McQuay IM 743 User Manual

Page 128 OM 780-2
Hardwired Chiller - Load Limiting Control
The CSM can limit the loading of each chiller in the system from 100% to 40% by sending it a capacity limit. The CSM
generates the load limit for each chiller based on a demand limiting, soft load, or load-balancing function (see the Load
Limiting Control section for details). The capacity limit is sent to a hardwired chiller via analog output (AO 2) on that
chiller’s hardwire remote I/O module.
The output signal from the CSM to the chiller is shown in Figure 53.
Figure 53. External Demand Limiting Function Signal
40
60
80
100
CSM Capacity Limit (% Load)
0246 108
04812 2016
Hardwired Signal to Chiller
0–10 Vdc:
0–20 mA:
The chiller must be configured to have a demand limiting range corresponding to the CSM’s signal. Its maximum amps (at
2 Vdc or 4 mA) must be set to allow full chiller capacity and its minimum amps (at 10 Vdc or 20 mA) must be set to
approximately 40% of full load. The chiller must also be configured to enable demand limiting from a 2-10 Vdc (or 4-20
mA) source.
Hardwired Chiller - Chilled Water Temperature Control
In a system of multiple hardwired chillers, each individual chiller maintains its leaving evaporator water temperature based
on the individual chiller setpoint. Each chiller’s setpoint should be set to the same value. The CSM generates a system
reset based on a number of different functions (see Chilled Water Temperature Control on page 49.) The CSM’s system
reset is sent to a hardwired chiller via an analog output (AO 1) on that chiller’s hardwire remote I/O module. The output
signal from the CSM to the chiller is shown in Figure 54 and Figure 55.

McQuay IM 743 Specifications

General

Brand	McQuay
Model	IM 743
Category	Controller
Language	English