Are the low/high returns switchable via a damper?

If so, for winter heating, have you tried operating your system with in one instance only the low returns open, and in another instance only the high returns open? And if so, did you notice any difference in comfort levels within the rooms where you did this?

 

Not sure what you mean by damper, but the return vents have a slider on the side that lets me close or open them easily. Here are some pics.

 

It appears set in first photo has high return grill damper closed with bottom open and the other set the opposite way.

Try the following, since it is still the winter heating season: open top return grill dampers and close bottom return grill dampers on all sets like this throughout the home. Run it a few days like that and see if you're comfortable. Then switch positions on each set and run it like that for a few more days. Note any change in comfort.

When summer hits, repeat this test. The results of these tests should advise you which is the best configuration to have the dampers be in winter and summer.

 

Thanks! Will do your test. Is that what they typically have been saying for winter setups for many years? Top open, bottom closed?

I have high ceilings in quite a few places, if that means anything.

 

Dont adjust without proffesional help

 

Most systems are designed so ALL vents remain open all the time...

We have no way of knowing how your system is actually set up.

Warm air rises... So, in cooling season, you want warm air returns, so, high... In heating season, you want cold air returns... So low...

 

You mean in cooling season high returns OPEN, low returns closed, and heating season, low returns open, and high returns closed.

 

That is the general rule... But air mixing may be needed, high ceilings could require both returns...

A professional needs to evaluate what you have and examine how it can be modified.