On Jun 3, 11:06 pm, Owain wrote:

(a) Why do you need to RCD the cable?

Seemed like it couldn't hurt, belt and braces and all that.

(b) Why a 16A MCB in the shed, the spur should be limited to 13A by the
fuse in the FCU anyway. Or were you going to use an unfused spur, in
which case you can't use a 16A+6A MCBs anyway

'Cos 16A is what comes in the stantard Garage CUs. Now that you
mention it, it does seem a bit redundant...

(c) you could use a 30mA RCD FCU, no CU in the shed, a 3A FCU in the
shed off the socket circuit for the lights, and if lights failing with
power tools spinning down is the issue, a batter back up emergency light.

I planned on an RCD in the shed because I was a bit concerned about
the extra impedance of the 50m run if the only RCD was in the house.
If the impedance is not a worry then your solution is not only
simpler, but much cheaper as well. I had planned on using a (no-
maintained) emergency light as well.

(d) better to run a new circuit from the CU if at all possible.

Indeed, and I will, when I get around to fitting a decent CU. Thanks.
--
Rob