Should a heat pump cool below 59 degrees?

A heat pump generally has a max temperature change of 20 degrees F. If air entering the return duct is 90, it will not be cooler than 70 on the discharge side, Below 60, it is working against the insulation and air infiltration into the house. It is an air conditioner, not a deep freeze. Remember that a heat pump either dumps heat outside to cool a house, or picks up heat from outside to heat the house. If it is 100 degrees outside, it is hard to dump heat. Below 35, it is hard to pick up heat. At an outside temp of 59 degrees, it should work for either- but nobody needs cooling when it is 59 degrees outside. Open a window, already!.