I have relocated an existing pull switch to outside its bathroom. Now
I want to change it to a 'normal' switch. However, it has more wires
than terminals in a normal switch. I think I need a special type of
switch (boiler?), with more terminals. Can anyone advise me whch type
of switch I need and how it should be wired?
The existing pull switch has four terminals and an earth terminal. It
- Earth (which I assume I wire to the new switches metal box)
- Red to one terminal
- Black to one terminal
- Second red shared to two terminals by way of a link
The switch activates a ceiling light and also a shared extractor fan.
Any help would be much appreciated. Nick
The two reds should be in one terminal point on the switch, the COM
terminal. The black should actually be covered with a red coloured sleeving
to mark it as a switched live to the light fitting on the ceiling. The
setup you have is one red is from the mains and is the live feed to both the
switch and also the continuous feed for the fan. The black from the fan
will be connected to the black inside the ceiling rose of the light fitting
along with a switched red to make the timer in the fan come on when the
Thanks for this info, but I am still a little unsure of how to
proceed. Am I right that a normal light switch (with one COM and one
L1 terminal) will not be usable?
If I need another type of switch (a normal switch with four terminals
is what the other bathroom has) can you tell me what this is called,
and which wires go where?
Thanks very much again for your reply. Cheers Nick
| Thanks for this info, but I am still a little unsure of how to
| proceed. Am I right that a normal light switch (with one COM
| and one L1 terminal) will not be usable?
| If I need another type of switch (a normal switch with four
| terminals is what the other bathroom has) can you tell me
| what this is called, and which wires go where?
I don't think you've got a ceiling light switch - which would be single-pole
two-way (COM, L1 and L2 terminals)
I think you've got a DOUBLE-POLE ceiling switch of the type used for
electric showers, one pole is doing the light, and the other pole is doing
the *shared* fan. Is it a square plate and decidedly chunky in style? -
they're usually rated at 30 or 45A for showers rather than 6A for
IE wired something like this (SWa = switch a, which has two poles)
LIVE -------------- SWa Pole 1----------- LIGHT -- Neutral
|-- SWa Pole 2-----
-- SHARED -- Neutral
|-- SWb Pole 2-----
LIVE -------------- SWb Pole 1 ---------- LIGHT -- Neutral
This would correspond to your
- Red to one terminal
- Black to one terminal
- Second red shared to two terminals by way of a link
The "second red shared to two" would be the live linking to SWa Pole1 and
SWa Pole 2 above.
Using this, when either switch is on the shared fan gets electricity, as
does the switch's own light, but the electricity can't run back through the
other switch to the other light.
If this is the case then I think it contravenes the Regs (a) by the colour
coding - it sounds as though the Black to one terminal is the live to either
the light or fan (b) by not running line and neutral of a circuit in
parallel close together.
It's possible the 'normal' switch with four terminals the other bathroom has
is an INTERMEDIATE light switch, but I don't see how it could be wired the
same way because AFAIK Intermediate switches aren't available in pull-cord.
If the 'normal' switch the other bathroom has is also a bit chunkier (and
maybe a red rocker) than a light switch it's almost certainly a DP switch.
God help you is all I can say, because my head is starting to hurt with the
strangeness of it all :-)
Basic concept of the answer is correct, pretty much as my post further
Not neccessarilly, you can get quite unobtrusively small cieling
mounted 20A pull switches.
Pretty good, You should do more!
This doesn't contravene the regs in any instance. It is perfectly
acceptable to use black as a switch wire as long as it is marked with
red sleeving or similar at all connections. Live and neutral can run
wherever they like, as long as they are connected properly and routed
in accordance with the regs.
As I said, 20A DP clg switches look like normal one's, same size and
Obviously you're not an electrician then!! I've recently finished
wiring 16 fans, 6 speed controllers, 8 automatic changover units all
with varios methods of switching. I could explain how I did that if
| "Owain" wrote:
| Basic concept of the answer is correct, pretty much as my post further
| down! However,
Yes, if I'd waited 20 minutes I could have read your answer instead of
working it out for myself!
| Not neccessarilly, you can get quite unobtrusively small cieling
| mounted 20A pull switches.
