Last December I had my 16-yr. old single-stage HydroHeat geothermal heatpump replaced with a single-stage Water Furnace Envision. Both units are about 4.5 ton capacity. The old HH had a 3-speed squirrel cage motor that I had set on the middle speed. The new WF has an 12-speed ECM motor and a desuperheater.

My house is 1,688 sq. ft. on the main floor with vaulted ceilings reaching 15 ft. high. The lower level has about 1,600 finished sq. ft. for a total of just over 3,200 sq. ft. All ducts and returns on the main level are at the baseboard.

The Hydro Heat (HH) had no problem heating or cooling. The Water Furnace (WF) heats fine but has serious problems cooling the main floor. With outside air temp over 85F and the thermostat set at 70F, the main floor at thermostat level will cool to 74F. The temp at the floor is 66F. Eight degrees difference from head to toe. Needless to say, this is not comfortable.

I do not recall the cfm rating on the HH. The max cfm rating on the WF with ECM is 1,550. I notice a definite difference between the two in airflow with the WF blowing a very light breeze through the ducts. The HH blew much harder.

The air on the main floor is very stratified and uncomfortable. My installer seems to be guessing at this point, saying that I need high returns, and is blaming the house. I understand his logic, but I also understand the old HH had no trouble cooling the place quite comfortably and a WF of the same size should not have any trouble either.

Any advice would be greatly appreciated. I bought what many consider to be one of the finest heatpumps available and probably spent way too much money. This dilemma is really frustrating.