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Topic Title: Timer fans, requirements
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Created On: 04 December 2009 10:29 PM
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 04 December 2009 10:29 PM
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kermit1202

Posts: 114
Joined: 18 November 2007

does anybody know the requirements for when you have to use timer fan in a bathroom / toilet?
i belive it has something to do with the how much venterlation the room has from windows etc?
 04 December 2009 10:39 PM
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luggsey

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 04 December 2009 11:54 PM
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Rightsparks

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Joined: 13 November 2009

Part F of building regs. I haven't got my book handy, but if I remember correctly, a room containing a toilet without a window must be fitted with an extractor fan with a timed overrun of 15 mins (after the light is switched off in other words). Other than that, I think it's just good practice to fit one wherever there is high moisture content - laundry rooms, bathrooms etc. I think humidistat fans are very popular when you explain to customers how they work.

Hope this helps
 05 December 2009 12:06 AM
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micjamesq

Posts: 777
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Approved Document F

But don't get too excited and learning it off-pat, for the winds of change are afoot WRT Part L and Part F of the Building Regs.

Regards

-------------------------
E & OE
 05 December 2009 11:04 AM
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Paul1966

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You do not have to use a timer fan at all.

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

Anything noted in the Approved Document for Part F is merely a suggestion. As the Approved Documents themselves point out, "There is no obligation to adopt any particular solution contained within an Approved Document if you prefer to meet the relevant requirement in some other way."

However, even if one were to try and follow the guidelines in the Approved Document for Part F, the section is rather vague. Here's the relevant extract, page 18, table 1.5:

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.

For a room with no openable window (i.e. an internal room) the fan should have a 15 minute over-run. In rooms with no natural light, the fans could be controlled by the operation of the main room light switch.
 05 December 2009 12:05 PM
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deleted_1_windycom

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And don't forget to fuse the fan down to the manufacturers spec. which is usually 1 Amp, so many leave it on the lighting circuit breaker at 6 Amps .

Regards, John.
 05 December 2009 12:23 PM
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briandoherty

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You may find in practice that it's just about impossible to convince Building Control or other 'important' bodies that you've met the requirements of the Building Regulations unless you have followed the advice in the relevant Approved Documents.

Assuming the conventional Approved Document compliance route is your preferred method of compliance, then Approved Document F requirements (which don't seem at all vague to me) are as follows :

"1.5 Extract ventilation to outside is required in each kitchen, utility room and bathroom and for sanitary accommodation. The extract can be either intermittent or continuously operating. The minimum extract airflow rates at the highest and lowest settings should be no less tahn specified in Table 1.1a."

Table 1.1a shows for a bathroom a Minimum Intermittent Extract Rate of 15 litres per second, and for Mechanical Intermittent Extract serving a room with no openable window, the fan should have a 15 minute over-run.

-------------------------
Regards,

Brian
 05 December 2009 12:59 PM
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Paul1966

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Joined: 21 December 2004

Originally posted by: briandoherty
You may find in practice that it's just about impossible to convince Building Control or other 'important' bodies that you've met the requirements of the Building Regulations unless you have followed the advice in the relevant Approved Documents.


Depends how willing you are to let the bureaucrats get away with being little dictators I suppose. More people need to stand up to them, or they'll only get worse.

Assuming the conventional Approved Document compliance route is your preferred method of compliance, then Approved Document F requirements (which don't seem at all vague to me) are as follows :


The exhaust rates are clear, but the part about a 15-minute over-run isn't. 15 minutes from when? And controlled how? It doesn't say.
 05 December 2009 02:03 PM
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luggsey

Posts: 267
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Originally posted by: windycom

And don't forget to fuse the fan down to the manufacturers spec. which is usually 1 Amp, so many leave it on the lighting circuit breaker at 6 Amps .



Regards, John.


