2nd floor of house not being cooled with central air

[brian0918]

We have central air, and the upstairs stays around 85+ (in 100% humidity) despite the temperature downstairs staying at 75 or less (ie, whatever the thermostat is set at). IThe upstairs has two fully-open vents through which little air blows, and what appear to be 2-3 vents for the warm air to exit. Can anything be done to help cool the upstairs? The curtains/blinds are kept closed, and the door leading to the upstairs is kept shut to prevent any warm air downstairs from moving upstairs.

Also, attached to our air conditioning system in the basement is an air cleaner that doesn't work, and when you remove the cover from that, a ton of air is pulled in. I've noticed that this causes a lot more cold air to be forced through the vents, substantially cooling the upstairs. However, we asked someone who would know about these things, and he said you shouldn't do that (for some reason). Any information?

[ameijers]

We can't see your house from here, and I'm no HVAC expert. However, one of the family homes we had when I was a kid had a similar problem, even though the system was 'zoned', with 2 thermostats. Ended up with a 2nd smaller furnace for upstairs, and splitting out the plenum. It all worked fine after that.

I'd recommend paying a HVAC contractor, NOT the one named on the sticker on the furnace, to come out and do an inspection and load calc for both floors, and to balance and tweak the any baffles or valves in the ductwork. The air cleaner sounds like a good place to start as something throwing the existing air flow off balance. If opening the cover improves air flow to upstairs, I'd suspect insufficent air flow from the returns on that floor. If the cleaner doesn't work, and you don't miss it, probably simplest to have the contractor rip it out and plate the hole over. (My furnace in my 'new' 1960 house, with original furnace, has a big plate on the side where something like that used to be... Yes, a new HVAC is on the list, but the new roof comes first.) Try leaving the stairway door open for a few days- if that improves things, that means air return problems are real likely.

aem sends....

[Edwin Pawlowski]

You have air circulation problems. It may be the air cleaner blocking the air flow. I can't see your setup so I can't say if removing the cover is good or bad, but if it is clogged, get it cleared out. You waste a lot of energy that way. Are there other filters in the system? If so, be sure they are clean.

If the filters and air non-working air cleaner is clear, the evaporator coil itself may be clogged.

[Joseph Meehan]

We can't tell from here, but it may be a specific problem like the air cleaner or dirty coils preventing air flow or it may be a bad or damaged duct design. You will need a local pro to check it. Ask around and find a HVAC professional that is recommended and have them check it out.

[CL (dnoyeB) Gilbert]

1. get cleaner fixed.
2. try leaving fan on continuously.