Must admit to not having seen those. If I had I might have jumped to the
Which reminds me, to go and screw the bathroom light switch back on the
One minute to tighten the switch and five minutes to clean up the broken
glass from the picture I knocked over taking the torch off the shelf.
| >IE wired something like this (SWa = switch a, which has two poles)
[snip ASCII art]
| Pretty good, You should do more!
Thank you, once it's drawn out it's quite logical.
| >If this is the case then I think it contravenes the Regs (a) by the
| >colour coding - it sounds as though the Black to one terminal is
| >the live to either the light or fan (b) by not running line and
| >neutral of a circuit in parallel close together.
| This doesn't contravene the regs in any instance. It is perfectly
| acceptable to use black as a switch wire as long as it is marked with
| red sleeving or similar at all connections.
Which the OP's weren't. Mind you I suppose *all* his wires should be red,
which would just make things even more complicated.
| >God help you is all I can say, because my head is starting to hurt
| >with the strangeness of it all :-)
| Obviously you're not an electrician then!! I've recently finished
| wiring 16 fans, 6 speed controllers, 8 automatic changover units all
| with varios methods of switching. I could explain how I did that if
| you want!?
It's perfectly straightforward once one understands "oh THAT'S how they did
it!" Just hadn't seen this configuration before. And it was past my bedtime
A normal switch is OK to use, just put the two reds into the COM terminal
and switched live (black) to the L1 terminal. The reason for the double
pole switch being used in the pull cord is beyond me, because the only thing
it is doing is switching the same red on at the same time as the switched
live (black). If the fan continues to run all the time, then you'll need to
move the red that feeds it over to the L1 terminal and have it switch on
with the black.
Find out which red is the actual Feed Live to the switch, then you can mark
it with a pen or pencil to make sure you don't get it mixed up with the
switched red, and then connect it in to the COM terminal of the switch. You
already know the black is the switched live, so this is easy to put in place
on the L1 terminal and get it out of the way as well. Before you connect
the other red to anything, and making sure you don't touch the metal parts
of it, touch against the red in the COM terminal. If the fan begins to run,
then you have it in the wrong side of the switch. This means it is
connected in with black in the L1 terminal.
email@example.com (Nick) wrote in message
you'll have L N and E arriving to the switch
E N and switched live going to the light
E N L and switched live going to the fan.
All you need is a light switch. Check it out with a multimeter with
the mains power off, and if in any doubt, not competent etc, leave it
all well alone.
On 19 Jan 2004 01:54:38 -0800, firstname.lastname@example.org (Nick) wrote:
Sorry, but I hope you haven't rewired as per the other answers.
You need a douple pole switch, usually rated at 20A or similar as used
for immersion heaters.
The reason this type is used is that the fan is shared between two
rooms I would assume. This means in essence that if you connected them
all together as per the other posts then every time you switch the
light on in one room the light in the other rrom will come on. The
douple pole switch prevents this by providing an isolated fan and
light switch on one plate.
When you get your double pole switch you will notice that one pole
will say 'L' and the other 'N'. Ignore this, it isn't a requirement,
more a guide. You need to connect the 2 reds that are looped int the
'L' and 'N' terminals on the 'MAINS' or 'SUPPLY' side.
The red and black switch wires need to go to the two terminals 'L' and
'N' marked 'LOAD', any way round will be fine.
Remember a double pole switch will need a deeper box in the wall than
a normal light swtch.
This is exacly how it is done at my house and I have done the same as
you, moved the pull switch to a wall switch outside.
You don't live round the corner from me do you!
Any more queries, just ask.
Excuse me, but when the double pole switch is closed both ends become live
at the same time. So why not use a single pole switch and connect the
switched live (black) and the other red together ? That way you won't have
to link the two poles together. You're literally making the more expensive
double switch into a single pole one. Seems a bit silly to me. :-))
That's not why it's double pole, it's to prevent the fan switch wire
becoming live from the other end thus livening the light switch wire
if it were directly connected. The way it's wired it will not travel
through the switch as it is on a seperate pole. There will be the same
setup on all other rroms controlling this fan as well.
