On 15/12/2020 11:08:09, wrote:
On 14/12/2020 15:22, wrote:
On 13/12/2020 15:17, Robin wrote:
On 13/12/2020 12:37, wrote:
One for our resident certified electrical installers ...
I want to add a spur to feed a wall-mounted smart heating
controller, which has a PSU as part of its wall-mount kit. I don't
want to have a fused spur plate on the wall so am planning on
putting an in-line fuseholder in the back-box for the wall-mount
kit. I don't have any concerns about whether this is safe, but I
can't decide whether it meets the regs or needs any specific labelling.
Can anyone here provide the answer?



I'm not certifiable (yet) but have a couple of questions and comments.
Perhaps I'm heading in the "certifiable" direction ;-)

First, what if anything do the manufacturer's instructions require?
There's nothing about protection

Second, I am not clear what - if any - means of local switching and
isolation you end up with.Â* An unswitched FCU to BS 1363-4 counts
(Table Â*Â* 537.4 in the regs): you can remove the fuse without risk to
life and limb.Â* But what you propose ain't to BS 1363-4 and AFAICS
could only remove the fuse by opening up the back box.Â* So I think
that's a problem.

You may be right but the fuse would only need replacing if the PSU
fails, and that is in the back box. All connections would be insulated
and I found an inline fuseholder with appropriate protections
(although I can't find it now) so I think it meets the intent, but
maybe not the letter, of the requirements.
Following that thought chain, the fuse could be non-replaceable and
considered part of the PSU. So something like
https://www.ebay.co.uk/itm//323268286316 in two layers of heat-shrink.

You ought to be able to isolate the PSU, ideally with a DPST swtich so I
don't see why you are so against a switched FCU.

It doesn't have to be co-located with the PSU as long as it's still
accessible.