No returns on 2nd floor

[Westcedar]

Our house has no returns on the 2nd floor. Needless to say the air does not move well and upstairs is 5-7 degrees warmer in this heat. We don't have a good way to run returns to the basement from the 2nd floor. Our technician suggests that he zone the system. The thought is that when the 2nd floor is on but the first is off the pressure will cause the 2nd floor air to travel down the stairs and this draw the hot air downstairs.

Seems reasonable but odd. Thoughts ?

[kangaroogod]

Done all the time. The key is that there is sufficient supplies upstairs to satisfy the cooling requirements. I have zoned dozens of systems and they all work well.

[kdean1]

You won't draw the hot air downstairs. Hot air is lighter than cold air. However you can deliver cold air to the 2nd floor and cool the hot air. The solution is to deliver enough air to the 2nd floor.

[George2]

Done all the time. The key is that there is sufficient supplies upstairs to satisfy the cooling requirements. I have zoned dozens of systems and they all work well.

X2

[George2]

You won't draw the hot air downstairs. Hot air is lighter than cold air. However you can deliver cold air to the 2nd floor and cool the hot air. The solution is to deliver enough air to the 2nd floor.

Also...X2

[vstech]

x3, with a warning...

there has to be enough RETURN to satisfy the airflow requirements of the cooling load.
it can be downstairs, but it'll need to be sized large enough to flow the air, and filter the load.

make sure there is enough for 400cfm/ton of cooling, and 300Square inches of filter area per ton for modern filters.

[firecontrol]

Suggestion: Try first manually shutting all of the downstairs supply registers off and see what effect it has. This "should" give you some idea if the idea/suggestion will justify the money spent.

As others have said, the equipment, no matter the modifications still has requirements that must be maintained for proper operation. If your contractor doesn't do the calculations ahead of time to verify that his modifications will allow for sufficient cooling of the 2nd floor while still maintaining the efficiency and reliability of the system then I would step back and look for other options.

Not done correctly: Restricting air flow in half of the house to "pressurize" the remainder can cause premature failure of the blower motor. Can cause flooding of refrigerant back to the compressor leading to it's early failure. Can cause the indoor coil to freeze up. Can result in excessive electric bills with limited comfort to show for it.

Granted, getting return air duct work to the 2nd floor of a home is not an easy task nor is it inexpensive to do. But, getting the right sized return to the second floor and doing it right will do the best job of cooling that floor. You're looking at spending X amount of money to zone the home verses X amount of money to install 2nd floor returns.

Just to throw another option into the mix. This expenditure could be put towards installing a seperate system for the 2nd floor either in the form of standard forced air or a mini-split system. Just a thought.