Registers are not blowing air

Macgyver

I'm having a fairly serious problem with my HVAC. I've recently bought a condo that was rehabbed. The HVAC inside the unit was new, so I never questioned its capability during the entire buying process.

I have ceiling registers, and I can only feel a trickle of slightly warm air coming through. The heating unit I have is one that is definitely blowing air into the ducts(I can put my hand up next to the large exit duct and feel the air moving), and I can feel the cold air return to say that it is definately sucking air (though I can't gauge how much). In order to maintain an even heat, I have to keep the blower fan running constantly, and it takes a long time and the heater cycles on and off very often.

I have checked, and replaced, the filter with a HEPA rated one. What the heck is wrong with this HVAC unit?

Christopher

Macgyver,

Very few HVAC installations work properly with any filter other than the cheap spun fiber glass types.

To check airflow, remove the filter and run system - you should get high air-flow with no filter. Install new cheap spun fiber glass filter, airflow should be just about as good.

Report back...

...Christopher

Macgyver

Chris,

Thanks for the info. I will attempt your suggestion with the cheap filter, but I don't think it's going to make a difference. It wasn't blowing well before I installed the new filter. I'll post tonight and let you know.

Macgyver

Chris,

I gave it a shot, and pulled the filter. The vents are now producing a lot more air then they were before, though it's still not what I would consider ideal(an old game of mine when I was little was to place a sheet over the ones in my parents house and build a tent. Maybe that's too optimistic).

Would trying a different cold air return grate help any? The one I have appears to be small. I can see some 2x4s behind it too, would cleaning those blocks out help? What are some of the considerations?

Mike

Christopher

Mike,
You have confirmed my suspicion, that like most installations, your set-up can only use a non-HEPA filter.
These may be structural so removing these may not be an option.

Is your system now running normal cycles?

What type of heat do you have -
Gas?
Electric heat strip in air conditioner? How many KW (watts)?
Heat Pump?

What is the supply grill temp when the heat is on?

Does your filter go in the unit or the return air grill?

What is the filter size?

...Christopher

Macgyver

It's an option, the condo is a rehab where the entirety of the wood is only used to do the interior wall seperations. The structural portions of the condo are at the walls and the core, which are constructed of reinforced concrete beams. The area I'm talking about has about 3.5 inches of drywall blocking the top part of the cold air return as well as 2x4s in the way as well.

Natural Gas. And LOUD. Blower off, SSSSSSS, Click Click, Bang, Whoosh(ignition), blower on.

Don't know, and I'm out of town on business so I can't check.
Filter is underneath the unit, unit is propped up on a slightly sealed 2x4 box. I'd say it's part of the unit. The filter size is something like 12x24 or 14x24... I don't remember off the top of my head.

redline

Did you check to see if any of the heat ducts have seperated and are losing the heated air into the attic or other space?