Don Young wrote:
"Harlan Messinger" wrote in message
...
My house is on three floors, it has central air conditioning, the
thermostat is on the middle level, and there's an exhaust fan on its own
thermostat in the attic. When the temperature is comfortable on the middle
floor, it's too warm on the top level. It's a bit cooler on the ground
floor.

What's the most effective, assuming any of them is effective, of the
following approaches?

1. Partly close the incoming air vents on the middle floor and possibly
the ground floor. The theory: a relatively larger portion of cooled air
will go to the top floor.

2. Hang a ceiling fan in the stairway between the second and third floors
to push the air upwards.

3. Hang a ceiling fan in the stairway between the second and third floors
to push the air downwards.
This common situation can be improved by running the evaporator fan
continuously. The fan speed for best balance between cost and effectiveness
can be determined experimentally. Reducing the heat gain in the upper floors
also helps.

Do you mean, the fan switch on the thermostat? I always have that on On,
rather than Auto. But there isn't a speed adjustment.

What do you mean by "reducing the heat gain"?