Gas fire vents

[ronedad]

The draught coming from my living room vent almost cancels out the heat coming from my living room fire. I have a large open plan room approx. 720x390cm(24x13ft). My gas fire is a Baxi PW5 deluxe,with a51/5 backboiler. The gross Heat Input for the fire is given in the tech/spec as 4.67kw. Armed with this info. can anyone tell me if an air brick type vent in a 9in solid brick wall ,measuring22 x16 cm, and having a plastic fascia fitted on the inside permanently open, is the regulatory size required,and I must keep wearing my thermal vest when sitting by the fire! The tech. does mention the vent standard as BS5440 Pt2, and gives some measurements as 70.77cm2 (11in2),which I cannot equate to above. Any help? Before I run out of vests.

 

[twgas]

You need the vent because the boiler that is behind the fire takes loads of air to burn the gas properly. 70 sqcm sounds about right.

 

[tamz]

The input of the fire AND the boiler will determine the ventilation required. To work it out it needs 5cm2 for every kw net input above 7. Not sure the exact input for your boiler, it will be on the data plate of the boiler of if you have the MI's, shown there. With Baxi back boilers the 51 meant 51000btu output.

As an example
Boiler net input 17kw - 7kw = 10 x 5cm2 = 50cm2 vent (5000mm2) of effective free area as measured (the gaps in the vent NOT overall vent size)

To avoid unnecessary draughts use one of these (core drill one is NOT suitable)

http://www.stadium-ventilation.co.uk/vents/downloads/Blackhole_BM720.pdf

 

[namsag]

If your getting too much of a draft you can fit a blast cover if its a stadium orange/red plastic brick outside . have a look on stadium site

Or you could change it to a blackhole vent which is meant to stop drafts by use of baffles inside

 

[rego]

tamz wrote

The input of the fire is irrelevant here

i think not. the input of fire has to be added to that of back boiler before taking off the 7kw

 

[tamz]

tamz wrote

The input of the fire is irrelevant here

i think not. the input of fire has to be added to that of back boiler before taking off the 7kw

You are totally correct, my mistake

 

[kirkgas]

gentlemen lets get back to basics, a terracota air brick is not a suitable means of supplying combustion air to a gas appliances, it is not sleeved for a start, ( i know OP says solid wall) but is OP looking at big or small holes in the vent) , 40 square holes at 10mm = 40cm2, but if the holes are actuallt only 8mm this drops down to 25.6cm2, OP you need to get EXACT HI of boiler and fire, both bits of info available from the tinternet if you dont have the MI, as it is an old appliance it will be quoted as ??Kw HI, two things, 1)you need max HI of boiler + fire, 2) this will be gross so divide the total by 1.1 the - 7 then x 5 =cm2 Free Air, if you have the MI the Free Air is clearly indicated, just take care to ensure you have the correct figure based on boiler and fire, Stadium do a range of vents that have baffles in them to allow free air in but minimise "draught"