On 06/08/2012 08:42, David WE Roberts wrote:
Checking where to run the wires whilst the studs are only covered on one
side.

DIYnot says

"Shaver sockets can be install a shaver socket either by connecting to a
ring main with a junction box (see Adding a spur to a ring circuit from
a junction box) or from an earthed lighting socket. The spur from the
ring main must be fitted with a 3amp fused connection unit before
connecting to the shaver socket (see Fitting a Fused Connection unit).
The fused connection unit should never be installed in the bathroom.

Connection from a lighting circuit can be made directly, but must be
earthed. "

Firstly, is this up to date?

First question really ought to be "is it right?", to which the answer is
"mostly".

If taking a spur from a ring circuit then the obvious way to do it would
be using a fused spur unit rather than a junction box in many cases.
There is also no prohibition on the spur itself being in the bathroom if
required and you place it in a position where it is unlikely to get
splashed.

Also you need give some consideration to supplementary equipotential
bonding - if your shaver socket is introducing the earth of a new
circuit in the bathroom, and the wiring is not already to the 17th
edition standard of having RCD protection on all circuits and main eq
binding to spec, then the earth of the new circuit will need including
into the EQ binding in the bathroom. (the actual connection can be
"close" rather than in the room if required)

If so, it seems I have two simple options for the upstairs bathroom

(1) Drop a cable down from the loft which comes off the upstairs
lighting circuit

Yup

(2) Spur off the upstairs ring main and put the fused connection unit in
the wall outside the bathroom.

Or inside if easier.

Going off the lighting seems cheaper and simpler.
What are the downsides?

None really, and in many cases it is actually simpler.


--
Cheers,

John.

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