mira magna digital shower install

[jammo]

Hi
I am about to install a mira magna digital shower . The digital box and pump unit will be in the loft and the problem is that I need to have a 3amp fused spur switch to wire it into. The most convenient option would be to create a spur coming off the immersion heater (which is never used) switch in the airing cupboard. Would this be OK to do this or is it essential that it goes to a spur off the sockets ring main....Thanks in anticipation!

 

[securespark]

This is a bit of a grey area:

7671:2008 does not say you can't.

The OSG advises you cannot.

If you have a 16A (or 20A) MCB covering the immersion circuit AND the immersion is no greater than 13A, then you could safely extend from the mains side of the immersion switch to another FCU, then use this to feed the shower pump via a 3A fuse.

I would put the shower FCU in the airing cupboard and a DP switch in the loft.