When running AC, Heat turns on once thermostat reaches desired temperature

Question

I just recently installed a new wifi thermostat for my system. I went from a Trane to a Honeywell. I followed the instructions and put the wires in the right terminals (i believe)

Everything is running great... except when the thermostat reaches the desired temperture.

for example, room temp is 83 degrees. I set it to 77. It cools the house down to 78. Once it reaches 77, it automatically kicks on the heat until it jumps up to 78, and kicks on the AC. What gives? Any help would be greatly appreciated!

Answer 1

Check your set points. You'll want to have a degree or two between the heating and cooling set points. For example, if your cooling set point is 76°F, you'll want to keep the heating set point at or below ~74°F. Check the documentation for your unit, to determine the recommended buffer value.

Also note that some units allow you to program the swing setting, which determines how far off from the set point before the unit signals for heat/cool. For example, if you have a heating set point of 68°F, with a swing setting of 1°. The heating system will be signaled ON when the temperature is 67°F, and signaled OFF at 69°F.

In the above example if you had the cooling set point set to 68°F too, you'd end up fighting for control. Heat would bring it up to 69°F, then cooling would kick on and bring it down to 67°F, then heating would kick on and bring it up to 69°F...

I'd try to keep a buffer of at least 1°F. So if the swing is 1°F, you'd set heating to 68°F and cooling to 70°F. Some documentation recommends only a single degree (heat=68°F, cool=69°F), but I'd recommend keeping at least one degree between the set points.