I have never seen anyone fuse a fan down on a ighting circuit, only a 3 pole isolator fitted?
 05 December 2009 04:16 PM
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sparkiemike

Posts: 1660
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Originally posted by: luggsey
Originally posted by: windycom
And don't forget to fuse the fan down to the manufacturers spec. which is usually 1 Amp, so many leave it on the lighting circuit breaker at 6 Amps .
Regards, John.

I have never seen anyone fuse a fan down on a ighting circuit, only a 3 pole isolator fitted?


You may not have seen it, but read the manufacturers instructions, most the domestic vent axia stuff calls for a 3A fuse. Its a real pain in the wotsit!
 05 December 2009 05:32 PM
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deleted_1_windycom

Posts: 438
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Originally posted by: luggsey

I have never seen anyone fuse a fan down on a ighting circuit, only a 3 pole isolator fitted?


You will have seen it luggsey and not realised what you were looking at, normally see a FCU outside and above the bathroom door.

Take the lighting circuit thru the FCU into the bathroom light and the the fan isolator. Fuse the FCU at whatever the maker says. Can't afford vent axia so my cheapies are at 1 Amp

Regards, John.
 05 December 2009 10:53 PM
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luggsey

Posts: 267
Joined: 20 January 2008

Originally posted by: windycom

Originally posted by: luggsey



I have never seen anyone fuse a fan down on a ighting circuit, only a 3 pole isolator fitted?




You will have seen it luggsey and not realised what you were looking at, normally see a FCU outside and above the bathroom door.

Regards, John.


I have been around long enough to know what I'm looking at...
20 Years as a sparks does that!

Anyhow, a timed fan needs a three pole isolator as I said, which is what I have always fitted.
What I didn't know was a requriement to fit an 'extra' fuse by some fan producers. A quick shifty at Vent-Axia's site reveals it is 'some' models that apparantly require an extra fuse but not 'all' which I find strange?

What's the easy way to do this then, fuse down the supply into the bathroom lights and then into a three pole isolator?
Seems a bit OTT to me!
 05 December 2009 11:32 PM
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Paul1966

Posts: 1538
Joined: 21 December 2004

Originally posted by: luggsey
What's the easy way to do this then, fuse down the supply into the bathroom lights and then into a three pole isolator?


Yes. As both the permanent live and switched feed to the fan need to be fused, a single fuse which also feeds the light is the practical way to do it without the need for two fuses.

Of course, if you adopt the much simpler approach of using a non-timer fan on its own switch it becomes less complex.
 06 December 2009 12:42 AM
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PG

Posts: 204
Joined: 17 October 2011

Originally posted by: luggsey

Originally posted by: windycom



Originally posted by: luggsey







I have never seen anyone fuse a fan down on a ighting circuit, only a 3 pole isolator fitted?








You will have seen it luggsey and not realised what you were looking at, normally see a FCU outside and above the bathroom door.



Regards, John.




I have been around long enough to know what I'm looking at...

20 Years as a sparks does that!



Anyhow, a timed fan needs a three pole isolator as I said, which is what I have always fitted.

What I didn't know was a requriement to fit an 'extra' fuse by some fan producers. A quick shifty at Vent-Axia's site reveals it is 'some' models that apparantly require an extra fuse but not 'all' which I find strange?



What's the easy way to do this then, fuse down the supply into the bathroom lights and then into a three pole isolator?

Seems a bit OTT to me!
 06 December 2009 07:44 PM
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deleted_1_windycom

Posts: 438
Joined: 25 August 2004

Originally posted by: luggsey

I have been around long enough to know what I'm looking at...

20 Years as a sparks does that!



Sorry luggsey, didn't mean to be rude to you

Best Regards, John.
 06 December 2009 08:04 PM
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luggsey

Posts: 267
Joined: 20 January 2008

Originally posted by: windycom

Originally posted by: luggsey



I have been around long enough to know what I'm looking at...



20 Years as a sparks does that!







Sorry luggsey, didn't mean to be rude to you



Best Regards, John.


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