Thanks, I appreciate the quick reply. The total load is 400W plus the 450W existing lights etc. So I'm assuming as long as the total load is less than 5A I should be OK.
I’m looking at fitting a PIV unit but there’s no 13A supply in the loft only lighting circuits. The PIV has a heat element of 400W and I’ve calculated the rest of the lighting and bathroom extractor is about 450W (mostly LED lights). Is it ok to wire my fused spur for the PIV into the lighting...