R 3 Controls Valves Accessories Heat Pumps 4

R 3 Controls, Valves, Accessories & Heat Pumps #4 Heat Pump Operation © Refrigeration Training Services - R 3 Subject 4 Heat Pump Operation v 1. 2

The Heart of the Heat Pump Reversing valve: Determines indoor/outdoor coil function Usually energized in Cool position Four pipes: 1 Discharge inlet (always) 1 Suction outlet (always) 2 Switch from indoor to outdoor coils The following 2 slides show suction and discharge gas are switched © Refrigeration Training Services - R 3 Subject 4 Heat Pump Operation v 1. 2 2

Suction Gas (Always) To Outdoor Coil Reversing Valve: Reversing Valve- Cooling Mode Heating and Cooling Modes From Indoor Coil Discharge (Always) Compressor © Refrigeration Training Services - R 3 Subject 4 Heat Pump Operation v 1. 2 3

To Outdoor Coil Reversing Valve: Reversing Valve- Heating Mode Heating and Cooling Modes From Indoor Coil To Indoor Coil Suction Gas (Always) From Outdoor Coil Discharge (Always) Compressor © Refrigeration Training Services - R 3 Subject 4 Heat Pump Operation v 1. 2 4

Heat Pump in Cooling Mode TEV system • Discharge gas condenses in outdoor coil – Rejects heat from indoor coil • Liquid goes to indoor coil TEV • Indoor coil vaporizes liquid – Absorbs heat from space • Vapor returns to compressor © Refrigeration Training Services - R 3 Subject 4 Heat Pump Operation v 1. 2 5

Heat Pump w/ TEV - Cooling Cycle Coil ABSORBS heat from the space Indoor Coil Outdoor Coil REJECTS heat from the indoor coil Reversing Valve Compressor © Refrigeration Training Services - R 3 Subject 4 Heat Pump Operation v 1. 2 6

Heat Pump in Heating Mode TEV system • Discharge gas is directed to indoor coil – Uses suction line, in reversed direction • Indoor coil condenses gas to liquid • Liquid bypasses TEV through check valve • Liquid flows to outdoor coil – Uses liquid line, in reversed direction • Check valve forces liquid through outdoor TEV • Outdoor coil absorbs heat from outdoor air • Suction vapor is returned to compressor suction © Refrigeration Training Services - R 3 Subject 4 Heat Pump Operation v 1. 2 7

Heat Pump w/ TEV - Heating Cycle Indoor Coil Outdoor Coil Reversing Valve Compressor © Refrigeration Training Services - R 3 Subject 4 Heat Pump Operation v 1. 2 8

Heat Pump in Cooling Mode Piston metering device • Discharge gas condenses in outdoor coil – Rejects heat from indoor coil • Liquid goes to indoor coil – Piston moves out of the way in liquid line • Liquid goes through piston at indoor coil – Heat from space is absorbed in refrigerant • Vapor from indoor coil returns to compressor © Refrigeration Training Services - R 3 Subject 4 Heat Pump Operation v 1. 2 9

Heat Pump w/ Piston - Cooling Cycle Indoor Coil Outdoor Coil Reversing Valve Compressor © Refrigeration Training Services - R 3 Subject 4 Heat Pump Operation v 1. 2 10

Heat Pump in Heating Mode Piston metering device • Discharge gas is directed to indoor coil – Uses suction line, in reversed direction • Indoor coil condenses gas to liquid – Liquid pushes piston out of the way • Liquid flows to outdoor coil – Uses liquid line, in reversed direction • Liquid forced through piston metering device – Outdoor coil absorbs heat from outdoor air • Suction vapor is returned to compressor suction © Refrigeration Training Services - R 3 Subject 4 Heat Pump Operation v 1. 2 11

Heat Pump w/ Piston - Heating Cycle Indoor Coil Outdoor Coil Reversing Valve Compressor © Refrigeration Training Services - R 3 Subject 4 Heat Pump Operation v 1. 2 12

Heat Pump Defrost Cycle • Outdoor coil develops frosts in heating cycle – Operates 10 to 15 ° below outdoor ambient • Defrost by reversing to cooling mode: – Outdoor coil becomes a hot condenser – Outdoor fan shuts off – Indoor coil becomes an evaporator – Electric strip heaters warm air off evaporator There is more info on heat pump defrost circuits on the Instructor CD for HVACR Electricity & Controls © Refrigeration Training Services - R 3 Subject 4 Heat Pump Operation v 1. 2 13

© Refrigeration Training Services - R 3 Subject 4 Heat Pump Operation v 1. 2 14