I have a problem. I just installed a new 12 SEER Grandair 3 ton unit in my house. I have a zone system which has a thermostat in the main floor, and another thermostat in the upstairs bonus room. I have the main level thermostat set on cool at 73 degrees. I have the upstairs thermostat set at 76 degrees. The system freezes up completely. I know it is an air flow problem. I suggested to take out the doors from the zone system and have only one thermostat control the whole house to keep the unit from freezing up. Do you have a better suggestion?? ---HELP---

You are sure it is an airflow problem? How. What about a charge problem?

It's not a charge problem because I put the cages and the charge is good...

I am saying airflow problem because there are only 4 air vents upstairs on at one time. On the main floor there is 10 air vents...

Was there a bypass damper installed in the basement? Or is your ductwork sized big enough to run one floor at a time?

How many returns are on each floor?

There are 10 returns on the main floor, and 4 on the second floor.

Yes there is a damper.

So you have 14 returns and 14 supplys? What size is your duct downstairs? And do you have a bypass damper between the supply and return?

The Duct for the downstairs is larger than the duct that feeds the upstairs. Do not have the exact measurement. No there is no bypass between the 2 ducts under the house.