Basement return air in summer, open or closed?

[Hvacmack]

To open or close a return air damper in the basement

Case:
- Typical GTA new construction open basement
- Return air in basement is just a take off with a damper right off the return trunk line at ceiling height
- Cx complains the basement gets too cold in the summer and the bedrooms are not cold enough

I have always been taught that returns like this with a damper should be just barely cracked open in the summer under the rationale that;
- This will encourage more return air to be pulled from.the upper floors and therefore increase the amount of hot air being pulled back to the equipment and thus aid in cooling these higher floors
- An open return in the basement will become the path of least resistance in the return trunk line. Pulling the "warmer" air from the ceiling of the basement (relatively speaking) and therefore only just cool the basement down more and increase stratification.

Recently I've been hearing of contractors adding an additional return in the basement to pull cold air from the basement which then redistributes throughout the house.

To me, this doesn't even seem like 6 of one and half a dozen the other. You can't properly increase conditioning in a space without pulling more return air from that space, period. Seems to me that all this would do is essentially lower your return air temperatures, potentially drop the coil temperature resulting in lower sensible capacity, and reduce the amount of return air being pulled from upstairs.

In my region this is by far the biggest complaint, and by no means is there a perfect solution to remedy it 100%. I want to be as educated on this topic as I can be to deliver the best service to my cx's.

Thanks in advance boys!

[Admin]

Chances are not all bedrooms have a return air.  If they close the door it will never cool like the rest of the house.  Leave the furnace fan running continuously and open the basement return.  This may help pull the cold air out of the basement and move it upstairs.  I would even look at closing some of the basement supply air vents.

[Hvacmack]

A fan that is circulating air during an off cycle is going to evaporate condensate on the coil and in the drain pan and re-introduce that humidity back in to the space, so I dont think I would be recommending that.

Do you have a rebut for closing the return to promote more return airflow through upstairs returns? And yes, almost all the new construction in my area barring custom homes only has central returns so I agree that limited under-cut below the door could negate return airflow, but isnt that along the same line of thought of trying to promote more return upstairs by closing off the damper.in the basement? And wouldn't a return vent at ceiling height in a basement be pulling the hottest air from the space and thus be increasing the conditioning in the basement and exacerbating the problem?

Really appreciate the quick reply mate

[Hgye]

I live in a 2 storey house and stratification is a problem.  What helps me is leaving my fan run 24/7, and closing my basement door. I close off all my supplies in the basement. I don't have any returns down there, but if I did, I would close them. 

[Porcupinepuffer]

I'm in a bungalow in an old home. I just close off all my dampers to my supplies in my basement. Leave my returns alone. The cool air blows harder out the vents upstairs (where the cooling is really needed). What air blows out gets sucked back in by the returns upstairs, and any leftover cooling flows down the basement stairs and also gets sucked in by the return air in my basement. This gives me a fairly good balance of temperatures upstairs and downstairs and my a/c doesn't have to run as long since I no longer keep the basement like a meat freezer.

I never liked the idea of closing off returns and potentially starving the blower with a higher static, this will almost certainly guarantee you a loss in CFM's for what comes out the other side...