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Posted by Noon-Air on October 4, 2008, 7:54 am
> Have a house that was converted into a 3 family about 20 yrs ago. The
> first floor apt heating system (gas, forced air) is running off the
> furnace that used to heat the whole house. (The other two apts have
> their own heating systems.)
> My problem is that their return air for this apt is drawn from the
> common hallway so it is really not returned air. Nor is there a vent
> sending heated air into this hallway. I would like to put in a return
> air in each room that receives hot air and leave the hallway
> unheated..
> If I do this I have an opportunity to shorten the trunk significantly.
> Is there a good reason to have an overlength trunk? The trunk
> originally went outside the house at one time to draw in fresh air and
> there will be / is about 20 excess ft of trunk.
> I am thinking that for the new returned airs I can use flexible
> ducting?.....if I get square inches of the ducts sending heated air
> into the apt I can only get about 75% of that area as return. I
> understand that this will mean a velocity difference. Any problems
> associated with this?
> This is an interim fix...will be replacing the furnace next year.
> Main thing now is to help with keeping heating costs down and not do
> anything detrimental to the installation of a new system.
> Bill
Do the manual D calcs and get back to us.....If you don't know what that is,
then hire somebody that does know.
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> first floor apt heating system (gas, forced air) is running off the
> furnace that used to heat the whole house. (The other two apts have
> their own heating systems.)
> My problem is that their return air for this apt is drawn from the
> common hallway so it is really not returned air. Nor is there a vent
> sending heated air into this hallway. I would like to put in a return
> air in each room that receives hot air and leave the hallway
> unheated..
> If I do this I have an opportunity to shorten the trunk significantly.
> Is there a good reason to have an overlength trunk? The trunk
> originally went outside the house at one time to draw in fresh air and
> there will be / is about 20 excess ft of trunk.
> I am thinking that for the new returned airs I can use flexible
> ducting?.....if I get square inches of the ducts sending heated air
> into the apt I can only get about 75% of that area as return. I
> understand that this will mean a velocity difference. Any problems
> associated with this?
> This is an interim fix...will be replacing the furnace next year.
> Main thing now is to help with keeping heating costs down and not do
> anything detrimental to the installation of a new system.
> Bill