Wiring bathroom fan with run-on timer
Phil Hughes
run-on timer please?
The diagram with the instructions show the following (hope the ASCII
diagram comes out ok)
L--------[FCU]----[Light sw]-----------L1 Fan terminals
|----------------------L
N--------[FCU]------------------------N
(FCU is fused connection unit)
The instructions say the connections to the fan must be flexible cable.
I understand that because of the run-on timer, the fan needs a permanent
live, but I don't understand how to go about doing this - what cable etc
to use. I want the fan to be switched by the bathroom light.
Before realising that the fan needed a permanent live, my plan was to
run twin-core and earth from the ceiling rose (SW and N terminals) to
the FCU, then twin core flex to the fan terminals (which without the
permanent live is the opposite way around to the above diagram). But
then I can't see how to get the permanent live to the fan.
Help! Could someone explain what cables I need to take from where and to
what (eg any junction boxes required). Thanks.
--
Phil Hughes
Andrew Gabriel
Phil Hughes <ph...@phuse.clara.co.uk> writes:
>Could someone explain how to go about wiring a bathroom fan with a
>run-on timer please?
>I understand that because of the run-on timer, the fan needs a permanent
>live, but I don't understand how to go about doing this - what cable etc
>to use. I want the fan to be switched by the bathroom light.
>
>Before realising that the fan needed a permanent live, my plan was to
>run twin-core and earth from the ceiling rose (SW and N terminals) to
>the FCU, then twin core flex to the fan terminals (which without the
>permanent live is the opposite way around to the above diagram). But
>then I can't see how to get the permanent live to the fan.
You run triple and earth from the ceiling rose (Red=permanent live,
Yellow=switched live, blue=neutral). You should also use a 3-pole
fan isolating switch in the cable run, so you can switch off for
maintanence (this should be well out of reach of bath and shower).
You don't normally need an extra fuse, providing your lighting
circuit is protected by a 5A fuse or 6A MCB, and it wouldn't be
easy to add one into such a circuit unless you also included the
bathroom light on it.
--
Andrew Gabriel
Consultant Software Engineer
Phil Hughes
<and...@cucumber.demon.co.uk> writes
switch.
What about the flex? Do you use twin core and earth with the earth as
one of the lives (suitably marked with red), or is there also special
flex for this sort of thing?
PS did the ASCII diagram make sense to anyone? Looks wrong to me, but as
you've gathered I'm no expert :)
--
Phil Hughes
Andrew Gabriel
Phil Hughes <ph...@phuse.clara.co.uk> writes:
>Thanks. Will have to have another trip to the "shed" to look for such a
>switch.
Looks like a normal 1 gang light switch, except it has a very wide
rocker, extending most of the width of the switch.
>What about the flex? Do you use twin core and earth with the earth as
>one of the lives (suitably marked with red), or is there also special
>flex for this sort of thing?
Unless it's designed for mounting through window glass, I can't see
why it claims to require a flex. The ones I have (which I didn't
install, but have repaired occasionally) have the standard house
wiring solid core cable running to them, with some spare folded into
a recess in the back of the fan housing.
You can get 4-core flex, and if the fan requires an earth connection,
you would need to use that (if you use flex at all). It's going to
start getting messy though, as you are going to need appropriate
device to terminate the 4-core flex, with strain relief (could use a
ceiling rose designed for loop-in wiring I suppose, but I doubt any
of the fan switches will be designed for flex outlet). Does the fan
have a strain relief built in for its end of the flex?
>PS did the ASCII diagram make sense to anyone? Looks wrong to me, but as
>you've gathered I'm no expert :)
I didn't need to look at it to understand the problem, but looking
back now, I think I understand what it's saying.
Chris French
>In article <97tl0h$d...@cucumber.demon.co.uk>, Andrew Gabriel
><and...@cucumber.demon.co.uk> writes
>>In article <aj8jtJAR...@phuse.clara.co.uk>,
>> Phil Hughes <ph...@phuse.clara.co.uk> writes:
>>>Could someone explain how to go about wiring a bathroom fan with a
>>>run-on timer please?
