Extractor Fan Humidistat wiring question

[GlennSpray68]

Hi All ,

just a quick question I have on wiring up a fan with a fitted timer and humidistat.

Am I correct in the following wiring for the fan.

From what I understand , due to the timer and humidistat the fan should have a permanent live supply isolated with a 3 way switch.

My intention was to identify the nearest light or junction box with a live (loop or common), neutral and switched live. Take this to to 3 way switch.

Then using 3 core and earth connect this to the fan at the appropriate terminal.

Am I correct in this method. if not would someone correct me

Many Thanks in advance for any replies

Glenn

 

[SimonH2]

A lot depends on how your lighting is wired. If the permanent live is looped at the light then you simply pick up all that you need (permanent live, switched live, neutral, earth) at the light - then take those through your 3C+E via the isolator switch to the fan.
If your lights are looped at the switch then it's a bit harder and you may have to find cables and break into them to get everything you need.

 

[Mottie]

I have an extractor fan with a timer and humidistat but I had mine wired up differently. I wanted it to come on when there was too much humidity (nice steaming shower) but I didn’t want it coming on every time the light was switched on and blowing all the warm air out (when I was having a bath, or popped in for a quick pee) so I connected a permanent live, neutral and earth to the fan and the switched feed was connected to a separate pull switch in the corner of the room above the wc with an on/off indicator. This way, the fan can be switched on independantly if I wanted to or quickly on and off (which makes the timer kick in) to clear the room when I have my mid-day dump!

 

[EFLImpudence]

An isolation switch is optional and nothing to do with the fan features.

My intention was to identify the nearest light or junction box with a live (loop or common), neutral and switched live. Take this to to 3 way switch.

You do not want a three way switch; it will not work like that.

No switch at all will enable it to work when the light is switched on and then run on with the timer AND to work independently through the humidistat.

Then using 3 core and earth connect this to the fan at the appropriate terminal.

Correct.

 

[ban-all-sheds]

You do not want a three way switch; it will not work like that.

Surely the simple (and common) error of saying '3-way' instead of '3-gang' '3-pole' ?

No switch at all will enable it to work when ...

Do you mean that there is no such switch available, or that if he doesn't have one the fan will work as he wants?

 

[EFLImpudence]

Surely the simple (and common) error of saying '3-way' instead of '3-gang'?

I thought he meant three pole.

Do you mean that there is no such switch available, or that if he doesn't have one the fan will work as he wants?

Not having a switch at all will enable it to work when the light is switched on and then run on with the timer AND to work independently through the humidistat.


Some people seem to get away with saying "No deal is better than a bad deal".

 

[ban-all-sheds]

I thought he meant three pole.

Oh FGS.

Second error now corrected.

Not having a switch at all will enable it to work when the light is switched on and then run on with the timer AND to work independently through the humidistat.

So will having a 3-pole isolator, as long as it is left in the ON position.

Whether he actually needs an isolator is another question.

Some people seem to get away with saying "No deal is better than a bad deal".

As in "No clothes are better than bad clothes"?

Or "No air is better than bad air", says mad astronaut?

 

[GlennSpray68]

Hi All,

Thanks for all your replies , sorry its taken so long to reply. Very long days at work!

Sorry should have said 3 pole switch not 3 way .I wanted this so I could isolate the shower for maintenance/cleaning etc.

To make matters more complicated the fan has T,N,L inputs the T input is shown in the diagram as connected to the L input with an optional on off switch on that input line. The inputs are just N & L to a double pole switch then on to the fan as above.There is no mention of the earth on the instructions. See Image below

I am confused now as I cannot see how the fan is powered up after the DP switch is turned off , to me it seems as all the power is killed when the DP switch is off.

Could I identify the common/loop live and neutral in the circuit , break into it with a junction box , run that to the 3 Pole switch , wire the fan using 3 core and earth, running the common/loop to the T and L terminals and the neutral as normal. I am hoping this would mean the fan would be permanently on but is controlled via the humidistat. unless I kill all the power with the 3 pole switch ?

I am struggling with this as the wiring in the loft is like spaghetti due to there being 4 spotlights and an above sink light. As well as a jacuzzi bath , electric shower and heated towel rail !!. Plus I have to contend with the bloody loft insulation .

I hope that is clear , the fan is an expelair dx100hts.

Many Thanks for any help given.
I really hope someone can explain this to me as I thought I had it cracked and the instructions have thrown a spanner in now .
Glenn

 

[EFLImpudence]

T is for Timer - this controls the fan.
If you want it to come on with the light, connect it to the light switch live.

The triple pole switch is optional and only for isolation; not functional operation.

You can use a junction box to connect -

Permanent Live(loop), Switched Live, Neutral and Earth

but you may just as well connect to the first light - or to whatever that is connected.

 

[GlennSpray68]

Thanks EFLImpudence for your advice made it a lot clearer.
I've cut into the circuit with a junction box wired that to the isolator, looped the permanent live to the second live in the switch and am running the 3 core and earth to the fan , had to stop though as the lights gone and my floodlight decided to not work !(will wire up to the fan friday night after I've got a replacement bulb ! for the floodlight)

Many thanks once again for all your help

Glenn

 

[GlennSpray68]

Morning All , Finally wired up the extractor fan last night as detailed above , now the bloody thing does not switch off ! , just runs constantly.
does anyone have any idea why that would be or what I've done wrong ? I've looped the L1 and L2 connections on the 3 pole switch on the input side to provide power to the Timer (as the wiring diagram states that a switch is optional) , I thought this would ensure the humidistat and timer have power constantly and would allow the fan to come on when it detects humidity in the bathroom.

I have a couple of ideas on how to rectify this situation

1. wire the fan to the nearest light and connect the L and T wires to the switched live(I don't understand how the fan will run after the lights are switched of though, as the poer to the timer will be killed when the light switched off ?)

2. wire the timer input to the light , then when the lights are switched on and off it will act as a switch to the timer.

any suggestions would be very gratefully received as I am p****d of with the damn thing now.

Many Thanks as always Glenn

 

[GlennSpray68]

Hi All,

Just had a thought, if I wire the fan in the following method does anyone think it would work correctly .

Permanent live to L , Neutral to N both wired through the 3P switch, T wired to nearest switched live on junction box to ceiling light(to act as a switch for the timer )

By doing this would the fan humidistat would control and operate the fan and a quick pull on the lights would act as the switch to the timer.

I think the problem is that there is no on/off action for the timer to begin the timed overrun ( Am i correct in this ?)

Thanks again Glenn

 

[Mottie]

I’m no electrician but that sounds to me how the fan was wired in our previous house. Will work as you describe but when you pop in the bathroom for a quick pee on a cold dark evening, switching the light on will start the timer and continue running for some time. In our old house with an extension bathroom, that expelled any warm air in the bathroom and is why I had my one wired different in this house, as in post #3.

 

[SimonH2]

I've looped the L1 and L2 connections on the 3 pole switch on the input side to provide power to the Timer

That will make it run continuously. The T input is supposed to be connected to the light (or some other switched source) to trigger the timer and make the fan run - you've wired it permanently live so it will run permanently.

Permanent live to L , Neutral to N both wired through the 3P switch, T wired to nearest switched live on junction box to ceiling light(to act as a switch for the timer )

That's how is should be wired - but note that the T connection MUST be wired through the same 3 pole switch - that's so that switching off the isolator isolates ALL the connections.
Ideally you'd pick up L, N, and T from the same place and route them to the isolator switch with 3C+E - if things are looped at the light fitting (or a JB) then it's easy, if things are looped at the switch then it's harder.