dual fuel heat pump

[Gary]

My thermostat has a setting for first stage differential and second stage differential Could someone explain what these 2 terms mean.

[Bob]

First stage is the heat pump. Second is the backup strip heaters, which are much less efficient. Differential is the difference between the turn on temp and the turn off temp.

Bob

[SQLit]

every stat has a range that it activates in. Your has 2 ranges. Assuming for a minute that you have a 2 stage gas furnance one stage would come on and start to heat. The stat and or the unit itself would expect to see the temp rise with in a period of time. If that does not happen then the second stage would kick in to bring the temp to the set point.

Differential is the dead band of stat. Set point of 70 F, dead band of 2 degress, 69-71F. Differential are settable to some extent depending on your application and equipment.