Saturday, October 3, 2015

Refrigeration System Sequence of Operation


Power is supplied to Timer Motor

Timer Motor controls time for Cooling and Defrost cycles

Room Thermostat Closes when the temperature rises above setpoint

Control Board will activate the Refrigeration/Cooling Mode

Timer Motor is on Refrigeration/Cooling Mode

Defrost Heater is Off

Defrost Limit Switch is Off

Defrost Termination Solenoid is Off

Defrost Termination Thermostat/Fan Delay Switch is On

Evaporator Fan Motor is On

Liquid Line Solenoid is energized

Liquid Line Solenoid Valve Opens to allow liquid refrigerant to Evaporator

Low Pressure Control/Switch is Closed

High Pressure Control/Switch is Closed

Overload Protection is Closed

Compressor Contactor Coil is Energized

Compressor Runs

Condenser Fan Motor Runs

When Desired Room Temperature is reached

Room Thermostat Opens

Liquid Line Solenoid is De-energized

Liquid Line Solenoid Valve Closes

Compressor continues to run to allow Pump Down of refrigerant

Low Pressure Control/Switch will Open

Compressor Contactor Coil will De-energized

Compressor will turn Off

Condenser Fan Motor will turn Off

When defrost time is reached by the Timer Motor

Defrost Mode/Cycle begins



Compressor Pump Down process

Timer Motor will be on Defrost Mode/Cycle

Defrost Heater is On

Defrost Limit Switch is On

Defrost Termination Solenoid is On

Defrost Termination/Fan Delay Switch is Off

Evaporator Fan Motor is Off

When defrost time is completed and Evaporator warms up

Defrost Termination Thermostat Closes

Low Pressure Control Closes

Compressor starts

Condenser Fan Motor Starts

Refrigeration Cycle Starts

When Evaporator coil temperature cools down

Fan Delay Switch will Close

Evaporator Fan Motor will turn On

Refrigeration cycle continues until the next Defrost Cycle is set by Timer Motor

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