| CPC F24F 11/84 (2018.01) [F24F 5/001 (2013.01)] | 20 Claims |

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1. A heater system for heating a piece of equipment, the heater system comprising:
a reversing valve including:
a first refrigerant inlet,
a first refrigerant outlet,
a second refrigerant inlet, and
a second refrigerant outlet;
a refrigerant compressor including:
a third refrigerant outlet coupled to the first refrigerant inlet, and
a third refrigerant inlet coupled to the first refrigerant outlet;
a condenser including:
a fourth refrigerant inlet coupled to the second refrigerant outlet,
a fourth refrigerant outlet,
a coolant outlet coupled to the piece of equipment, and
a coolant inlet coupled to the piece of equipment;
an electric resistance heater coupled between the coolant outlet and the piece of equipment;
an evaporator including:
an evaporator inlet coupled to the fourth refrigerant outlet, and
an evaporator outlet coupled to the second refrigerant inlet; and
a controller for causing the reversing valve to operate between a first mode in which the piece of equipment utilizes a refrigerant, circulating in a first direction and heated via the evaporator, to maintain the piece of equipment within a desired temperature range, and a second mode in which the evaporator utilizes the refrigerant, circulating in a second direction opposite the first direction and heated via the piece of equipment, to defrost the evaporator, wherein the controller is configured to control the electric resistance heater to heat a coolant circulating between the condenser and the piece of equipment to maintain the piece of equipment within the desired temperature range in the second mode.
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