Bathroom fan: do UK regs require connecting via lighting circuit?

[MisterProzilla]

Hi,

I've just had some electrical work completed in the bathroom; I've recently refurbished the bathroom, replacing the old electric shower with a mains/mixer. I had bought an inline fan and a separate humidistat/run-on timer module with the idea that it could be installed using the old electrical shower wiring; my intention was that the wiring would go into the humidistat then onto the fan, so it's always live (with an isolator if needed), detecting moisture and turning on as needed without needing to switch it on manually via the lights or a separate pull switch.
Instead the electrician has installed it on the lighting circuit, saying that regulations require bathroom vent fans to be wired via the lights. I can't find any info about this -the humidistat is now effectively useless as I have to turn on the lights when I want the fan to run. Does anyone know of these regs and can you point me to them?

I'm in the UK by the way!

Thanks for reading

 

[brianmoooore]

Are you sure it's wired as you say? I would have connected it so that it runs all the time the light is on, plus an 'off' delay afterwards, or when the humidistat is on with the light off.

 

[MisterProzilla]

Are you sure it's wired as you say? I would have connected it so that it runs all the time the light is on, plus an 'off' delay afterwards, or when the humidistat is on with the light off.

Wired the way it is currently, it does work as you say - only when the light is on (and the humidistat module has a run-on timer so it does have the delay). I know a lot of people wire them that way, but I wanted to avoid that so I didn't have to switch the lights on all the time (and didn't have to rely on the kids doing it as well). I would have liked it to have detected moisture and turn the fan on even when the lights were off.

 

[DPG]

Wired the way it is currently, it does work as you say - only when the light is on (and the humidistat module has a run-on timer so it does have the delay). I know a lot of people wire them that way, but I wanted to avoid that so I didn't have to switch the lights on all the time (and didn't have to rely on the kids doing it as well). I would have liked it to have detected moisture and turn the fan on even when the lights were off.

I'm with you. I don't like fans that only work when the light is on. Whether the fan is running or not should not be determined by the light switch. 9 times out of 10 the light is not necessary during BST months.

 

[brianmoooore]

Read what I wrote again. I wrote OR when the humidistat..... The fan should run on the humidistat independently of whether the light is on or off.

 

[brianmoooore]

Whether the fan is running or not should not be determined by the light switch. 9 times out of 10 the light is not necessary during BST months.

That assumes the room has a window. I only wire the fan to the light switch if the room is windowless. If there's a window, the fan gets its own switch with a neon or LED indicator.

 

[DPG]

That assumes the room has a window. I only wire the fan to the light switch if the room is windowless. If there's a window, the fan gets its own switch with a neon or LED indicator.

Yes, I should have said in a bathroom with a window, sorry.

 

[davesparks]

No there is no regulation requiring bathroom extract fans to be supplied by a lighting circuit however it is normal for them to be.

There are some rules about the extract fans being wired so that they come on when the lights are on, this is easiest achieved by having the extract supplied by the lighting circuit.

An old electric shower supply is unlikely to be suitable for supplying an extract fan without modification.

If the fan incorporates a humidistat then it should have been wired with a permanently live supply so that the humidistat can operate, this can be done from the lighting circuit.

 

[Electro-tech]

Does this ventilation work come under Document F Now?

 

[brianmoooore]

Does this ventilation work come under Document F Now?

As far as I know, it always has, but of course Document F changes over time.
Current regs, for a refurb of an existing bathroom, are that if there was no fan before, then there's no obligation to fit one. If there was one there before, it needs to be retained or replaced by one at least as effective.

 

[Dustydazzler]

Most times I connect the fan with the light , but with a lot of posh bathrooms / en-suites I am doing they have dimmers and multiple switching for sets of lights.
So I then lean toward a hard wired fan with either a built in PIR or built in humidistat

 

[DPG]

Most times I connect the fan with the light , but with a lot of posh bathrooms / en-suites I am doing they have dimmers and multiple switching for sets of lights.
So I then lean toward a hard wired fan with either a built in PIR or built in humidistat

Trouble with the PIR method is the fan will kick in every time someone goes for a wee. Wasteful, and also unnecessary wear and tear on the fan.

 

[Dustydazzler]

Trouble with the PIR method is the fan will kick in every time someone goes for a wee. Wasteful, and also unnecessary wear and tear on the fan.

I agree but I offer both options and seem people want the PIR option, they pay the money they make the choice.

