What size vent?

[uselessFCUK]

Hi guys

House we've moved in to had a conservatory built over the existing vent four years ago!

We have a Potterton Housewarmer BBU and firefront.

What size vent would I need to fit into the conservatory dwarf wall to comply with legislation, please?

Segment from Potterton manual:

3.6 Air Supply & Ventilation

The ventilation of the room containing the boiler shall include air for combustion and draught diverter dilution. A permanent air vent must be fitted either directly to the outside of the building or into a room or space containing a permanent air vent of the same effective area. The air vent must not enter the room through the builders opening.

The minimum effective area of the air vent required is as follows:-

45 Back Boiler and Gas Fire: 73cm²

55 Back Boiler and Gas Fire: 89cm²

Any air grille and/or duct should be so sited and of a type not to become easily blocked or flooded and should offer low resistance to air flow.

If an extraction fan is fitted in any position which could affect the air supply to the boiler, then a spillage test with the fan running as detailed in BS 5440:1 must be carried out.


I will get in a gas pro as this set-up can't have been seen to in that time. Would hate to think it had and the ventilation overlooked!

Sleeved 100 x 100mm

Thanks in advance

UF

 

[Agile]

IF the details you quote are correct, then you can use another 100 x 100 mm in the outside wall.

I always think that its better to fit about 30% greater area when two air ducts are in series as they will have greater resistance. It surprises me that the manufacturers dont say that.

BBUs do need a proper service at least every year. More often if shaggy carpets or furry pets.

Tony

 

[namsag]

Perhaps its because the manufacturers know better than someone who is just guessing and does not have a clue.

Although a 100 by 100 hole is big enough that is only half of it the openings in the vents must be of the correct size to let in enough air thats why proper gas vents have the free air area printed on them.

5 inch stadium core vent with 100cm2 grills will do it

 

[uselessFCUK]

Perhaps its because the manufacturers know better than someone who is just guessing and does not have a clue

Please, tell me more...



Depends on Free-flow air volume of vents?

 

[spacethegas]

oh do tell him more

 

[uselessFCUK]

oh do tell him more

... and your valued input, please


Thanks in advance of your exceptional knowledge.

UF

 

[namsag]

Useless . the coment was directed to Agile.

And yes the hole size matters as in it has to be big enough but no matter if its well over sized its the free air flow through the vent openings that matters. And the closest avialable size you will prob get to what you req is 100cm2

 

[spacethegas]

follow namsag's advice.
just make sure the vent is sleeved through any cavity.

 

[gas4you]

I agree with namsag, but do I remember correctly that the internal wall vent should be 50% bigger than the required external vent to outside?

 

[sooey]

I agree with namsag, but do I remember correctly that the internal wall vent should be 50% bigger than the required external vent to outside?

I think that only applies if it's vented through more than one room.

 

[kirkgas]

2 vents in series (what OP has here) both would be same size (100cm2) IF vent passage goes through a 3rd wall (or any amount over 2, you would fit 100cm2 vent in outside wall and increase other 2 by 50%
100cm2---150cm2---150cm2---150cm2 etc etc, vents don't keep increasing, any more than 2 and 50% increase is deemed to overcome resistance and vent path to ensure adequate combustion air at appliance

 

[gas4you]