Wire a fan to a separate controller in bathroom

[dgardn2013]

Hi,

I had a fan installed a few months ago, which turns on and off with the light. The plan was it would sort the mould out in the room, and it did for a time but started creeping back. I want to install a purpose fan controller/switch which includes pir and run on timer functionality. The switch doesn't require a switched live.

Can i connect a junction box in the loft to where the light switch currently terminates, then wire out of the junction to the light switch, and then to the pir switch? There is a window in the room, and the ceiling where it would be positioned is a good 9 maybe 10 foot high. Because there is a window i was hoping i could do away with the need for an isolation switch, so there was know way of turning off the fan on purpose or accidentally. The property is 140 years old, so condensation has been an issue in the past before i upgraded the ventilation. I have done 2 very rough diagrams, one incorporating an isolator switch, and the other im hoping will be ok since there's a window in the room. All the wiring is up to part P, i had a consumer unit fitted a few years back, and NICEIC signed it off as well as my property was chosen during the contractors audit.

Cheers
Darren

Untitled

• dgardn2013
• 14 May 2013
• 1

Untitled

• dgardn2013
• 14 May 2013
• 1

 

[PrenticeBoyofDerry]

You will require isolation for safety and maintenance.
You can purchase pir ex-fans.
motion sensor ex-fans
But you could consider the humidistat fan, that will detect moisture levels and then operate when the limit in the room has been detected.
humidistat

 

[bernardgreen]

One reason why fans fail to stop mold is lack of means for replacement air to enter the room to replace the air that the fan has removed. A gap under the door is often enough.

Also they can only remove moisture that comes from use of bath and shower. If the persistant mold is limited to a small area of the wall or ceiling then the cause may be damp from other sources, leaky roof, damp walls, etc etc and an extractor fan will not cure these problems.

 

[dgardn2012]

The fan was installed by a professional contractor, who assessed the condensation first. They also installed a couple more vents in other rooms which has cured all signs of mould else where. The bathroom door is a bi fold type, so there is a gap above and below the door. I think the problem is my tenants dont want to leave the light on for 5-10 minutes when they have finished in there. They are leaving soon, and i have been looking at ways the new tenants dont have the option of disabling it. Its currently wired to the rose, to switch on and off with the light. Cheers

 

[ban-all-sheds]

The most powerful fan in the world will not dry walls which are made wet by spray or splashes - you'll still get mould from that.

 

[dgardn2012]

The mould is no where near as bad as it was, thats why im thinking they dont leave it on long enough. During spring and summer, the fan will most likely only get used after dark. The property is on a hill so it gets plenty of light. Would any of the pictures, conform with regulations? If i wired in a 3a fcu, would an unswitched version be ok. I could get one with a light and check every time i visit the property to make sure it hasnt been removed.

 

[PrenticeBoyofDerry]

The most powerful fan in the world will not dry walls which are made wet by spray or splashes - you'll still get mould from that.

Unless you actually clean down and dry of walls after use.

 

[dgardn2012]

I know any wiring additions in specialised areas needs to be certified and building control notified. I was hoping to run the cables etc where they needed to be, then get a spark to connect and test. A lot of the work is taken out of the equation the, and hopefully work out cheaper then. But i would need to know which diagram would be the way to go. The isolator will be in the utility cupboard that adjoins the bathroom, so 2 cable runs would need to be routed from there, to where they will need to be. Any help with this would be great, i have in the past done spurs etc from sockets. I know i could do it, ones i did past all inspections and safety tests. But because its in the bathroom and regulations, doubled with the fact i'm renting the place out. I have been looking into getting a spark in today. Cheers

 

[viewer]

The earlier comments on need for isolation and humidistats cover the way you need to go electrically.
Unfortunately your underlying problem needs a bit more investigation. Mould is generally linked to condensation not wetted areas per se (it's a complicated energy transfer thing). Condensation is linked to dew point and humidity. Thus it is quite easy to over ventilate and cause surface cooling, especially of wetted areas which then causes condensation on the wet areas rather than drying . This sounds crazy but that's physics. Furthermore, the total airflow through the room may be adequate, but because the air enters via the top and bottom of the door, there will be "dead spots" with little air movement and over-cooled areas.
Most importantly, you should not advise tenants to leave the bathroom door open after use to avoid this situation as this often leads to movement of moisture laden air back into the house where condensation takes place on or in (intestitial) components such as ceiling boards and causing a serious mould problem.
With some, especially very old properties the problem may be one which is insurmountable using ventilation only or even ventilation and heat. Dehumidifiers may be useful as the latent heat is put back into the room. Many have "clocks" which record the length of running so it is possible to agree the running costs with a tenant.

 

[EFLImpudence]

I manage several properties which have considerable condensation problems with some tenants and absolutely no condensation problems with other tenants.

