I have a 5000 sqft home with dual natural gas furnaces and AC Units. The main unit covers the basement and main level of the home. And the second unit is installed in the attic above the bedroom level (3rd level). The thermostat for the main unit is in the family room and the thermostat for the second unit is in the master bedroom.

My question is what is the optimum setting for these units to work most efficiently? Should they be set at the same temperature or is there some formula or ratio for this type of configuration? Any help or info would be greatly appreciated.

Thanks,

Moose

Optimum settings will be judged by the owner of the property and there comfort level. It is a personal choice.

Efficiency is determined by the equipment that is used.
I have three zones and they are all set different for different times of the day. This is determined by a computer program after imput feed back from the zones over a period of two weeks. All it does is save energy by lowering the temperature in the heat cycle to suit my families needs during a twenty four hour period. It also uses a outdoor reset thermostat on the boiler to allow more heat output as the temperature drops. It does the reverse on all three central A/C units in the summer.

If you do not use an area during sometimes of the day lower the temp to save energy. I would also recommend a ramp type stat. IE Honeywell with the adaptive intelligent recovery so the area will ramp up automatically before the desired usage time.