>>
>>>I understand that because of the run-on timer, the fan needs a permanent
>>>live, but I don't understand how to go about doing this - what cable etc
>>>to use. I want the fan to be switched by the bathroom light.
>>>
>>
>>Yellow=switched live, blue=neutral). You should also use a 3-pole
>>fan isolating switch in the cable run, so you can switch off for
>>maintanence (this should be well out of reach of bath and shower).
>>You don't normally need an extra fuse, providing your lighting
>>circuit is protected by a 5A fuse or 6A MCB, and it wouldn't be
>>easy to add one into such a circuit unless you also included the
>>bathroom light on it.
>>
>Thanks. Will have to have another trip to the "shed" to look for such a
>switch.
>
wholesalers.
>What about the flex? Do you use twin core and earth with the earth as
>one of the lives (suitably marked with red),
Err, no! it lacks the necessary insulation.
>or is there also special flex for this sort of thing?
>
Yep, as Andrew said, you want 3 core and Earth, - has three insulated
cores, Red, Yellow and Blue, plus and earth. you should tag with red any
of the blue/yellow cores used as a live.
Normally used domestically for wiring two way switching, in 1mm ^2 or
1.5 mm^2 (this stuff is a silly price in Homebase BTW). Not sure about
the flex bit though, I know what the instructions say, but normally
you'd use a cable for fixed wiring, and as the fan is fixed I see no
need for flexible cable. I certainly didn't use it.
>PS did the ASCII diagram make sense to anyone? Looks wrong to me, but
>as you've gathered I'm no expert :)
>
No it was fine. There are different ways of arranging it physically
though.
--
Chris French, Leeds
Phil Hughes
<and...@cucumber.demon.co.uk> writes
>In article <s8HdWZDf...@phuse.clara.co.uk>,
> Phil Hughes <ph...@phuse.clara.co.uk> writes:
>>What about the flex? Do you use twin core and earth with the earth as
>>one of the lives (suitably marked with red), or is there also special
>>flex for this sort of thing?
>
>Unless it's designed for mounting through window glass, I can't see
>why it claims to require a flex. The ones I have (which I didn't
>install, but have repaired occasionally) have the standard house
>wiring solid core cable running to them, with some spare folded into
>a recess in the back of the fan housing.
>
>You can get 4-core flex, and if the fan requires an earth connection,
>you would need to use that (if you use flex at all). It's going to
>start getting messy though, as you are going to need appropriate
>device to terminate the 4-core flex, with strain relief (could use a
>ceiling rose designed for loop-in wiring I suppose, but I doubt any
>of the fan switches will be designed for flex outlet). Does the fan
>have a strain relief built in for its end of the flex?
>
I can't really see why it needs flex either, but the instructions are
quite cleat that only flex should be used. There is strain relief in the
fan case. Might be something to do with the design of the fan. The fan
body sits in a case which is recessed either into the wall or into the
ceiling space. But as the electrical connections are fixed to the case
rather than the fan itself, still can't see why this requires flex.
--
Phil Hughes
Phil Hughes
<newsp...@chrisfrench.org> writes
>>one of the lives (suitably marked with red),
>
>Err, no! it lacks the necessary insulation.
>
I just meant the flex part of the cabling, which would have insulation.
>>or is there also special flex for this sort of thing?
>>
>Yep, as Andrew said, you want 3 core and Earth, - has three insulated
>cores, Red, Yellow and Blue, plus and earth. you should tag with red
>any of the blue/yellow cores used as a live.
>
>Normally used domestically for wiring two way switching, in 1mm ^2 or
>1.5 mm^2 (this stuff is a silly price in Homebase BTW). Not sure about
>the flex bit though, I know what the instructions say, but normally
>you'd use a cable for fixed wiring, and as the fan is fixed I see no
>need for flexible cable. I certainly didn't use it.
>
I can't see a reason either, but the instructions are most insistent.
Will have to see what the switch is like, and then choose.
The fan is a Greenwood (=Marley?) is anyone is wondering.
