Fan Speed Control

Fan speed controller or low ambient fan controller is a control that is used to control the fan speed of the air-cooled condenser in a heat pump direct expansion system. Heat pump is used in temperate countries and can be used to operate in cooling or heating mode. When used as a heating mode in winter, the indoor coil acts as a condenser and outdoor coil as evaporator.

When the unit is set to cooling mode in summer, the indoor coil will operate as an evaporator and the outdoor coil as condenser. This is accomplished by the use of a 4-way-valve that reverses the flow of the refrigerant in the system. In the United States, usually when the reversing valve is ON, the system will operate in cooling mode and when it is OFF, in heating mode.