Are they refusing to come out and check out the system? Wow, that is scary. I'm in the market for a new system soon and hope I choose a contractor that is better than that. Is the air coming out of the vents cold, not just "cool"? Any way you can measure the air from the vents?

measure temps at evap coil before and after. see whats going on.

Did they check the duct work under the house?
BIG culprit.
Is your attic insulated real good?

The company that installed it did come back out, but they seemed to think that opening the vents would fix the problem. They seemed satisfied with the temps coming out of the registers. They said we might need to take one vent out of a room that gets real cool and put an extra vent in another area. I just don't understand why the ductwork and vents were never a problem before this new a/c. The guy suggested that the R410A units are less forgiving about bad layouts or ductwork. Anybody have any idea why it would be any different? We will probably have the insulation checked, but it wasn't a problem before the new a/c. Thank you all very much for responding. I appreciate the help in solving this problem.

You didn't mention that you have some rooms that are getting real cool and others that are warm. That suggests that maybe the CFM (volume of air) of the new system is not the same as the old and is not getting evenly distributed within the branches of the ductwork.

As for the R410A being not as forgiving, I would think that 3 tons of A/C is three tons of A/C no matter what the refrigerant.

brand/model of old and new system? Was a ManualJ calculation done to confirm 3 tons?

Models that say they are a nominal 3 tons may actually be something different depending on the coil/blower combination.

Here are the model #s:
A/C Before- Goodman CK36-1A, A/C After- Carrier 24ABB336A340. Although, for some reason when I put my serial number in Carrier's warranty website, it said the model number was 24ABB336A003 (don't know if that's a problem).

Coil Model Before- unknown, Coil After - Carrier CNPVP3617ALA.

I don't know if they did a calculation to determine the size or if they just went with 3 tons because that's what we were replacing, and it had worked fine.

Is there an inexpensive tool to measure the air flow out of each register or do just HVAC people have those?

We know we had dampers in at least one duct back when we first moved in. Do those ever get messed up in the process of replacing the coil?

Seems to me that your contractor should be verifying that the airflow at the coil is what it should be for a three ton system. Maybe one of the HVAC experts can chime in here, but the coil itself is an obstruction in the airflow and with the high efficiency coils with all the folds and the same blower and motor in your furnace, the airflow may not be what it was with the simpler design old R-22 coil.

Edit: One of the things I learned from the advice on this forum is that it is always risky to replace just a portion of a system.

This post was edited by Dovetonsils on Sun, Jul 13, 14 at 18:41