HVAC duct work for addition

Old 11-14-01, 04:06 AM
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HVAC duct work for addition

I have put an addition on my new home and with the help of some friends, I am doing the work myself. My question is this, "What size of heating duct and return will I need for a 250 sq.ft. addition of a bedroom and connected bath?" I have the space available on my furnace to tap into for new duct runs. I just can't find any information regarding size of duct necessary for room volumes. Any info would be appreciated.
Old 11-14-01, 04:32 AM
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The answer you are looking for is in ASHREA manual "D" You might be able to find it on line or at the library. If you can go to a college library, I'm almost certain you'll find one there.
Old 11-16-01, 05:31 AM
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duct size

As was mentioned in the previous reply, you can find the answers in the Manual "D", but obviously you are looking for a simpler answer. Unfortunately, there is not a simple answer to running ductwork. Having just completed a course in designing ductwork, I can tell you that there is a lot more involved than just connecting ductwork to an existing system. Depending on where the new duct is connected, and the type fitting used for the connection, it can have adverse affects on the entire system. Depending on the floor plan, you may have to install an additional return air duct in the new bedroom. The air from the new duct has to get back to the furnace, somehow. Before you start by trial and error on ductwork, check your local area for a trade school that offers HVAC training. They will have copies of Manual "D"and will probably give you one. You might ask them for a duct calculator. It's a little slide rule that comes in handy. A little study and understanding of ductwork will let you check your entire system and will probably let you fine tune it for better comfort and lower operating costs. It doesn't take long to read the manual, and it's definately worth the time.

I'll try to help any way I can. More info would be helpfull as to type of system and floorplan.

Old 11-22-01, 02:33 AM
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duct add on

try the heating calculator at www.onlinecomfort.com there are many variables do to changing the pressures in the other ducts when you add new. vandykr www.wholesalefurnace.com

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