Extractor fan from light fitting?

[aces86]

Can i take the live and neutral from the light and run it straight to the extractor fan? I just want the fan to turn on with the light. Must i have an isolator switch for the system to work? Installing an isolator is extremely inconvenient due to my circumstances.

To make things more complicated the fan is a timer model so has a switched live connection. Can i use the same live from the light to go in here? Im not bothered about the timer in fact i would rather the fan turns off with the light.

Thanks for reading.

 

[Taylortwocities]

You can connect the live and switched live together in the fan, otherwise it will not work at all.

Re isolator. Does the room have a window?

 

[aces86]

Sounds easy enough then. When i take the feeds from the light fitting, how should i do so? Just cram the wires in there or use a junction box? Is it bad practice to put 2 wires in 1 terminal?

The room does have a window, why do you ask?

I have no knowledge or experience with electrics just a bit of common sense so sorry if im not making sense. I really appreciate your help also, thanks mate.

 

[ericmark]

If room has opening window it does not need a fan so no rules governing it's use but if window does not open then fan can't work on light alone it needs another trigger. I think building regulations Part F! Be also aware of Part P(Electric), Part L(energy conservation), Part J(If any flues in house) and Part M(Switch height).
This

Standard Lighting

• ericmark
• 17 Aug 2008
• 13

Standard lighting diagram

is general wiring diagram. Isolator is really required as fans are not very well made and do fail from time to time and without isolator you have no lights.
If the fan is to satisfy building regs then you need the timer or run 24/7 if your window opens the not a requirement.

 

[Paul_C]

if window does not open then fan can't work on light alone it needs another trigger

There is no regulation which says that anywhere. The "Approved Document" for Part F (which, remember, is not law anyway, only guidelines) says that the fan must be capable of being switched on manually. It doesn't contain any restriction to say that the switch cannot also turn on a light.

If the fan is to satisfy building regs then you need the timer

Again, only a rather vague statement in the Approved Document, which mentions a 15-minute over-run but completely fails to specify the starting reference point or how it is to be controlled.

The only legal requirement is that "There shall be adequate means of ventilation provided for people in the building."

If you have a fan which is capable of being switched on and off at will and provides sufficient airflow when running, then I'd argue with any building inspector that the requirement has been satisfied.

 

[ericmark]

DWELLINGS
Table 1.5 Controls for ventilation devices
Mechanical intermittent extract
Intermittent extract can be operated manually and/or automatically by a sensor (e.g. humidity sensor, occupancy/usage sensor, detection of moisture/pollutant release). Humidity controls should not be used for sanitary accommodation as odour is the main pollutant.
In kitchens, any automatic control must provide sufficient flow during cooking with fossil fuels (e.g. gas) to avoid the build-up of combustion products.
Any automatic control must provide manual over-ride to allow the occupant to turn the extract on.

As to if coming on with light is automatic is open for debate! But I would consider in rooms with natural light at least the switch would need a label!

For a room with no openable window (i.e. an internal room), the fan should have a 15 minute over-run.

OK it does not say from what point but I would think most people would say from leaving room. I suppose a push button that you press on entering would comply but real point is would LABC see it that way?

In rooms with no natural light, the fans could be controlled by the operation of the main room light switch.

I would consider the reverse must also be true as a room with natural light needs control with other than main room light.

Mechanical continuous supply or extract/passive stack ventilation
Set up to operate without occupant intervention (may have manual control to select maximum 'boost' rate). May have automatic controls. (e.g. humidity sensor, occupancy/usage sensor, detection of moisture pollutant release). Humidity controls should not be used for sanitary accommodation as odour is the main pollutant.
In kitchens, any automatic control must provide sufficient flow during cooking with fossil fuels (e.g. gas) to avoid the build-up of combustion products.
Ensure the system always provides the minimum whole building ventilation provision as specified in Table 1.1b.
Background ventilators
They can be either manually adjustable or automatically controlled (see paragraphs 0.17 to 0.19).
Purge ventilation Manually operated.
Accessible controls
Where manual controls are provided, they should be within reasonable reach of occupants. It is recommended that they are located in accordance with the guidance for Requirement N3 Safe opening and closing of windows etc., which is given in Approved Document N. Where reasonable, the use of pull cords, operating rods or similar devices may help to achieve this. Although Requirement N3 only applies to work places, for the purposes of this Approved Document it should also apply to dwellings.

Personally I hate those fans and think an opening window is far better. But LABC inspectors can be rather pedantic at times and not to say what Part F says could lead people to unnecessary conflict. Lets face in most people switch off the isolator and it never runs again once the inspector has left the building. I think the easy way is to ask the LABC what he wants then you can't go wrong.
Except for kitchens which must have automatic control one can have manual control so I don't understand why we have all the complication of linking with lights when a plain on/off switch at entrance would do?
And I have not seen these automatic controls in kitchens! It has just been a switch on the hob. In industry I have set up systems when unless the extractor is running the main machine will not work but never seen anything like that on a kitchen hob?
So it does seem as if only lip service is paid to Part F and the document is really more use as loo paper. But that is not for me to decide. I just tell them what it says it up to those doing the job to if they take any notice.

 

[Johnmelad502]

Don't know if this will be of help to people. I found this on the net and it worked for me.

How to wire an extractor fan

 

[Taylortwocities]

Jonnie, very nice. But you do not need to trawl the net to find info like this.

Many of our regular contributors have gone to an awful lot of trouble to put most of what many folk need all in one place.

Its called the WIKI, its here, on this site and only two clicks away!!

If you go to the forum title (Electrics UK) and click on that its the first thing that you should see.

