I looked and searched for information to help me explain how a heat pump works. One source I went to was Carrier's web site, they invented air conditioning after all. Under heat pumps it says, "For more on heat pumps go to E-Hows web site." Carrier was right. It is the best and most complete information on and about heat pumps I have seen.
What is a Heat Pump? How Does It Work? What Climates Does It Work Best In? Can I Use It If I Have Gas? What About SEER?
All those things I planned to answer for you... Link below:
Pictures courstey of Google Images.