Appendix A: Hardwired Chiller Control - McQuay MicroTech II Installation Manual

Appendix A: Hardwired Chiller Control

This appendix provides information about using the CSM to control chillers via hardwired binary and analog inputs and
outputs. This option should be used when a serial communication option is not available since control, monitoring, and
alarm indication is reduced. Hardwired chillers have control features wired to a remote I/O module mounted near the
chiller's unit controller. The hardwired chiller's remote I/O module communicates with the CSM via a L
network. The CSM controls the chiller using the following outputs on the remote I/O module:
1. Remote Auto/Stop (Relay Output)
2. Evaporator Pump Enable – if the chiller is not controlling its own pumps (Relay Output)
3. Condenser Pump Enable – if the chiller is water cooled and not controlling its own pumps (Relay Output)
4. Chiller Leaving Water Temperature Setpoint Reset (Analog Output)
5. Capacity Limit (Analog Output)
The CSM receives the following information through the remote I/O module's inputs:
1. Proof of Evaporator Water Flow (Digital Input)
2. Proof of Condenser Water Flow - on water cooled chillers (Digital Input)
3. Chiller Alarm Output (Digital Input)
4. Second Chiller Alarm Output – if the unit has multiple compressors, the chiller provides two alarm outputs
(Digital Input)
5. Compressor Percent Rated Load Amps - % RLA (Analog Input)
6. Optional Chiller Evaporator Leaving Water Temperature (Analog Input)
7. Optional Chiller Condenser Leaving Water Temperature (Analog Input)
Wiring of these points to the remote I/O module is shown in Figure 30.
IM 781-2
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