Installing extractor fan in bathroom

[tomc89]

Hi all,

New to the forum, please be gentle...

My bathroom currently does not have an extractor fan. There is a vent in the top corner of the bathroom which leads to the exterior, but there are no cables in the vicinity to connect an extractor fan to.

In my head, the idea would be to remove the plastic vent covering, fit an extractor fan into the hole already provided, and then wire this into the light. However, I am not really sure where to begin. I've added a few photos below to give some context.

 

[Murdoch]

If you don’t know where to begin then maybe consult a spark

Adding an extractor fan is a good idea but loads of cheap ones are rubbish

Also make sure the gap under the door is at least 6mm so dry air is drawn into the room

 

[SPECIAL LOCATION]

Hi all,

New to the forum, please be gentle...

My bathroom currently does not have an extractor fan. There is a vent in the top corner of the bathroom which leads to the exterior, but there are no cables in the vicinity to connect an extractor fan to.

In my head, the idea would be to remove the plastic vent covering, fit an extractor fan into the hole already provided, and then wire this into the light. However, I am not really sure where to begin. I've added a few photos below to give some context.

I can't tell from your images how big that existing vent is?

But it looks pretty close to the ceiling and if it is an upstairs bathroom with easy access into the loft void, it should be relatively easy job for a competent person.

However, some of the things you need to consider are:-

A standard bathroom fan typically has a 100mm diameter vent duct, with a body that is around 150mm to 160mm square.
Your existing vent looks oblong in shape, so it may not be a simple swap over, without some decorating needed?

You also need to think of how you want the fan to operate?
Some come on with the light, others have a separate switch.
Some are only on whilst the light / switch is on, others have a run-on timer to keep the fan operating after the switch has been turned off.
e.g. continues to run for several minutes after you leave the bathroom to remove moisture and/or odours.
Some have humidity controls to automatically operate as the air moisture levels change.

If you do have a fan with a run-on timer, you may also want to be able to turn if off at times, as a fan motor can be quite a nuisance late at night echoing through a quite house, if you only popped into the bathroom to clean your teeth. (or other short visits!).

Basically, you need a good concept of the wiring requirements for permanent live, switched-live, neutral & earth relating to the existing light fitting & switch.. then which wires you need to extend, via any switches you desire, to the type of fan you have selected.

If the fan location is within a certain distance of a bath or shower then to comply with current wiring regulations, it must also be a 12v supply, not 230v.
As this is an addition to a circuit it should also be correctly designed, installed and tested with test results documented on a minor works certificate to confirm it complies with current wiring regulations.
And if your existing circuit does not have RCD protection this should also be included during the alteration.

Additionally, as Murdoch has mentioned, to extract air from a room, there must be sufficient capacity for replacement air to enter the room. otherwise, any fan you install will never work efficiently.

e.g.
a 100mm diameter duct has an area of approx 7855mm squared. So, if the bathroom has a typical 760mm wide door, then a gap just under 10.5mm is required to let the same volume of new air enter the room that a 100mm duct will allow to leave the room.
(The build-up of mould due to poor ventilation is a common problem in bathrooms with extractor fans, but plush landing carpets blocking any ventilation under the bathroom door).

There are many solutions to your problem, but the key point is how do you want your fan to work?
Once you know that you can select a suitable model and then figure out what wiring alterations are needed for the fan you want to install.

Hope that helps and hasn't confused you even more!?

 

[Luckyboy]

A suitable 230V extractor fan may be installed both in zones 1 and 2, and outside the zones. If the extractor fan is installed in zone 1 or 2 it must be protected against the ingress of moisture to at least IPX4 and be suitable according to manufacturer’s instructions. Regulation 701.512.2 requires that equipment exposed to water jets (for example, for cleaning purposes), shall have a degree of protection of at least IPX5.

An extractor fan supplied from a lighting circuit for a bathroom without a window should have its own means of isolation, as otherwise replacement or maintenance of the fan would have to be carried out in the dark.

An isolation switch for a fan with an overrun facility will need to be triple-pole (switch wire, line and neutral), and must be installed outside zones 0, 1 and 2.

 

[binky]

It's probably easier to vent via the soffit than use that existing hole

 

[tomc89]

I can't tell from your images how big that existing vent is?

