Heatcraft Refrigeration Products none Head Pressure Setpoint, Minimum Output, Throttling range

Head Pressure Setpoint

The head pressure setpoint potentiometer is adjustable from 90-250 psig. .A typical setpoints are from 170-200 psig. . Note: Very low setpoints may cause the fan motors to run full speed continually if the condenser is not properly sized. . The fans will turn off if the system pressure falls below the desired setpoint..

Minimum Output

The minimum output potentiometer controls the minimum signal sent to the motor. .It is adjustable from 0-60%. .If this is adjusted to 60%, the motors will not start running until 6V is applied to the motor. .The motor will start running at 60% of full speed. .To maximize sound reduction and energy savings and to provide the most stable control, it is recommended this setting be left at 0%..

Throttling range

The throttling range potentiometer controls how far the system pressure must deviate from the control setpoint to generate a 100% output signal from the control. .It is adjustable from 10-100 psig. .The throttling range determines how quickly the motor will reach full speed when detecting a change in head pressure. .For example, if the setpoint is 200 psig and the throttling range is 50 psig, when the system pressure is below 200 psig, the fans will be off. . When the system pressure reaches 250 psig, the fans will be at full speed (see Chart 1 below).. To make the fans ramp more slowly the throttling range should be increased (see Chart 2 below).. To maximize sound reduction and energy savings and to provide the most stable control, it is recommended this setting be left at 100 psig..

Integration constant

The integration constant switch provides ability to change controller from a proportional only control to a proportional plus integral control..To provide the most responsive system to maintain a stable head pressure, it is recommended this setting be left on “fast..”

Reverse acting or direct acting mode of operation

The reverse acting/direct acting jumper is used to ensure the controller responds correctly to maintain desired head pressure. .In Direct Acting (DA) mode, the motor speed increases as the pressure rises above desired setpoint. .For proper condenser operation, this jumper MUST be in Direct Acting (DA) mode. .Failure to ensure J1 jumper is in direct acting mode will cause the system to trip on high head pressure..

See Diagram #4 for typical proportional pressure control wiring..

Motor RPM Motor RPM

Chart 1. .Ramp characteristics with 200 psig setpoint and 50 psig throttling range

Chart 2. .Ramp characteristics with 200 psig setpoint and 100 psig throttling range

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