Control Sequence of Operation

Now that the compressor motor (4M1) is running in the ‘‘Delta’’ configuration, the inlet guide vanes will modulate, opening and closing to the chiller load variation by operation of the stepper vane motor actuator (4M2) 4M4 (extended capacity) to satisfy chilled water setpoint. The chiller continues to run in its appropriate mode of operation: Normal, Softload, Limit Mode, etcetera. As explained in the General Information section.

If the chilled water temperature drops below the chilled water set point by an amount set as the ‘‘differential to stop’’ setpoint, a normal chiller stop sequence is initiated as follows: (Refer to Figure 10.)

1.The inlet guide vanes are driven closed for 50 seconds.

2.After the 50 seconds has elapsed, the stop relay (2A1-J10) and the condenser water pump relays (1A5- J2) open to turn off. The oil and refrigerant pump motor (4B3) will continue to run for 3 minutes post lube while the compressor coasts to a stop. The chilled water pump will continue to run while the Main processor module (1A22) monitors leaving chilled water temperature preparing for the next compressor motor start based on the ‘‘differential to start’’ setpoint.

If the STOP key is pressed on the operator interface, the chiller will

follow the same stop sequence as above except the chilled water pump relay (1A5-J2) will also open and stop the chilled water pump after the chilled water pump delay timer has timed out after compressor shut down.

If the “Immediate Stop” is initiated, a panic stop occurs which follows the same stop sequence as pressing the STOP key once except the inlet guide vanes are not sequence closed and the compressor motor is immediately turned off.

CDHF-SVU01C-EN

69

Page 69
Image 69
American Standard CH530 manual Control Sequence of Operation