extracted fans and gas flue

Is there a specific reg on the distance a fan must be from a gas flue?

The gas installation manual states 300mm, seems very close to me,

or do I go with the normal 600mm.

Any advice please gentlemen.

I was told during My 17th tuition Steps that a fan that isn't used as part of the fire/flue is not allowed to be used in the same room as the appliance.

AndyGuinness

That was my understanding too , in case the fan starves the gas appliance of oxygen.

Not only that EE, but the drawing of potentially deadly gases across an inhabited room is deemed a no no.

AndyGuinness

Ah yes , good point . ZZ .

Does that rule out a cooker hood in a kitchen where a boiler is also in the kitchen then, surely not?

There must be some reg, ie over certain m3 is okay?

Just looked through Part F but cant find owt

FFS,

so,

we have specs from LA about this.

I could really do with some answer to this,

being told something and in writing is 2 different things,

I suppose I need to start trawling through building regs now....



---------- Post Auto-Merged at 20:59 ---------- Previous post was made at 20:56 ----------

Does that rule out a cooker hood in a kitchen where a boiler is also in the kitchen then, surely not?There must be some reg, ie over certain m3 is okay?

Just looked through Part F but cant find owt

Click to expand...

on reading your post Im finding this harder to believe,

what is being said is we cant have a cooker hood if we have a gas cooker...

I now really really need this in writing,

cos, no offence guys,

but using fletch's logic this is looking like a silly argument for no fan allowed.

Steps

http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADJ_2010.pdf, read page 21

Checked BS 5440

Checked GSIUR

Theres no distance mentioned, if the manufactures state this distance then this will override any of the standards anyway.

The bets guidance is in Part J of the building regs.

What would be wise would be to test the gas appliance(spillage test) with all extraction units running all doors shut etc to ensure satisfactory clearance of combustible gases.

It may be wise to speak to the manufacturer, different appliances will be affected at different levels of volumetric extraction.

If i can dig anything else out i will let you know.

---------- Post Auto-Merged at 21:10 ---------- Previous post was made at 21:06 ----------

Does that rule out a cooker hood in a kitchen where a boiler is also in the kitchen then, surely not?There must be some reg, ie over certain m3 is okay?

Just looked through Part F but cant find owt

Click to expand...

First of all you need to identify what type of flue system is involved, if its room sealed/balanced flue theres no issue anyway.

Does that rule out a cooker hood in a kitchen where a boiler is also in the kitchen then, surely not?There must be some reg, ie over certain m3 is okay?

Just looked through Part F but cant find owt

Click to expand...

Could it be that most boilers these days are room sealed, meaning that they draw the oxygen thats needed for clean combustion through part of the flue system which has two seperate parts. one for the exhaust gases and one for the clean air? a tube within a tube!!

Just found a little snip it in Part II BS5440 -2 commentary states where extract systems operate and may effect the performance of the flue, additional ventilation of 50% of the required will normally suffice.

A spillage test will still need to be carried out for confirmation.

thanks Plumber, gasman was there today and all we could find in the instructions was 300mm from an opening,

rang manufacturer (promax?) and they said 300mm as well.

was just concerned about a specific reg somewhere about it.

Sorry Steptoe, misunderstood, i beleive now you mean distance from a terminal to an opening.

Ok

If its "Fanned Draught" the minimum distance is 300mm regardless of position.

If its "Natural Draught" then distance differs with position and rating of appliance.

Upto 7 KW 300mm regardless

7Kw - 14KW - 600mm above a terminal, 300mm below, 400mm horizontal

14KW-32KW - 1500mm above, 300mm below, 600mm horizontal

32KW-70KW - 2000mm above, 600mm below, 600mm horizontal

Though if this is a open flue appliance the above posts still need to considered, in your instance the appliance is not a open flue, so ignore the above.

A Promax is room sealed and fan draught, so minimum is 300mm

First off all we have to know what type of flue arrangement and what the appliance is, eg boiler cooker etc if it is a boiler then it has been tested by the manufacturer and they will state the requirements for the distances from any vent, extractor, windows , dormer roofs, boundary's & internal external corners of buildings, this must be followed as that appliance has been tested to that specification laid out for that model, the other thing as mentioned is if it is a room sealed boiler then it has no risk of flue reversal with an extractor switched on as the boiler obtains it's air via the balanced flue from outside, if it is an open flued boiler it will take it's air for combustion from that room and vents specifically for the supply of air have been fitted in the premises for the supply for that appliance, if you then introduce a fan this could cause flue reversal which means that the vacuum caused by this fan may draw products of combustion back down the flue into the building causing carbon monoxide poisoning.

So steps we need to know what appliance it is eg make and model this will give us something to work on.

Regards, Mike.

---------- Post Auto-Merged at 20:44 ---------- Previous post was made at 20:27 ----------

Just noticed you said a Potterton promax this is a room sealed appliance drawing air from outside and venting products of combustion via a fan through the centre of that balanced flue so should be 300mm, but always check the manufacturers website, and also remember that fitting a fan in a house with a open flued appliance may need a larger vent for to support the combustion of that appliance.

Mike.

Sorry Steptoe, misunderstood, i beleive now you mean distance from a terminal to an opening.Ok

If its "Fanned Draught" the minimum distance is 300mm regardless of position.

If its "Natural Draught" then distance differs with position and rating of appliance.

Upto 7 KW 300mm regardless

7Kw - 14KW - 600mm above a terminal, 300mm below, 400mm horizontal

14KW-32KW - 1500mm above, 300mm below, 600mm horizontal

32KW-70KW - 2000mm above, 600mm below, 600mm horizontal

Though if this is a open flue appliance the above posts still need to considered, in your instance the appliance is not a open flue, so ignore the above.

A Promax is room sealed and fan draught, so minimum is 300mm

Click to expand...

my problem is plumber,

is a natural opening the same as a forced ventilation opening?

nowhere I can find seems to have any info on forced ventilation,ie, an extractor fan, it just states an opening, is this still correct?

You are extracting from inside the building so you are not sucking any products of combustion from the outside into the house, a flue can be 300mm from an opening window so you are fine to fit a fan.

I am presuming that it is just extracting to exterior if so if i is a 4" vent then pop one of the cheap exterior vents with the flaps on the outside so when it shuts down so the flaps drop back into position ( toolstation) about

mike, it could be 4" or 6" normally,

but sometimes may be as large as 12".

a rule is a rule so to speak.

what sort of fan is it !

my problem is plumber,is a natural opening the same as a forced ventilation opening?

nowhere I can find seems to have any info on forced ventilation,ie, an extractor fan, it just states an opening, is this still correct?

Click to expand...

Is this a positive pressure fan, as in draws air from outside to in?

Not sure what you mean, trying to clarify what the problem is.

Mike, Gas Safe registered Engineer.

---------- Post Auto-Merged at 21:14 ---------- Previous post was made at 21:02 ----------

Need to know the setup exactly:

what gas appliances are fitted, eg makes and models

what fans type of fan extract only to exterior eg cooker hood extractor ??

As I said if it is an open flue boiler or Gas fire then Extractors and tumble dryers can effect these and can cause carbon monoxide poisoning due to flue reversal.

all I need is a reg to tell me how far away I MUST fit an extractor fan from a gas boiler flue, a balanced one at that.

I cannot state if the tenant will install a gas cooker, or a tumble dryer, or any other appliance, I can only work on the fixed appliances that are there at the time of installation,

ie, 1 balanced flue boiler, and one extractor fan,(either 4" or 6", other sizes TBC)

sorry I cant be more specific Mike, thats all I can go off thus far.