HVAC in basement

Shawnzy · 11-14-2011, 06:49 PM

I am finishing basement bedrooms and adding bath. 1 built around any of the hvac that is ran to vents but the big cold air return extends all the way across the room. I am wondering if I can shorten it to accomidate closet? and the system that runs across to the vents on other side of the house is a 8X24 sytem that is supplying 3 vents. I want to shorten the cold air return and the supply 8x24 into a 8 x 12 supply?

if I didnt explain it properly sorry, Im new to HVAC.

Shawn

Doc Holliday · 11-14-2011, 07:06 PM

Simply shortening a run is not a concern on either end but making the diameter of the run smaller is a serious hazard to your a/c system's health.

Shawnzy · 11-14-2011, 07:33 PM

Ok so I can shorten the cold air return thanks!.. now the big supply is reduced 6ft into the room into the 8 x 12 line... the big 8x24 has 3 runs off of it and where it is reduced into 8 x 12 it has 4 runs off of it? seems kind of odd?

What kind of area can the cold air return be closed into to still efficient to supply A/C system. I want to build a 6ft long by 3ft deep by 6' high closet and hoping that will be sufficient enough for the cold air return so I can tuck it away in closet? I have seen them many times in closets not very big but I dont want to take a chance so im curious.

Thanks Shawn

Doc Holliday · 11-14-2011, 08:09 PM

depends on the size of the system. By closet I'm taking vertical unit on a platform with a big square hole cut out under it to a return air grill (with a filter) on the wall in front of it? Is that right?

Doc Holliday · 11-14-2011, 08:23 PM

http://www.comfort-calc.net/cfm_chart.html

your system needs to move a certain total cfm to be efficient. Each size duct allows a certain cfm to the room it supplies, reducing or deducting from the total cfm supplied by said system until it's all used up.

i don't know what your system size is or what your duct work sizing is like sitting from here.

Shawnzy · 12-05-2011, 08:15 PM

The duct size is 18 x 8. I have some pictures now, I want to shorten the cold air return, and run the 18x8 trunk on a couple quick 45's or 22's whatever I can get my hands on and run it along the wall so I only have to make a small 18inch soffit rather then a 40 inch sofit which kills the space in the room.