fuse in the FCU, so in
theory I can use 1mm lighting cable.

But something is nagging me that I ought to use cable at least enough for a
13A socket, in case some future house owner swops the fuses for 13A? Is
that a best practice or am I being paranoid - what do the experts think?

You are being paranoid - 1mm^2 will be fine. If anyone changes the
purpose of the circuit again in the future it's their responsibility to
ensure that it's appropriately rated for the new use.

--
Andy

But something is nagging me that I ought to use cable at least enough for
a 13A socket, in case some future house owner swops the fuses for 13A?

That wouldn't matter, as it is protected at 6A. Indeed, you could swap the
6A MCB with a 3A MCB and not bother with the FCU.

Christian.