switch from heat to a/c on thermostat

Hello, Due to sudden temp changes, sometimes there is a need to switch from heat to A/C.
I was wondering if this is harmful to the heating/cooling units.
The unit is in the attic and the heat is gas-powered. The same unit is used for A/C.
The heater/AC is about 6 years old.
Thanks!
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that is what the units are made for. I would not switch from heat directly to cool when the unit running or visa versa. As long as the unit is not running there should be no problem.
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Some electronic thermostats will automatically switch between heating and cooling without using a switch. I had an Emerson stat that did this. Sorry, I don't remember the model.
One thing you want to avoid is short-cycling your A/C Compressor. This means turning it off and then turning it on again right away. The high pressure differential causes extra stress on the compressor when starting and may burn out, trip breakers, fuses, etc.
Some thermostats have built-in short cycle prevention. There is a time delay of 2 minutes or so while the difference in pressure between the high side and the low side is allowed to blead off. Cheaper thermostats do not have short cycle protection.
Beachcomber
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