 

[dgardn2013]

Great thanks. The property is 140 years old, solid brick. The problem was assessed by a surveyor, before getting a professional in to look at the ventilation. I did supply a dehimidifier, but the problem was to great. it had a 10 litre tank, and filled within a 3-4 hours. It appeared the vents that had been in for years were creating stale air pockets. In the living room the vent was above the door, the contractor put one about a foot off the floor on a different wall. The mould hasnt returned in that room. In the bedroom the vent was under the window, about a foot off the floor. They put another on the same wall at a higher level, and the problem has now gone in there as well. I had a dryer vent installed and supplied a dryer for the tenants to use. They were using the rads to dry clothes, since there is no washing line being on the first floor. Since then it solved the problem. The contractor installed an extractor that comes on with the bathroom light switch, but since it started getting dark later the mould is slowly starting to come back in just the bathroom. Im guessing that they arent turning the light on since they can see perfectly fine with it being light outside. so in turn the fan hasnt been working. Thats why im looking at making the fan independant of the light. I did consider swapping it for a humidistat fan, but i have heard that they can be temprimental and remain on for hours if set wrong, and can be influanced by external humidity. Having a 3 pole isolation switch, would mean future tenants could just turn it off. But the control i was planing on was a pir that doesnt require a switched live. And from what i have read the 3 pole isolator is needed in rooms that dont have a window, so no light for servicing the fan. But if there is a window in the room, a double pole fcu would provide surficiant protection. If i get an unswitched one, an anti tamper label can go over all means off access to the fuse, so i will know if they have tried to disable. The fan thats in is suitable for connection to the pir switch as it doesnt require a switched live to run. But other types of fan would still need a switched live to enable the run on timer. The pir switch has a built in run on of upto 15 minutes. Thats why i sarted leaning towards this method.

 

[EFLImpudence]

i have read the 3 pole isolator is needed in rooms that dont have a window, so no light for servicing the fan.

That reason is nonsense as we don't have lights when servicing the lights.
Oh. Inspection lamps.

However, a three pole isolator may be specified by the manufacturer's instructions which must be followed and is useful when a fault develops - to isolate.

 

[viewer]

No doubt your consultant will work it out, but may not be a simple answer. What has worked for a number of houses with which I've been involved is a plenum such as nu-aire or a heat exchanger system. These sit in the loft and push air into a central location, e.g. area outside the bathroom door. The nu-aire is uncomplicated, almost silent, not much more expensive than a good fan and fairly small with very low power consumption although it runs 24/7. I have one in my own house. The heat exchangers need a considerable amount of space due to the insulated pipework and. of course are more expensive.
As said by EFL, some tenants have continual problems. others none. Some it is obviously their lifestyle. Other factors may be surprising. I once mapped a council estate for condensation/mould and there was an almost perfect correlation between orientation of the house (i.e. sides facing sunshine/ prevailing winds) and the amount of mould. Several times I have seen people fit double glazing in an attempt to deal with condensation on walls and, of course, this makes things worse.
Given the age of your house, there are two points to check. Is there a salt concentration in the walls and the type of plaster in the areas affected. Salts can be hydroscopic and a mixture of old, soft plaster and hard modern plaster can give odd results.
Best of luck.

 

[dgardn2012]

There are patches that im 99.9% sure the plaster has salt contamination. The worst affected area is the back bedroom chimney breast. The cindensation made it more apparent. The chimney was pointed and re flaunced, and i had the builder install a couple of air bricks in there. The chimney was leaking quite bad, but where the patches are it doesn't make sense to where the damp patches are. It could be drying out, but its more likely hydroscopic salt i reckon. It seemed odd that myself and several previous tenants have had no problem with mould. Then these were moaning within 2 weeks of moving in, and it was growing up the back bedroom wall and across the ceiling. And got worse as time went on, i think they must be alergic to cold. They claimed they were opening windows, but it was to cold. I did consider a loft mounted heat replacement system. But didnt bother due to the high cost. I had already shelled out considerably on various other repairs, because various things all went wrong pretty much at the same time. For the moment i think the mould problem is under control though for the most part. Whats your experience with humidistat fans? Are they any good and reliable. At the moment i would only want to pay around £20 with a view to spending more on one in the future, should it make a difference. But im worried about it miss firing due to external factors. And i have herd that because of where the sensor is, it wont kick in until after the room has already reached the set humidity level. I have seen a fan controller that has a humidistat, and run on timer functionality. This would possibly have the benefit of detecting the humidity level much quicker as it can be mounted to the ceiling. Thanksu

 

[dgardn2012]

There are patches that im 99.9% sure the plaster has salt contamination. The worst affected area is the back bedroom chimney breast. The cindensation made it more apparent. The chimney was pointed and re flaunced, and i had the builder install a couple of air bricks in there. The chimney was leaking quite bad, but where the patches are it doesn't make sense to where the damp patches are. It could be drying out, but its more likely hydroscopic salt i reckon. It seemed odd that myself and several previous tenants have had no problem with mould. Then these were moaning within 2 weeks of moving in, and it was growing up the back bedroom wall and across the ceiling. And got worse as time went on, i think they must be alergic to cold. They claimed they were opening windows, but it was to cold. I did consider a loft mounted heat replacement system. But didnt bother due to the high cost. I had already shelled out considerably on various other repairs, because various things all went wrong pretty much at the same time. For the moment i think the mould problem is under control though for the most part. Whats your experience with humidistat fans? Are they any good and reliable. At the moment i would only want to pay around £20 with a view to spending more on one in the future, should it make a difference. But im worried about it miss firing due to external factors. And i have herd that because of where the sensor is, it wont kick in until after the room has already reached the set humidity level. I have seen a fan controller that has a humidistat, and run on timer functionality. This would possibly have the benefit of detecting the humidity level much quicker as it can be mounted to the ceiling. Thanks