Andy Hall wrote:
For my cloakroom project, I am pondering on a few electrical and other
questions:

At present there is a central ceiling rose which has a lighting circuit
looping through it. In the conventional way, a pull cord switch is
connected to this and there is a separate feed of permanent and switched
phase, neutral and earth going to the ventilation fan.

To provide a little detail, the room is rectangular with the door at
one end of the long side. The ceiling joists run parallel to the long
dimension. The ventilation fan is towards one end of the room and
central and has a duct to deliver the exhaust air a few metres to the
edge of the house.

Make it far bigger than you think you need, then, and use a more
powerful fan, and if its hidden in the roof space, a really good quality
QUIET one that won't need replacing in 6 months...


There is not easy access from above, so work will have to be done from
below. I would prefer to minimise repair work on the ceiling plasterboard.

At one end of the room, further from the door, the throne will be
installed with concealed cistern covered with small granite shelf.
Above this, with a space for whatever, will be a wall cupboard which
will go to a height of about 200mm below the ceiling.

The intention is to do away with the ceiling rose and pull switch and
re-route the wiring to run on the walls. There will be a plate switch
inside the door,

Not legal unless the bathroom is very big. Outside with an isolator up
near the ceiling is conventional.

from which cable will run horizontally to the corner.
From there it will run vertically in the 150mm allowed space, behind
the cupboard, to the space above it.

Ideally, I would like to run a new cable from the existing ceiling rose
position, across the ceiling, above the plasterboard, drop it down above
the cupboard and make connections there.

This raises two questions:

1) In effect, this creates a spur - i.e. the daisy chain of the lighting
circuit comes to the ceiling rose position and the cable to feed the
lighting circuit to the edge of the room above the cupboard would be
teed from it. I suppose that I could run two cables and effectively
maintain the daisy chain. I can't find any rules on this in BS7671 one
way or the other.

All lighting is spur wired.


2) I need a solution for jointing the cables at the ceiling rose
position. Crimps are the obvious choice since the hole will be
repaired and covered. However, I could do with a solution to provide
the second required level of insulation etc. Conventional junction
boxes don't seem very suitable because of the screw terminals, although
I suppose those could be removed; but also I don't really want to make
the ceiling hole larger if I can help it. Is heat shrink tube
permissible in this application to provide the second layer of
insulation? Any other ideas?


Solder and heatshrink is allowed as is crimping. Those can be
permanently boxed in and meet regs. Unless you are an avid soldere ger
some crimps and a tool.

Ventilation:

3) I want to move the fan from its current ceiling mount position to
being fitted above the cupboard. There would then be a removable
grille above the cupboard. The idea is to make the ceiling clear, and I
should be able to reduce the noise of the already quiet Vent Axia fan
even further. I can't find any Building Regulations objection to so
doing. Anybody know different?

No, its fine. regs merely say you need a given airflow. How you achieve
it is up to you BUT fans in long tubes are very ineffective. IIRC
centrifugal fans are better than acxial.


4) I believe the Buiding Regulations specify that the fan comes on when
the light is switched on and should run for a period of time after it
has been switched off. However, I am intending to have two sets of
lights; one being under-cupboard and the other some downlighters on the
long wall or wall lights. So the question arises of whether the fan
should come on when the "main" light is switched on or when either is
switched on. Obviously I could do the latter with relays.

Best of all, use a humidity controlled fan with a manual override.


Comments?