Page 26 / IM 778
High
Normal
Low
Normal
Low
Normal
Charge
Undercharge System
Low
Low
Low
High
Low
Low
Low
Low Pressure
(Possible Leak)
Overcharge System
High
High
High
Normal
High
Normal
High Pressure
Low Air Flow Heating
High
High
High
Low
High
Low
High Pressure
Low Air Flow Cooling
Low
Low
Low
High
High
Low
Low Temp
Low Water Flow Heating
Low
Low
High
Low
High
Low Temp
Low Water Flow Cooling
High
High
High
High
Low
Low
High
High Pressure
High Air Flow Heating
Low
Low
Low
Low
High
Low
Low
Low Temp
High Air Flow Cooling
Low
High
Normal
High
Low
Low
Normal
High Pressure
High Water Flow Heating Normal
Low
Normal
High
Normal
Normal
Low
High Pressure
High Water Flow Cooling
Low
Low
Low
Low
High
Normal
Low
Low Temp
TXV Restricted
High
Low
High
High
Low
Low
Normal
Low
Low
Normal
Cooling Mode
Return Air
Reversing Valve
Conditioned Air
(Cooling)
Thermal
Expansion Valve
Co-Axial Heat
Exchanger
Blower
Coil –
Air to
Refrigerant
Heat
Exchanger
Water In
Water Out
Sensing
Bulb
and
Capillary
Tube
Compressor
Air
Water
Safety
Head
Suction
Compressor
Super
Temp
(loops) Temp
Lock
Symptom
Pressure Pressure
Amp Draw
Heat
Subcooling Differential Differential
Out
Heating Mode
Return Air
Thermal
Expansion Valve
Co-Axial Heat
Exchanger
Reversing Valve
Conditioned Air
(Heating)
Blower
Water In
Water Out
Sensing
Bulb
and
Capillary
Tube
Compressor
Coil –
Air to
Refrigerant
Heat
Exchanger
Normal
Low
Troubleshooting Refrigeration Circuit
Cooling Refrigeration Cycle
When the wall thermostat is calling for COOLING, the
reversing valve directs the flow of the refrigerant, a hot gas,
leaving the compressor, to the water-to-refrigerant heat
exchanger. Here the heat is removed by the water and the
hot gas condenses to become a liquid. The liquid then
flows through a thermal expansion metering system to the
air-to-refrigerant heat exchanger coil. The liquid then evap-
orates becoming a gas, at the same time absorbing heat
and cooling the air passing over the surfaces of the coil.
The refrigerant then flows as a low pressure gas through
the reversing valve and back to the suction side of the
compressor to complete the cycle.
Heating Refrigeration Cycle
When the wall thermostat is calling for HEATING, the
reversing valve directs the flow of the refrigerant, a hot gas,
leaving the compressor, to the air-to-refrigerant heat
exchanger coil. Here the heat is removed by the air passing
over the surfaces of the coil and the hot gas condenses to
become a liquid. The liquid then flows through a capillary
thermal expansion metering system to the water-to-refriger-
ant heat exchanger. The liquid then evaporates becoming a
gas, at the same time absorbing heat and cooling the water.
The refrigerant then flows as a low pressure gas through the
reversing valve and back to the suction side of the com-
pressor to complete the cycle.
