I've recently bought a humidistat/timer extractor fan for a bathroom, to
replace a broken (non-humidistat) one (this model:
<http://preview.tinyurl.com/6anlvnq ). However, although I've fitted
plenty of these before, I'm really scratching my head over wiring this
up. I have L, N, and switched L wires feeding it, so it will switch on
with the bathroom lights and stay on for a bit, governed by the timer
(and humidistat as needed). There's a terminal block inside the fan
labelled L, N and LS, but the pre-connected wires don't make sense to me
- there's nothing at all connected to the LS terminal. Seems to me that
it's been incorrectly factory-wired but looking at it I can't figure out
how it ought to be, or whether I should send it back?
I've put a rubbish photo of the fitted fan here:
...and here's a corresponding sketch showing more clearly where the
wires go (note there's a pull cord switch fitted which I'll want to
over-ride anyway). Nothing on the circuit board saying which wires are
Manufacturer's wiring instructions, such as they are, are here (mine
will be fig 4):
It's all a bit awkward because this is in a rented property, ie not my
home; although my tenants are fine about me going round to sort it, I
can't keep on pestering them indefinitely, and need to be able to just
go back once more and resolve it for definite....
Any advice much appreciated
It looks to me as if the terminal block is provided in order to cater
for setups with or without an internal pull switch. The switched live
obviously has to end up at the middle terminal on the circuit board, one
way or another. As shown, it comes from the internal pull switch.
If you remove this switch and use your own external switching, you need
to bring your external L, N and LS wires onto the terminal block, and
the output from LS on the terminal block needs to go to the middle
terminal (yellow wire) on the circuit board.
It seems to me the thing is factory pre-wired as a standalone unit which
does not make use of the switched live you are able to provide. The idea
is you just wire in the L and N, then use the pull switch to fire it up.
Either this switch is momentary action (as opposed to pull-to-switch-on
and pull-again-to-switch-off) so that pulling it once will keep the fan
on for a fixed amount of time, or else it will just stay on for a fixed
time after you pull it again to switch off.
It seems clear that the black wire is neutral, both orange wires are
unswitched live, and the pull switch then makes the yellow wire switched
live, which goes straight to the circuit board. Therefore as far as the
circuit board is concerned, the top terminal is neutral, the middle one
switched live, and the bottom one unswitched live.
I think what you need to do is make the yellow wire go from the switch
to the circuit board indirectly, via the LS terminal in the block, in
exactly the same way as the orange wire already goes from the switch
to the circuit board via the L terminal.
That done, the pull switch is able to *provide* a switched live output
to feed your light if you so choose, or if you are already providing a
switched live from an external switch, the fan unit can accept that as
input. The same wiring will work both modes, the two switches are simply
in parallel, i.e. the lamp (and fan) will come on when *either* of the
switches is on, and will only go off when *both* switches are off.
There is a further operating mode you might like to go for. This involves
rewiring it by leaving the yellow wire alone (going from switch to circuit
board). You also leave alone the orange wire which goes from L to the
circuit board. But the other orange wire should go from the switch to LS
instead of from switch to L. This way, the pull switch will make the fan
come on only when the switched live which you supply is live (i.e. when
you have switched the light on). How it would work would depend on whether
the switch is momentary action or pull-on-pull-off. If momentary, you need
to tug the cord each time you want the fan to come on. If p-o-p-o, the pull
switch will change modes between "fan always off" and "fan comes on with
Woa horse... what timer?
If you have a fan with timer overrun, then you need L, N, and LS. LS
kicks it off when the light comes on, and the internal timer keeps it
going for a user selectable delay after LS goes off using power from L.
With a humidistat fan there is usually no timer. You feed it L and N
(and you can park your unneeded switched live in the LS terminal out of
harms way). It comes on when the humidity reaches the trigger threshold,
and goes off when sufficiently below it.
Now yours has a party trick with a dangly cord. Chances are all this
does is manually turn the fan on, overriding the humidistat (handy for
clearing the air when it ain't steam you are trying to shift!) This type
of switch could be a toggle effect - changing back and forth between on
or off each time you pull it like a light switch (a multimeter on ohms
will soon tell you). The other alternative is the fan is posh enough to
have a timer as well. In which case I would expect mr. dangly to be a
pull to make switch that opens when you let go, and it will trigger the
fan for a timed duration - again overriding the humidistat.
Hence, long and short: connect N to N, L to L, and LS to LS. Set the
humidity setting so its not running all the time. Show the tenants the
string to pull to get rid of whiffs, and possibly remind em to pull it
again if it turns out there is no timer.
Thanks very much for the responses: am happier now! and confident I can
sort it out.
To follow up - it's certainly got an overrun timer in addition to the
humidistat: has to have one, as this is an internal bathroom. There are
two little dials within the gubbins of the fan; one to set the humidity
and the other the time.
Also FYI - I'm definitely removing the pull-cord switch as it can't be
used, as per the instructions (for reasons of geometry/bad design) if
the fan is ceiling mounted, as mine is. Toolstation don't stock a
humidistat fan without the pull cord.
OK, without the pull cord you will lose the timer operation altogether
with the wiring as it currently stands.
If you want to have both "fan on with the light", "overrun after", and
"humidistat control", you will probably need to tweak the internal wiring.
Going by your circus diagram, you might get the functionality you need
by disconnecting the yellow wire from the pull switch, and connecting it
to the top of the LS terminal which was originally parking the LS wire
from the light switch / ceiling rose. Hence turning the light on will
be the same as pulling and holding the pull cord.
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