What is the definition of a multi split heat pump? A multi split heat pump is a type of air-source heat pump, typically used for heating and cooling multiple rooms or areas at once. It works by taking heat from the surrounding air and transferring it to the desired indoor environment. The multi split heat pump is made up of multiple, wall-mounted indoor units connected to a single outdoor unit. Each indoor unit is split into two parts; an evaporator and a condenser. The evaporator absorbs heat from the outside air and transfers it to the condenser. The condenser then releases the heat into the desired room or area. The heat pumps may also be used to cool the desired environment. In this case, the evaporator absorbs the heat from the indoor environment and the condenser releases the heat to the outside air. Multi split heat pumps are more efficient than individual air conditioners, as they require only one outdoor unit, making them easier to install and maintain.