I have a 1200cfm system, that was poorly ran through the attic. After adding two upstairs room, I need to reroute. I've been thinking about running a single duct through the middle of the house and feeding upstairs and down stairs off the same main trunk. I read somewhere the registers should be near the outside walls, but with this configuration the would actually be closer to the inside walls. Does that really matter? Can I run it all with flex, or do I need rigid? How can I do rigid myself? I know I will need two 12" round ducts leaving the unit for proper airflow, and I have all the registers/CFM drops/reductions configured already. Also if I install a register direct off the main trunk, without a branch duct. Will it mess up the pressure in the system? Thanks for your help.
2006-11-27 12:01:27 · 5 answers · asked by crimsoninja 1 in Home & Garden ➔ Do It Yourself (DIY)
lets start with the 12" round supplies leaving the unit.....the smallest i have ever seen in my 28 yrs of building is a 18" supply and a 16" main return.....dont install a register direct off of the main, u will loose ur pressure.....u can stay with the main feed as a round flex but it really needs to be around 18" min... then install dampers at every drop to control air flow at the registers...
lic. gen. contractor
2006-11-27 13:35:14 · answer #1 · answered by bigg_dogg44 6 · 0⤊ 0⤋
There are less chilly drafts if the registers are located on the outside perimeter of the house. In the old days, heat registers were central and return air grills were on the outside perimeter. With the advent of forced-air heating the location of both was reversed. If at all possible try to do it the correct way.......
Your 2-12" trunks should work @ 800-1000 fpm. Many mechanical inspectors prefer hard pipe rather than flex duct. One reason is fire spread prevention and the other is less likelihood of future deterioration. Air movement is better in hard pipe.
You might want to try your local library for info regarding installation of ductwork. Or pay a heating guy to consult or do a little moonlighting for you.
Good luck.
2006-11-29 03:02:00 · answer #2 · answered by Huero 5 · 0⤊ 0⤋
You need 6 inch taps. you cut a 6 inch hole in the 10 inch duct then install the tap over the hole. Typically the main line is metal duct wrapped with 2" insulation. Then 6" taps cut into the main line and 6" flex duct run to each boot where the air is then sent into the rooms. Trying to use flex duct for your main line is insane and will ultimately be more expensive. Also, a 10" main is to small for any central air system and will not allow enough air flow. Your ductwork is much more important than you think and should be done right.
2016-05-23 15:48:01 · answer #3 · answered by Anonymous · 0⤊ 0⤋
I think it will work okay. Putting the registers near the outer walls tends to create a more uniform temp all over, but is not required. As far as the one register without a branch duct- not a big issue, you can always adjust by opening or closing it partialy. With remodeling and additions you can't always do the best layout. The biggest concern is that you don't restrict the flow at all.
2006-11-27 12:19:23 · answer #4 · answered by morris 5 · 1⤊ 0⤋
1200 cfm for a two story house is short, the heat in the upstairs along with solar gain from windows your gonna have a problem. I suggest you look to increase your cooling capacity or install a unit for upstairs, problem being the stat for the main unit cant be downstairs or upstairs temp difference to much, good luck
2006-11-27 12:58:41 · answer #5 · answered by edgarrrw 4 · 0⤊ 0⤋