As a short cut, the fan diagrams and info is here:
//www.diynot.com/wiki/electrics:lighting:fan

Do have a look through the WIKI. Its WIKIED

 

[Johnmelad502]

Jonnie, very nice. But you do not need to trawl the net to find info like this.

Many of our regular contributors have gone to an awful lot of trouble to put most of what many folk need all in one place.

Its called the WIKI, its here, on this site and only two clicks away!!

If you go to the forum title (Electrics UK) and click on that its the first thing that you should see.

As a short cut, the fan diagrams and info is here:
//www.diynot.com/wiki/electrics:lighting:fan

Do have a look through the WIKI. Its WIKIED

The diagram in the wiki is good, the one I posted is much easier for people to associate with. The one you posted (in wiki) is not as detailed as the one I posted, and so for the layman is not as easy to understand.

I have used the wiki many, many times, (it's very good) so please don't point me towards the obvious.

Cheers
John

 

[ban-all-sheds]

The diagram in the wiki is good, the one I posted is much easier for people to associate with. The one you posted (in wiki) is not as detailed as the one I posted, and so for the layman is not as easy to understand.

Feel free to improve the Wiki, rather than plug your own site.

 

[Johnmelad502]

The diagram in the wiki is good, the one I posted is much easier for people to associate with. The one you posted (in wiki) is not as detailed as the one I posted, and so for the layman is not as easy to understand.

Feel free to improve the Wiki, rather than plug your own site.

There is nothing on that link that advertises my site. The diagram is stored on my site but does not link to any other pages on my site whatsoever.

If I had stored it on photobucket, would you have accused me of advertising photobucket?

But thank you anyway for agreeing that the diagram I posted was an improvement one on the Wiki.

 

[ban-all-sheds]

There is nothing on that link that advertises my site. The diagram is stored on my site but does not link to any other pages on my site whatsoever.

The hostname part of the URL is your site.

If I had stored it on photobucket, would you have accused me of advertising photobucket?

No, because Photobucket is not registered to you, and does not make money from providing physical services advertised on their site.

 

[Johnmelad502]

There is nothing on that link that advertises my site. The diagram is stored on my site but does not link to any other pages on my site whatsoever.

The hostname part of the URL is your site.

If I had stored it on photobucket, would you have accused me of advertising photobucket?

No, because Photobucket is not registered to you, and does not make money from providing physical services advertised on their site.

You really are...

 

[Paul_C]

As to if coming on with light is automatic is open for debate! But I would consider in rooms with natural light at least the switch would need a label!

Personally, I wouldn't class that as automatic, since it requires the operation of a switch (albeit a switch which also controls the light) to turn the fan and off. I would class automatic operation as being when the fan is triggered into operation by a humidity sensor, motion sensor, or something similar.

OK it does not say from what point but I would think most people would say from leaving room.

But then you can debate over what triggers that 15-minute period from leaving the room. If the bathroom has no natural light and you link the timer fan to the light switch, then it's reasonable to asume that the light will be switched off as the person leaves, hence the timer period starts at that point. But what if the fan is switched independently, whether the bathroom has natural light or not? If we take it that the 15-minute over-run is supposed to be from leaving the room, there would then be nothing to stop a person blipping the switch on & off as he enters, spending 10 minutes in the bathroom, then the fan will run for only another 5 minutes after he leaves. And seeing as with independent switching (or linked to the light but in a bathroom with its own natural light) there's nothing to stop the person going in there from not switching on the fan at all, the whole "requirement" in the Approved Document seems pretty pointless.

I suppose a push button that you press on entering would comply but real point is would LABC see it that way?

Depends how willing somebody is to capitulate to the council gestapo agent's personal agenda, I suppose. If it were my house I was building, I'd argue all the way that the Building Regs. give them absolutely no authority to demand a timer fan, however it's operated.

So many of these petty demands are stupid anyway. Even if somebody gives in and fits a timer fan set to 15 minutes, do these people really think that home owners aren't just going to take the cover off after the inspector has gone and adjust the timer to something more reasonable, or disable the timer completely?

In rooms with no natural light, the fans could be controlled by the operation of the main room light switch.

I would consider the reverse must also be true as a room with natural light needs control with other than main room light.

That's one more reason why for myself I would always wire the fan completely independently from the light, but even if one were to apply the guidelines in the Approved Document, I don't see anywhere which stipulates that. The only requirement listed is that the fan is operated either automatically or manually, and that if automatic then a manual override should be provided. Nothing says that the manual switching/override cannot also operate a light in parallel.

This leads back to your first point about automatic vs. manual, but in fact I think the Approved Document itself rather settles that question. As it suggests that a timer fan could be operated from the light, and LABC inspectors seem to accept that arrangement, then for the purposes of the Approved Document that must amount to manual switching, surely? If it were to be classed as automatic by virtue of the fan coming on with the light, then there would need to be a separate fan-only override switch.

Except for kitchens which must have automatic control

Where is there anything which says that?

one can have manual control so I don't understand why we have all the complication of linking with lights when a plain on/off switch at entrance would do?

I don't either. Linking a timer fan to the light means that the fan is often running completely unnecessarily when somebody just goes into the bathroom for a minute, and then continues to run equally unnecessarily for several minutes after he leaves. Or in a room with natural light, it means that the light is burning away needlessly in broad daylight if somebody takes a bath or shower and wants to run the exhaust fan. I thought we were supposed to be conserving energy, not wasting it?

So it does seem as if only lip service is paid to Part F and the document is really more use as loo paper.

That goes for 99% of the paperwork the government churns out......