But it looks pretty close to the ceiling and if it is an upstairs bathroom with easy access into the loft void, it should be relatively easy job for a competent person.

However, some of the things you need to consider are:-

A standard bathroom fan typically has a 100mm diameter vent duct, with a body that is around 150mm to 160mm square.
Your existing vent looks oblong in shape, so it may not be a simple swap over, without some decorating needed?

You also need to think of how you want the fan to operate?
Some come on with the light, others have a separate switch.
Some are only on whilst the light / switch is on, others have a run-on timer to keep the fan operating after the switch has been turned off.
e.g. continues to run for several minutes after you leave the bathroom to remove moisture and/or odours.
Some have humidity controls to automatically operate as the air moisture levels change.

If you do have a fan with a run-on timer, you may also want to be able to turn if off at times, as a fan motor can be quite a nuisance late at night echoing through a quite house, if you only popped into the bathroom to clean your teeth. (or other short visits!).

Basically, you need a good concept of the wiring requirements for permanent live, switched-live, neutral & earth relating to the existing light fitting & switch.. then which wires you need to extend, via any switches you desire, to the type of fan you have selected.

If the fan location is within a certain distance of a bath or shower then to comply with current wiring regulations, it must also be a 12v supply, not 230v.
As this is an addition to a circuit it should also be correctly designed, installed and tested with test results documented on a minor works certificate to confirm it complies with current wiring regulations.
And if your existing circuit does not have RCD protection this should also be included during the alteration.

Additionally, as Murdoch has mentioned, to extract air from a room, there must be sufficient capacity for replacement air to enter the room. otherwise, any fan you install will never work efficiently.

e.g.
a 100mm diameter duct has an area of approx 7855mm squared. So, if the bathroom has a typical 760mm wide door, then a gap just under 10.5mm is required to let the same volume of new air enter the room that a 100mm duct will allow to leave the room.
(The build-up of mould due to poor ventilation is a common problem in bathrooms with extractor fans, but plush landing carpets blocking any ventilation under the bathroom door).

There are many solutions to your problem, but the key point is how do you want your fan to work?
Once you know that you can select a suitable model and then figure out what wiring alterations are needed for the fan you want to install.

Hope that helps and hasn't confused you even more!?

The existing vent is 170 x 250 on the interior, and 210 x 210 on the exterior...it's a ground floor bathroom but a single storey extension so nothing above it. In terms of access, I can't find a route in without having to cut through from the inside of the bathroom unfortunately, so some patch repair will have to happen I think. With a hole that size, would it potentially be easier to fill this one and create another?

I think in terms of what type of extractor a run-on timer is preferable, the bathroom is far away from any sleeping areas so having an isolator is not really needed for quality of living purposes, but would I need that for regulatory reasons?

 

[Luckyboy]

The existing vent is 170 x 250 on the interior, and 210 x 210 on the exterior...it's a ground floor bathroom but a single storey extension so nothing above it. In terms of access, I can't find a route in without having to cut through from the inside of the bathroom unfortunately, so some patch repair will have to happen I think. With a hole that size, would it potentially be easier to fill this one and create another?

I think in terms of what type of extractor a run-on timer is preferable, the bathroom is far away from any sleeping areas so having an isolator is not really needed for quality of living purposes, but would I need that for regulatory reasons?

It's generally good practice to fit a 3 pole isolator (Line, Switched Line, Neutral) for a new fan installation. Some people will put a fan in without isolation switch, but that prevents anyone from isolating quickly in case of emergency/nuisance/maintenance without switching off the entire lighting circuit.

 

[Geoff1946]

IF (big if!) all the connections you need are available at the light fitting, i.e. live as well as switched live, then it can be wired from there.

For minimum destruction, work out which way the rafters run, and if locating a fan at the end of the same void which houses the light is acceptable, you could cut a square hole in the ceiling close to the fan location, fish a cable through and fit a dry lining box for a fan isolator. Cut a new hole in the wall for the fan, and Hey presto - you don't have to redecorate
Several IFs, but all plausible. You must respect the zone rules for a mains fan. If you need to use a low voltage fan then it all gets more complicated because you have to install the transformer unit too.