[hvac1000]

One note. It has been proven that set back thermostats do not save energy when hooked to a heat pump under normal living conditions.

The reason is very simple in the fact that when the temperature is kicked back up by the thermostat usually both the heat pump and the electric resistance heat comes on. Running resistance heat is very expensive in most locations and should be avoided whenever possible. Some folks will say that if you use the new style thermostats that allow you to lock off the resistance heat and only allow the heat pump to run during recovery but the problem with that is most times the recover period with heat pump only is very long and most people just hit the emergency heat switch or cancel the set back once again using more energy than necessary by using resistance heat.

These tests were performed in a test chamber and also in a few selected homes and the results were always the same. All the major thermostat manufactures are aware of these results and if you talk to them directly will admit to these facts. Naturally they love to sell thermostats but with the GREEN movement playing an ever more important part in the HVAC business they have found the truth is always better than fiction.

This was just mentioned since you will probably be making a purchase of new equipment and many times contractors like to sell a expensive energy saving thermostat. This info will put your knowledge on a level playing field along with your future contractor in the thermostat selection department.

[DIYerGUY]

Check out figure 14 in the following document. It has a K terminal. http://customer.honeywell.com/techlit/pdf/60-0000s/60-1152.pdf