Also in reality a PIR fan is only like £90 so if it needs replacing in 5 years its nothing really when you think the about it

 

[DPG]

I agree but I offer both options and seem people want the PIR option, they pay the money they make the choice.

Also in reality a PIR fan is only like £90 so if it needs replacing in 5 years its nothing really when you think the about it

Yeah I'm probably being picky. It's just one of the things that bugs me bathroom fans.

 

[Dustydazzler]

Yeah I'm probably being picky. It's just one of the things that bugs me bathroom fans.

I don't have one in my bathroom , I just open the window

 

[Electro-tech]

As far as I know, it always has, but of course Document F changes over time.
Current regs, for a refurb of an existing bathroom, are that if there was no fan before, then there's no obligation to fit one. If there was one there before, it needs to be retained or replaced by one at least as effective.

So are we expected to fit a fan & test the flow rate & notify the LBC with a cert or is this for larger ventilation systems.
The regs are getting that mad that they have brought out Document O for overheating .

 

[brianmoooore]

Most times I connect the fan with the light , but with a lot of posh bathrooms / en-suites I am doing they have dimmers and multiple switching for sets of lights.
So I then lean toward a hard wired fan with either a built in PIR or built in humidistat

It's a long time since I wired a bath/shower room with just one light, so I either wire the fan with one set of lights (they can just switch on the other set if they don't want the fan) or wire the fan on its own switch with a neon.

 

[LastManOnline]

I don't have one in my bathroom , I just open the window

A far more effective option.Up until relatively recently most standard 4" fans were very poor value for money

 

[telectrix]

I don't have one in my bathroom , I just open the window

common sense beats technology every time.

 

[brianmoooore]

common sense beats technology every time.

Until the technology advances to the point when an open window flows air in one direction only, I'll stick with an extractor fan for at least six months of the year.

 

[telectrix]

Until the technology advances to the point when an open window flows air in one direction only, I'll stick with an extractor fan for at least six months of the year.

simples solution. increase the pressure inside the barthroom/bog so that the airflow is to the outside. a few good farts should sudfice.

 

[brianmoooore]

The 'few good farts' are a major part of the problem, according to my missus.

 

[telectrix]

The 'few good farts' are a major part of the problem, according to my missus.

well, it's just jealosy. women can't fart as much as they can't keep their gobs shut long enough to build up the necessary pressure.

 

[Mike Johnson]

The Manrose remote Humidistat will work even if the light is off, a light can be wired across the off side of the single switch and mains neutral: https://myshop.s3-external-3.amazon...mages.Ventilator-vochtsensor-elektronisch.pdf

 

[LastManOnline]

. a few good farts should sudfice.

I was afraid he had retired? Been missed.
Any disquite about Tel,s state of health can now be fully dismissed.I,m not sure what type of barometer the hospital staff used to gauge his recovery ,but readers on here always knew that when he once again would discuss with gusto the topic closest to his heart (no pun intended.And no ,its not electrics), that we could state with confidence "He,s back!.Normal service has resumed"

 

[telectrix]

still here. new laptop as windoze no longer supporst window 7. buggers. got to get it all working. and as regards my state of health. getting better day by day. long as i caN DRIVE TO THE LOCAL SPAR FOR BEER AND smokes.......

 

[MisterProzilla]

The Manrose remote Humidistat will work even if the light is off, a light can be wired across the off side of the single switch and mains neutral: https://myshop.s3-external-3.amazon...mages.Ventilator-vochtsensor-elektronisch.pdf

That's the exact remote humidistat I bought thinking it should be able to work, as you say, even when the light is off.

I queried it with the electrician - he says that the fan will always work with the light regardless, then run on, until humidity is gone.
I don't know, maybe my expectations were back to front about how they actually work - I thought they woul detect moisture THEN come on, rather than having to be turned on then use the stat to turn itself off. If that's the case then this remote stat is doubly redundant - no point in having the sensor if you have to turn it on manually anyway, and then no point in having the run-on timer if it's going to use the sensor to decide when to turn off.

 

[nicebutdim]

That's the exact remote humidistat I bought thinking it should be able to work, as you say, even when the light is off.

I queried it with the electrician - he says that the fan will always work with the light regardless, then run on, until humidity is gone.
I don't know, maybe my expectations were back to front about how they actually work - I thought they woul detect moisture THEN come on, rather than having to be turned on then use the stat to turn itself off. If that's the case then this remote stat is doubly redundant - no point in having the sensor if you have to turn it on manually anyway, and then no point in having the run-on timer if it's going to use the sensor to decide when to turn off.