I've wired loads of fans like that.
Trust me, I do it for a living, if I can't get this right I shouldn't
be doing it!!
Oooohhh !!! I don't like that kind of setup. If I have anything
inter-connected I use a relay to isolate the other switches from the
appliance. That way I know that only one feed is going to the appliance at
a time. The way you talk about would mean that when both switches are on
the appliance is being fed from two points. I don't like that one bit.
Good idea in theory, but you don't get relays and fancy control
systems in houses on building sites. Chuck 'em up I think you'll find
would be the motto! In my defence I never said it was a good way, I
just said I've done it a lot in the past and it works.
There should be, if the house is new enough, a fan isolator close to
the fan in the loft. The way I have wired them there has only been one
three core and earth going to the fan, all the connections being made
in the back of the switch. This would certainly confuse any DIYer
taking the plate off!!
It's not really much different from two or three way lighting
circuits, the live can be passed through the circuit in different
ways, i.e. all wires are designated 'live' but aren't neccessarilly
live at all times and not always fed from the same direction, but once
the correct fuse is pulled it is all safe anyway.
Or have you installed relays on all your 2 way lighting as well? ;-)
I've always put isolator relays beside, or on, the remote appliance so it is
fed from only live at a time. For two, three or more way lighting there is
only one feed at a time going to the light fittings because of the switching
configuration allowing only one path at a time to become live, so the need
for relays isn't an issue in this type of installation. For a remote
appliance that can, and is, being fed with more than one live conductor to
its live terminal, and from more than one switched point all in different
places in the house, then I think it safer to use local relays at the
appliance to take the other feeds away from it directly. The cost of relays
and a box to site them in can't surely be an issue because they're the same
price as a single pole switch and back box.
It's not that I'm disagreeing with you, I can see where you're coming from,
I just know that you won't get this in new houses. It becomes too much a
maintenance issue otherwise. If you know what you're looking at wwith
regard to an electrical installation relays and such like aren't
neccessary. Unfortunately thats the way the industry is, no-one HAS to do
anything a particular way, and often gets done any old how. I'm quite happy
with my way of doing it and you yours, there's no right and wrong in these
two methods, just the usual way and your way!
Oh I believe you, because those are the installations I'm commonly sent to,
to make them safe after the DIYer has done something nasty to themselves
when they tried to fix it. So I know it goes on and I still don't like it.
Gentlemen, thank you all (esp. Lurch aka SJW) for sharing your
knowledge. Yes the fan is shared and the 'immersion switch' rings a
bell as regards what was (professionally) fitted to the other bathroom
(which shares the fan). I knew the new switch had something to do with
boilers :o) I now have the info I need to complete the job.
SJW, I am in Bournemouth as you asked, but want to do this myself. If
I get stuck I will certainly drop you a line. Cheers
I'm not quite sure what the OP meant by shared extractor fan but I'm hoping
to do something similar. I understand how the system works with switched
live running the light and switched live + unswitched live running the
extractor fan (with the unswitched live used to power the fan after the
switch is turned off).
I can appreciated the suggestion for a double pole switch instead of simply
splitting the switched live on the output side of the switch to the fan &
light but a 20A rating seems rather OTT for a 100 watt bulb plus small
"Rob Nicholson" wrote
| > The reason this type is used is that the fan is shared between
| > two rooms I would assume.
| I'm not quite sure what the OP meant by shared extractor fan but
| I'm hoping to do something similar. I understand how the system
| works with switched live running the light and switched live +
| unswitched live running the extractor fan (with the unswitched
| live used to power the fan after the switch is turned off).
If you pull up my ASCII art earlier in the thread, the two Lives going in to
the fan (one from each switch) would go into the Switched Live or Trigger of
your over-run-timer. You'd need a separate run of Permanent Live to the Live
of the fan.
| I can appreciated the suggestion for a double pole switch instead of
| simply splitting the switched live on the output side of the switch
| to the fan & light but a 20A rating seems rather OTT for a 100 watt
| bulb plus small extractor fan?
It's what's available
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.