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Spin Doctor
07-15-2012, 01:31 AM
In the process of remodeling the basement. One of the things we did to free up space was move the furnace and A/C into the actic. Now comes the question of heating and or colling the baesment spaces. What if I install booster fans in the ducts leading from the former registers (still in place with addition fans to move air back up to the main floor. Would it work and if not why.

darryl
07-15-2012, 02:10 AM
I'm not an HVAC expert, but I see two things- moving the furnace might have changed how efficiently it works for a couple of reasons, and the airflow rates would have changed for each vent.

Some re-arranging could be done with the individual vent settings so that each area is still receiving the appropriate amount of heated or cooled air. Beyond that, if some particular ducts can't flow as much as needed even if the vent is wide open, then you could augment that with a fan. The fan or fans might be wired to operate only when the furnace fan comes on, so the effect of it all is to have the same level of air flow as before, and the same division of air into all the served areas. In essence, the furnace should not see any difference in the rate of heat or cooling extracted from it, and every room served should feel as comfortable as before the furnace was moved.

The furnace should have a proper amount of outside air entering it of course, assuming it's a fuel powered one. Besides that, if it is designed to bring in a percentage of outside air to mix into the heated or cooled air, then you would want to make sure that it can still get that air. Being in the attic is going to change some of those parameters.

Part of your question seems to be whether or not you should use fans to cycle basement air back to the furnace. I know from experience that if you can't get the flow going, you won't be transferring heating or cooling into that area. If the air coming from the HVAC unit is augmented by fans, then theoretically the 'spent' room air is being pushed back to the furnace- either through cold air ducts or through stairways and hallways, etc. I think it's probably safer to augment the airflow out of the unit than to augment the spent airflow back into the furnace.

By the way, I think it's a good idea to vent floor-level air from the basement from time to time. In order for this to happen, air has to come in from somewhere as well- through the furnace outside air intake I would assume, though cracks in windows and doors etc are going to let in lots as well. You just want to make sure you aren't causing exhaust gasses from the furnace to partially enter the building. And expelling basement floor level air helps get rid of heavier than air gasses- it makes a noticeable difference in my basement shop.

winchman
07-15-2012, 02:40 AM
You definitely want to have good air flow in the basement if you're in an area where radon gas is an issue. You may need to take other precautions to deal with radon when planning your project.

oldtiffie
07-15-2012, 03:25 AM
If it were me, I'd have taken the air-fow meter readings at each outley/register as if the system was installed correctly it would have been balanced by use of the balancing vanes in the duct-work.

I'd try to replicate those conditions with the new set-up.

http://en.wikipedia.org/wiki/Air_flow_meter

http://www.google.com.au/#hl=en&output=search&sclient=psy-ab&q=air+flow+meter&rlz=1W1IRFC_enAU360&oq=air+flo&gs_l=hp.1.1.0l4.4599.7434.0.12173.9.8.1.0.0.0.320. 2284.2-6j2.8.0...0.0...1c.TmpvwRZWHsc&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&fp=c5d9ee74cee66099&biw=1920&bih=818

Or better yet, rather than perhaps for-ever trying to "get it right", get a good HVAC "pro" in - before the change and after.

Spin Doctor
07-15-2012, 04:39 PM
We had an HVAC contractor do the install*. In fact they were the ones that recommended the move. The space in the basement is not meant as a primary living space. The only other options are elctric baseboard. Ease of installation vs operating costs. Hydronic. Low operating cost vs high install. And neither solves the A/C issue if it needs to be addressed.

*I have to assume they did all the required calculations

rws
07-16-2012, 08:16 AM
Typically, with an air handler in the basement, the ductwork runs along under the floor and has laterals running off and turn up close to the outside walls at windows with floor registers. Is this what you had? And now, with the AHU in the attic, do you have ceiling registers?

Somehow, somewhere, you'll have to build a chase to get a duct down to the basement. Maybe in a closet, or in the corner of a room.

Spin Doctor
07-16-2012, 10:10 AM
The duct work did run on the bottom of the joists. The reason for moving the furnace was to get the duct work out of the way. What I'm looking at is if it is possible to draw air from the main floor living spaces into the basement using the old registers and exhausting back up to the main floor by tying into the old registers and cold air returns with vents in the basement ceiling