I have recently purchased a house that has been vacant for the past 18 months. During the inspection, it was noted that the heat pump (Heil) and air handler (Amana) were mismatched. I'm told that pressures and temps are good and air flow through the handler seems OK by the folks who have come out to provide estimates.

The past week has been exceptionally warm for this time of year, and as a result the air conditioner has been able to maintain (but not drop) existing house temperature until the afternoon, at which point it can no longer keep up and starts to increase as the day gets long. I have received estimates and it seems no one is in total agreement on what the root issue is so the solutions vary. I'm optimistic that folks on this board can provide some solid guidance.

Details:

- 2200SF split layout, ranch-style house in central Florida (built late 80s)

- 4-ton HP and air handler, both appear to be 2001 units

- Several sliding glass doors and windows, with primarily east/west exposure.

- Vaulted ceilings in about half the house.

- Two air returns: 20x25 (centrally located) and 12x12 (master bedroom/bath)

My conflicting estimates come from both a sizing and ductwork perspective. Two estimates say five-ton units are the proper size, whereas the other two say four tons will suffice. The two four-ton estimates indicate that new ductwork is needed, as it is not properly sized to handle the airflow for the house (e.g., there is a five-inch vent in the kitchen, and a nine-inch duct running to cool one whole side of the house). Additionally, one from each camp suggests another return should be installed; a 12x12 return for about 1/3 of the SF of this house is too small.

It would seem that if ductwork is to blame, then replacing it would yield a more comfortable house even with the existing, "working" 4-ton system in place. The two estimates that suggested ductwork also spent the time to do some load calculations. However, given the higher ceilings, sliding glass doors, etc., perhaps a larger system is better.

From reading these boards, I know that a system too large is actually detrimental to cooling *and* more costly to run...and living in Florida the A/C is going to run the good majority of the year.

Feedback and commentary would be greatly appreciated.