Thermostat to controll heat and ac simultaneously?

Old 12-18-07, 12:31 PM
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Thermostat to controll heat and ac simultaneously?

I'm about to buying a new thermostat to control the humifier and this got me thinking even bigger hassle.

I live in the midwest and when the weather changes from summer to fall/winter, the mornings are cold and evevings are hot. So I have to turn the AC on during the day and switch to heat before I go to sleep. Is there a thermostat that will kick heat or ac on depending on the temperature?
I can leave without the built-in HUM but would love heat/ac simultaneous control.

Old 12-18-07, 01:34 PM
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Look for stat that has auto switch over or auto change over.
Old 12-18-07, 03:33 PM
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They come in both mechanical and digital varieties.

The mechanical one will have dual levers that stick out of the top. As you slide over the one lever, the other one automatically slides over also, so that the system is foolproof, so that you do not get simultaneous heat and a/c, or so it doesn't alternately go back and forth cooling - then heating, then cooling what you just heated, etc.

The digital one can be set to: Heat, a/c, or auto (and probably fan only, also). In auto mode, this will do just what you want. You also can program in the temperature differential you want between the heat and a/c settings, to reduce the risk of alternating heating, then cooling like mentioned above.

Under certain situations , if you have the settings for heat and cool too close together, (0 or 1 degree differential), outside factors can cause this unwanted cycling to occur. In an office building I maintained, every room had it's own control. Well, I found this one guy liked his room temp like Mr. Freeze in his office, and the cool got out his door, went around the corner and hit the auto thermostat in the other room and caused that persons HEAT to come on!! Sunlight infiltration, using a fireplace, cooking by the stat, etc., are things you will have to be aware of when setting up the stat in your situation to make sure this alternating does not occur. Under normal circumstances it won't, especially if you have say a 3 degree dif.: Say 75 for a/c and 72 for heat.

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