Final answer:
Drainage should be provided for the defrost cycle when installing a heat pump outdoor unit to prevent water accumulation or damage.
Step-by-step explanation:
When installing the heat pump outdoor unit, care should be taken to provide for drainage during the defrost cycle. A heat pump is a device that moves thermal energy from a cold environment to a warmer one by using a working fluid such as a non-CFC refrigerant. In heating mode, the outdoor coils (the evaporator) facilitate heat transfer to the working fluid from the external cold air, causing it to turn into a gas.
When the heat pump operates in reverse during the cooling mode as an air conditioner, it will defrost and may produce water as the ice on the coils melts, necessitating proper drainage to avoid any water damage or accumulation around the unit.