--
Phil Hughes
Ed Sirett
Andrew Gabriel wrote in message <97uauc$d...@cucumber.demon.co.uk>...
>You can get 4-core flex, and if the fan requires an earth connection,
>you would need to use that (if you use flex at all). It's going to
>start getting messy though, as you are going to need appropriate
>device to terminate the 4-core flex, with strain relief (could use a
>ceiling rose designed for loop-in wiring I suppose, but I doubt any
>of the fan switches will be designed for flex outlet). Does the fan
>have a strain relief built in for its end of the flex?
>
a strain relief just before the connectors. If a fan is windown mounted
(even in a fixed pane) I think it is better to wire them with flex, I
usually use the isolator as the termination for the flex. I put the flex
through a knockout in the surface mounted back box and them put a figure
of 8 knot in the flex to act as a strain releif.
Ed Sirett
Property Maintainer - North London.
Chris French
>In article <gZeYxaEH...@spennithorne.demon.co.uk>, Chris French
><newsp...@chrisfrench.org> writes
>>In message <s8HdWZDf...@phuse.clara.co.uk>, Phil Hughes
>><ph...@phuse.clara.co.uk> writes
>>>What about the flex? Do you use twin core and earth with the earth as
>>>one of the lives (suitably marked with red),
>>
>>Err, no! it lacks the necessary insulation.
>>
>
>I just meant the flex part of the cabling, which would have insulation.
>
question......:-)
--
Chris French, Leeds
Phil Hughes
Sirett <e...@makewrite.demon.co.uk> writes
instructions say to use only flex. Good idea about strain relief if I
decide to use flex.
--
Phil Hughes
KJR
> The fan will be mounted in the ceiling, cable will not be seen. However,
> instructions say to use only flex. Good idea about strain relief if I
> decide to use flex.
If you're desperate to use flex, run the 4 core flex to a 4 terminal
lighting JB and a bit of triple+earth to the isolator. Strain
relief on the flex with a couple of cable clips mailed to a
joist/rafter
--
Ken Redman
please reply to: ken_r...@hotmail.com
Phil Hughes
>Phil Hughes wrote:
>> The fan will be mounted in the ceiling, cable will not be seen. However,
>> instructions say to use only flex. Good idea about strain relief if I
>> decide to use flex.
>
>If you're desperate to use flex,
Not really :) its just what the instructions say to use, don't know why.
Not made my mind up yet what to do. Probably off to a local trade place
tomorrow to see what they've got.
>run the 4 core flex to a 4 terminal
>lighting JB and a bit of triple+earth to the isolator. Strain
>relief on the flex with a couple of cable clips mailed to a
>joist/rafter
Good idea, thanks.
--
Phil Hughes
Phil Hughes
<and...@cucumber.demon.co.uk> writes
>You run triple and earth from the ceiling rose (Red=permanent live,
>Yellow=switched live, blue=neutral). You should also use a 3-pole
>fan isolating switch in the cable run, so you can switch off for
>maintanence (this should be well out of reach of bath and shower).
Would it be deemed acceptable to have the switch in the loft? The fan
will be recessed in the loft and all wiring will be in there. However,
access to the fan for maintenance will be by taking the cover off in the
bathroom.
--
Phil Hughes
Andrew Gabriel
If you want a strict answer, then if the switch isn't positioned
such that it's under the sole/direct control of a person whilst
carrying out maintenance, then it must be able to be locked in the
off position. Some, maybe all, fan isolators are lockable using a
small hole in each end of the rocker - a separately available
padlocked clip can be locked into these holes and prevent the
rocker being switched on.
Ed Sirett
Phil Hughes wrote in message ...
If you are putting the fan in the ceiling then unless the fan is
reachable from the bath or shower I'd simply put the 3 pole maintenance
isolator also in the ceiling nearby. Use a flush mounting plasterboard
back box for the switch.
Phil Hughes
<and...@cucumber.demon.co.uk> writes
isn't lockable, so will have to go nearby.
Thanks to all for your help.
--
Phil Hughes