Heat pumps freeze in cold weather, especially if you live in an area with cold, snowy winters. Light frost on the pump is normal, but if the system becomes encased in ice, there may be something wrong with your heat pump's defrost setting. If the unit is full of ice, you need to fix these settings or hire a professional. You must thaw the pump immediately to prevent the pipes from bursting.
Turn up the heat in your home. This allows heat to enter the area where the pipes are frozen, helping thaw them.
Turn on affected faucets. Open closet and cabinet doors to allow heat to enter areas with frozen pipes. In unheated areas, use a space heater. These measures will prevent the hot water supply from freezing.
Blow hot air onto the frozen pipes and heat pump using a hair dryer. Aim the dryer at the pipes. Wait for the ice to melt.
Call a plumber if your pipes are copper, brass or galvanized steel. Make sure the plumber uses an electric pipe-thawing machine -- not a torch -- on the pipes.