what is a single stage heat pump? vs a multi stage heat pump?

Question

i am trying to put in a new programable thermostat and i dont know which i have. it is a carrier heat pump that was put into the house in 1997.

Answer 1

We know that a single stage heat pump is a heat exchanger and a fan. That's it. Here's something from the Dept. of Energy describing exactly what a multi-stage heat pump is:

For a material processing operation having at least one stage requiring heating and at least one stage requiring cooling, heating is provided by a first heat pump and cooling is provided by a second heat pump, with two storage tanks of different temperatures being provided, the second tank serving as a heat sink for the condensing section of the second heat pump, and serving as a heat source for the evaporator section of the first heat pump, the first tank providing a cooler fluid for the condenser section of the second heat pump, and receiving a cooled fluid from the evaporator section of the first heat pump.