vent on door

[Blackcatgas]

i agree that vents are important, but so is careful calculations!!!!!!
20/1.1-7*5= 56cm2, but this isnt accurate, as i said earlier it depends on what fire front is fitted, guys we are trying to advise the OP here and now confusing ourselves, a 45/4E with a PW5 fire needs 82cm2, but if it has a LFE5 fire it needs 86.68cm2 lets get it right or the poor OP is going to rip it all out an get an electric boiler fitted

doh😱!

i agree that vents are important, but so is careful calculations!!!!!!
20/1.1-7*5= 56cm2,* but this isnt accurate, as i said earlier it depends on what fire front is fitted, guys we are trying to advise the OP here and now confusing ourselves, a 45/4E with a PW5 fire needs 82cm2, but if it has a LFE5 fire it needs 86.68cm2 lets get it right or the poor OP is going to rip it all out an get an electric boiler fitted

*Gross input

like somone has just said vent size (cm2) = (maximum net input in kw-7kw) x 5.*

so if you gas fired back boiler is 20kw:
20kw-7kw =14kw
14x5=70 cm2
a 70cm2 vent is about 100mmx100mm in size, get the correct one from a plumbers merchant.

if the air brick in the kitchen is the correct size needed and of the correct type (any old "hole" wont do) then you only need to put a vent in between the room with the boiler and the room with the air brick, (of 70cm2) if there is three or more vents in series then each vent needs to be increased to be 50% increments ie if you vented from the boiler room into the lounge then into the kitchen which has the outside vents.

Ventilation is very important, dont think that just because it "works" and "has done for years" that it will be ok, it wont one day.

* net input.

 

[plumbdocter72]

hi there ,
i have a back boiler heating system,the gas fitter told me i have no air brick in my sitting room so he told me i would have to put a vent in the door .
should i put it at the bottem or the top of the door and how big should the vent be
yes i know i sould have asked him, but for some reason i didnt.

thanks in advance

if the boiler is in a compartment you will need ventilation at high and low level and you will need ventilalatio from an out side wall as well.

to work out the size you have to take the kw of your boiler eg 20kwx5cm=1oocm2 .As for the door it is eg 20xkw of boiler, bottom and 10xkw top if your ventilation is direct from outside into your compartment you will have to use a different formula hope this helps.

 

[Billy Bob Bob]

that is not correct, when calculation multi appliances (in this instance you treat them as seperate, i know they are classed as a combined unit) you add max HI of all open flued appliances in the room, divide by 1.1 to get to net if required (would prob be required on a BBU data badge will confirm) -7 then *5, so you dont discount a 6kw fire and count just the boiler

unless mi say other wise which baxi do

 

[kirkgas]

unless mi say other wise which baxi do

i might be missing something on this, are you saying baxi say in the instructions to discount the fire and only supply a vent for the boiler? if so why is there different levels of ventilation for 2 different boiler/fire combos (with both fires being below 7kw) or are they quoting specific vent requirements for different fire/boiler combos because they are working it out for us, complying with BS5440 pt2, and using the formula i quoted. ie max HI of (boiler +fire)/1.1-7*5. ie 16.49+4.67 (if using PW5) /1.1-7*5=61.18cm2
the boiler the OP has is a 45/4E which has a HI of 16.49kw, so if i understand you correctly if we ignore the fire the vent is 16.49/1.1*5= 74.95cm2,
i appreciate MI supercedes everything else, so i just want to be clear what BAXI are saying in their MI's
cheers

 

[sas]

Well done mate. Not many peoples know about room size calculations and what type of vent they need or whats the combustion may result in their property. This is why the gas and cowboys never mix 🙂 but still most peoples trust the cheap estimators.

 

[Billy Bob Bob]

i might be missing something on this, are you saying baxi say in the instructions to discount the fire and only supply a vent for the boiler? if so why is there different levels of ventilation for 2 different boiler/fire combos (with both fires being below 7kw) or are they quoting specific vent requirements for different fire/boiler combos because they are working it out for us, complying with BS5440 pt2, and using the formula i quoted. ie max HI of (boiler +fire)/1.1-7*5. ie 16.49+4.67 (if using PW5) /1.1-7*5=61.18cm2
the boiler the OP has is a 45/4E which has a HI of 16.49kw, so if i understand you correctly if we ignore the fire the vent is 16.49/1.1*5= 74.95cm2,
i appreciate MI supercedes everything else, so i just want to be clear what BAXI are saying in their MI's
cheers

this is what baxi technical have told me on several of there bermuda installs,for example a burmuda 401 with a gf fire came out at 66.6 cm2,but i always clarify dependant on model

 

[kirkgas]

this is what baxi technical have told me on several of there bermuda installs,for example a burmuda 401 with a gf fire came out at 66.6 cm2,but i always clarify dependant on model

i think we are talking about the same thing after all, calculating these models work out at this value, i think it is perhaps the way we are describing it, BAXI are not ignoring the gf fire they are combining both HI's as per BS5440 pt2