Back Boiler Vent

[davek1970]

I have been told that I need a air vent to the outside due to the fact that I have a back boiler and gas fire fitted.

Please can someone confirm how you work out the size of the vent and also should it be positioned high or low in the wall.

Many thanks

Dave

 

[baxpoti]

Do you know what Carbon Monoxide is ?

 

[STEPH-58]

You would need to know the make and model to figure out the vent size you need but assume that it would be 100cm2( about a 5 inch core drill usually works) as to high or low, it doesn't matter as long as you don't block it up .

steph

 

[ChrisR]

You can also have them fitted in the floor if you have a ventilated suspended (wooden) floor.

[deletion]
Some vents are clever with internal baffles which mean you feel less draught. "Draughtbuster"

I would recommend you fit a CO alarm too. Not the sticky patch indicator variety.

 

[baxpoti]

If you have a wall vent it needs to be below a height which I can't remember, I think it's 500mm. (Fire risk thing)

Interesting

Anymore info on this ChrisR

 

[sooey]

If you have a wall vent it needs to be below a height which I can't remember, I think it's 500mm. (Fire risk thing)

Interesting

Anymore info on this ChrisR

Isn't it for internal walls to try and stop the passage of smoke, I think it's 450mm

 

[Prof.plumb]

To calculate the size you need you must establish (as mentioned) the kilowattage of the appliance. So for instance if it were 20kW you would take 7kW off for adventitious air and times that sum by 5 to give you 65 cm2 free area you require. You will more than likely find that on the data badge of the appliance it will state probably 40 or 50,000 btu. To convert from btu to kilowat you divide by 3412 i believe. so a 50000 btu boiler would be 14.65kW so you would require 38cm2 free area.
I imagine these figures will be rectified by some intelligent know it all but these are sum rough guidelines for sizing.

 

[ChrisR]

Isn't it for internal walls to try and stop the passage of smoke, I think it's 450mm

Yes, you're right I was wrong. Head full of fireproof compartments, Industrial etc.

Vent should be away from where people are likely to object and block it up. Near the appliance, at high level (including IN the ceiling, with caveats) or with air-directing louvres are approaches which might achieve the objective.

 

[ChrisR]

14.65kW so you would require 38cm2 free area

You were going fine up til then, but you've not mentioned that the net input of the fire has to be added to that of the boiler. A fire usually uses up the adventitious ventilation, as we know. SO it's probably back to around 75cm sq.

Davek get a corgi to look at the place - if you have other appliances, extractor fans etc things may be different and will need testing.

 

[Prof.plumb]

Yep sorry! If it does not state net input you must divide the gross input by 1.1.

 

[sooey]

Isn't it for internal walls to try and stop the passage of smoke, I think it's 450mm

Yes, you're right I was wrong. Head full of fireproof compartments, Industrial etc.

Vent should be away from where people are likely to object and block it up. Near the appliance, at high level (including IN the ceiling, with caveats) or with air-directing louvres are approaches which might achieve the objective.

Can I have another gold star then Chris, I'd have two then and be well on me way to a big smiley face.

 

[ChrisR]

On yer bike, mate.
Now where was that - oh yes.....
ScouseronaBike

 

[baxpoti]

Depending on the model, 90cm² minimum directly to outside.

 

[gas4you]

Stadium 5" core vent kit is the easiest I find to fit. Gives 100cm2 un-restricted.

 

[namsag]

Venting to underfloor not recommended now due to possibility of radon gas entering property