I have to install an extractor fan into our upstairs bathroom and
have a couple of questions to anyone who might have done this:
Firstly, should I drill from the inside going out or the outside
going in? And secondly are there any unforeseen complications that the
novice DIY person like me might miss and should I call a professional?
Just done this for the first time in my kitchen...
I would start on the outside. Spend some time working out
whether both sides of the bit of wall you intend to drill through
are actually clear. A drainpipe across the front of your fan
will not help! Assuming you have cavity walls, I would make
the appropriate size whole in the outer skin from the outside,
then drill pilot holes through the inner skin so that you can see
where the fan will be. Then, I would drill out the rest from the
A handy hint: get a big cardboard box and duct tape it to the
wall below where you'll be drilling. Stone dust is a pig to get
out of tile grout etc. The box should catch most of it.
The minimum effort/maximum cost way is to hire a core drill and just bore
Minimum cost/maximum effort is to bore a number of holes then knock the wall
out with a hammer and chisel.
As to 'inside out' or 'outside in' you may have to drill from both sides
unless you have a very long drill.
Don't worry too much about damage around the hole, as you normally have a
plastic surround on both the inside and outside to cover damage around the
Complications - as stated in another reply, make very sure that there are no
obstructions inside or out where you plan to drill.
Also check that there are no services running down the inside of the wall.
Do you have cavity wall insulation?
I don't know if this is an issue - just had a vision of loose insulation
pouting out of the hole :-(
Be careful working outside - an SDS drill can wallop a big hole in the wall
but can also hurl you off the ladder with the recoil :-)
You should be fine DIYing it - just go cautiously.
On 12 Nov 2003 02:35:53 -0800, email@example.com (Caher) wrote:
Running power cabling within the cavity is not recommended. Some of
the reasons include if the cavity is filled with insulation at some
future point in time there could be a chemical reaction between the
insulation and cable. There is also a consideration with regard to
power rating and heat transfer. Hardly likely to be a major issue with
a fan which is almost always low power (I'm assuming this fan doesn't
have a heater built in), but could be later.
The fan should be a spur from the upstairs ring main, not the lighting
circuit. And upstairs ring mains tend to come up from the floor rather
than down from the loft. Note the word "tend", you can't count on it.
So you might want to think about coming down rather than going up.
Furthermore you should have the fan fed via a fused spur which has a
3A fuse. Don't connect it directly to the ring main because it's
likely that the fan would burn out before it took the fuse (or MCB)
down. It's a low power device.
On 12 Nov 2003 16:11:38 -0800, firstname.lastname@example.org
Actually....you may be okay with this. I was coming from the direction
that "appliances" should be fed from ring circuits (or spur...), and
lights from lighting circuits. But I haven't seen anything written on
tablets of stone to advise that it has to be that way.
Not that a fan is an "appliance", but if it is generating light then I
would assume it might have a problem ;)
Thats the way we wire them.
From the bathroom fitting we take a 3core and earth (6243Y) to a 3 pole fan
isolator (outside of the bathroom) then another 3core and earth to the fan
itself. The 3 core carries a permanent live, a switched live and a neutral.
Please remove #NOSPAM# if replying via email
I would have thought that your idea is bloomin' dangerous - by
connecting the "permanent live" to the sockets and the "switched
live" to the lights the fan is in effect connected across two separately
fused circuits and a fault at the fan may not cause enough current to
flow to blow both fuses. Also consider the case where the fan actually
connects "SL" to "PL" internally, perhaps in a fault condition (who
knows what the electronics do?). In this case you have created a huge
circuit, partly wired in (usually) 2.5mm cable, partly in (usually) 1mm
cable and protected by what amounts to probably a 38A MCB (32A+6A). Not
only that, but you have bridged the two neutrals too and this could
cause big problems if, as is often the case these days even upstairs,
your sockets are wired via an RCD but your lights are not.
The only instance where I would consider spuring a typical run-on fan
from a sockets circuit would be where the fan is controlled in some way
*other* than via the light switch. It may have its own pullcord, or a
door switch, or it may be controlled by a humidity sensor or even a PIR.
Martin Angove: http://www.tridwr.demon.co.uk /
Don't fight technology, live with it: http://www.livtech.co.uk /
I think these extractor fans are not a good solution anyway. Theyre
not particularly effective, theyre noisy and annoying, and the
bearings are guaranteed to deteriorate making them very noisy. And
they simply throw your heat away.
HRV, which costs very little more, works like a fan but recovers most
of the heat.
A window lock enabling it to be locked 1/4" open - good, effective and
free for most of the year, but not so good for the coldest few months.
Dehumidifier - a bit more to install, much more efficient, doesnt
ventilate or lose any heat.
Finally the simplest option of all, an adjustable vent. Easy, cheap,
simple, no run cost, and effective year round.
Anything but a fan, they are just the worst option.
"Martin Angove" wrote
| > In this case the fan has two live connectors. One to power the fan
| > and electronics and one connected to the switched live feeding the
| > lamp(s).
| I would have thought that your idea is bloomin' dangerous ...
| consider the case where the fan actually connects "SL" to "PL"
| internally, perhaps in a fault condition (who knows what the
| electronics do?). In this case you have created a huge circuit,
| partly wired in (usually) 2.5mm cable, partly in (usually) 1mm
| cable and protected by what amounts to probably a 38A MCB (32A+6A).
And if the lighting circuit in the bathroom and the socket circuit borrowed
from (because there shouldn't be a socket circuit in the bathroom ...)
happen to be on different phases ....
Another reason will become clear if you consider that the ring circuit might
be fed via an RCD and the lighting circuit not...
More fundamentally though it violates regulation 314-01-04 which says that
the wiring of final circuits must be kept electrically separate.
I can't find the beginning of this thread, but whomever it was that said:
Locking up..... :)
I was under the impression that fan circuits would be run as a spur
from the upstairs ring. I guess I'm basing that assumption on a
previous house I owned where I know that was the arrangement (and I
didn't wire that property, it must have been before the 16th ed came
Could you please explain what is wrong with running a fan circuit as a
spur from the upstairs ring? I would assume from a technical
standpoint that providing it is properly fused (that is, minimum fuse
rating - 3A?) and appropriate cabling is employed then it would meet
the requirements of the 16th edition regs. Having got my 16th edition
regs certificate earlier this year I'm wondering what I've missed!
Always willing to learn....
Here are two resons:
1) It mmight not be obvious to someone that supply is from the upstairs
ring rather than the downstairs lighting. Not withstanding that there
ought to be a service isolator for the fan.
2) If the fan is the sort that requires both permenent and switched live
supplies (such as timed overrun models) then you will have also to
supply switched live from two seperate circuits. Which not only is contrary
to the regs but poses hazards for maintainers and might even make two
circuts have common live connections through the fan timer circuits.
Ed Sirett - Property maintainer and registered gas fitter.
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