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Topic Title: Advice on kitchen extractor fan required
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Created On: 19 July 2012 10:49 AM
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 19 July 2012 10:49 AM
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cesltd

Posts: 124
Joined: 21 January 2009

Hi, I've been asked to install an extractor fan in the kitchen of my local church. The kitchen mostly gets used for making cups of tea. The only suitable outside wall means the fan would be installed next to a gas boiler. I have linked a picture, fan to go on left of boiler:
http://i78.photobucket.com/alb...tos/Boiler/boiler.jpg

The instructions for the Xpelair GXC6 fan I am thinking of installing say the following: 'If installing in a room containing a fuel burning device, which has a non balanced flue, it is the installers responsibility to ensure that there is enough replacement air to prevent fumes being drawn down the flue when the fan is operating up to maximum extract.'

I have no idea what a non balanced flue is, I have also linked a pic of the flue: http://i78.photobucket.com/alb...hotos/Boiler/flue.jpg

Would it be ok to install this fan in this location? Any advice would be greatly appreciated.
 19 July 2012 10:57 AM
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rocknroll

Posts: 8905
Joined: 03 October 2005

That looks like a balanced flue.

If the boiler is a 'sealed boiler' or also known a 'balanced flue' this type draws its air for combustion from the outside and generally the location of the fan has no effect, the only no-no is that if the fan is within 300mm of the flue it must not be a reversible fan and the outlet be fitted with flaps.

Generally the rule of thumb is around 300mm from the 'balanced flue' but in many cases this is not practical and less than 300mm does not really have an effect providing you have flaps on the outlet.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 19 July 2012 11:08 AM
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cesltd

Posts: 124
Joined: 21 January 2009

Yes the outlets on those Xpelair fans do have flaps and I should be able to get it 300mm away from the flue, just.
 19 July 2012 11:10 AM
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rocknroll

Posts: 8905
Joined: 03 October 2005

No worries then, job's a good-un!!

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 19 July 2012 11:20 AM
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AJJewsbury

Posts: 11768
Joined: 13 August 2003

That looks like a balanced flue.

Agreed. Usual types are:

'natural draft' (like the old fireplaces or boilers with just a simple flue pipe that acts like an old fashioned chimney - usually have to go pretty much vertically upwards to work) - combustion air comes from the room and the heating effect causes the updraught to take the nasties up the chimney/flue. Can all go wrong if the air pressure in the room is reduced (e.g. by an extract fan or just the wind being in the wrong direction and a door open!)

Balanced flue - air intake is taken from outside (usually through the wall) next to the flue terminal - so the air pressure is the same on both side (hence balanced) - wind (should) make no difference to things as it would affect the pressure on both sides the same and the heat generates enough draught to get the nasties out. It sealed from the room air, so anything that happens inside doesn't matter. Flue is generally very short (i.e. directly through the wall) and relatively large (usually a big rectangular terminal on the outside).

Fan-flue: The next stage on from balanced flue - again room sealed, but has a fan (usually on the extract side) to make the draught - so the flue can now be smaller, longer and within reason go in any direction (although condensing boilers usually have a requirement of a continuous fall back to the boiler to drain condensate). Usually have a small round terminal on the outside wall, but can go up through a roof. AKA room sealed fan (RSF) flue.

- Andy.
 19 July 2012 09:03 PM
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davidwalker2

Posts: 205
Joined: 29 April 2009

This link:
http://www.acwilgar.co.uk/Boil...%20GCNo.52-476-38.pdf
confirms that the heater has a balanced flue and is a room sealed unit, so no problem about the fan provided it has flaps.

David
 19 July 2012 11:45 PM
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sparkingchip

Posts: 6330
Joined: 18 January 2003

Stop patting each other on the back lads for a job well done

Have a look at this instruction book page ten

http://www.heatingspares247.co...ocs/main/Medway-S.pdf

this suggests that the existing water heater is not correctly installed to the manufacturers instructions.

Personally I would want to have a discussion with whoever takes responsibility for the servicing, repair and safety testing of the water heater before installing a extractor fan in the same room.

Andy
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