I have a heat pump that is part of a dual fuel system. It shuts off and then a furnace kicks on. Right now the Heat pump shuts off when the tempature falls below 45 degrees. Every thing I've read says the system is capable to down around freezing with no issues. How can I lower the heat pump set point? Where would I find it on the unit itself? I had one of the covers off but there is nothing there indicating a set point. Any help?