The humidistat is a switch that operates when set humidity threshold is crossed.

The humidistat you have bought can be wired through a light switch, to operate when light is switched on and continue to run until overrun timer setting has passed. If set humidity threshold is exceeded it will continue to run until such times as humidity decreases below set threshold.

The above is dependant on a permanent live supply to stat, alongside switched live feed to light. Without that permanent supply, the fan is isn't going to run when the light is switched off.

It is equally possible to wire the stat through a switch completely independant of lighting.

Please note that manufacturer specification for your stat stipulates that it must be fused at a maximum of 3A and wired through double pole isolation (3 pole if wired through lighting).

 

[Mike Johnson]

That humidistat will switch on whenever the humidity reaches or exceeds the threshold set on the dial irrespective of the light on or off, just turn the humidistat dial down until it comes on, you probably have it set too high.

 

[nicebutdim]

That humidistat will switch on whenever the humidity reaches or exceeds the threshold set on the dial irrespective of the light on or off, just turn the humidistat dial down until it comes on, you probably have it set too high.

Read through the OP.

 

[Mike Johnson]

Read through the OP.

Read post 27 it's not working with humidity only, wired the correct way if will turn on the fan if the humidity rises above the set threshold no matter if the light is on or off, probably the humidistat is set too high for it to operate, turning the setting screw should turn on the fan at the lower end without the light.

 

[nicebutdim]

Read post 27 it's not working with humidity only, wired the correct way if will turn on the fan if the humidity rises above the set threshold no matter if the light is on or off, probably the humidistat is set too high for it to operate, turning the setting screw should turn on the fan at the lower end without the light.

Quite possible that it is set too high. When I first fitted one in my own home, humidity was an unknown quantity and a quick search of google saw all manner of reccomendations, most of which involved a fairly high humidity setting due to our often damp weather. In the end I set it as low as possible (think manufacturer's instructions state this was around 60%) and was pleased with how it worked. Timer is set to around 15 min for those times when humidity is low, but humidistat switches on and off exactly as one might expect and you can pretty much predict when humidistat will switch the fan.

 

[Mike Johnson]

I recently re-fitted our shower room and put in the a Manrose remote humidistat, whilst working in the shower room the fan would turn on just purely from perspiration without the light inside the shower being on, room lights on a separate circuit, if I remember correctly I have ours set to 40%.

 

[nicebutdim]

I recently re-fitted our shower room and put in the a Manrose remote humidistat, whilst working in the shower room the fan would turn on just purely from perspiration without the light inside the shower being on, room lights on a separate circuit, if I remember correctly I have ours set to 40%.

Can't be certain about specific humidity, but 60% sticks in my mind.

 

[Mike Johnson]

The settings on the Manrose are from 20% to 90%, I would imagine at 90% it would be permenatley on.

 

[nicebutdim]

Just checked manufacturer's data for the fans I've used and humidity can be set between 60 and 90. 60 seemed realistic and achievable in our climate.
The 20% option you have must be for customers in desert regions.

At 90% the fan would rarely come on, unless the room was filled with steam.

 

[Mike Johnson]

I got that the wrong way around, yes the 20% setting according to Manrose is always on, sorry if that confused anyone.

 

[MisterProzilla]

Read post 27 it's not working with humidity only, wired the correct way if will turn on the fan if the humidity rises above the set threshold no matter if the light is on or off, probably the humidistat is set too high for it to operate, turning the setting screw should turn on the fan at the lower end without

I got that the wrong way around, yes the 20% setting according to Manrose is always on, sorry if that confused anyone.

That humidistat will switch on whenever the humidity reaches or exceeds the threshold set on the dial irrespective of the light on or off, just turn the humidistat dial down until it comes on, you probably have it set too high.

Well, looks like that was it; turned the humidity threshold down to about 50% and the fan comes on without the light!

In my defence, I'm not always this dumb, honestly! The wiring via the lighting circuit thing threw me

Thanks for your help everyone

 

[nicebutdim]

I got that the wrong way around, yes the 20% setting according to Manrose is always on, sorry if that confused anyone.

Had me doubting myself and had to think twice before posting

 

[Mike Johnson]

Had me doubting myself and had to think twice before posting

That's what I did not do.