McQuay IM 743 User Manual

OM 780-2 Page 69
Sequencing Constant Flow Pumps (if Pump Control Option = Sequencing, the following inputs are valid)
Name Description
Number of Sequenced
Pump Stages
If the Pump Control Option = Sequencing, this input defines the highest stage that the CSM will stage-up to in its
Pump Sequence Order table. Range = 1 to 9 stages. Default = 6 stages
Pump Stage Differential If the Pump Control Option = Sequencing, the CSM will not stage-down until the differential pressure is greater
than or equal to the Differential Pressure Setpoint plus this Pump Stage Differential. Range = 0 to 9 psi (0 to 62
kPa). Default = 2 psi (13 kPa)
Pump Stage-Up Delay
Time
If the Pump Control Option = Sequencing, the next stage-up cannot occur until after this period of time expires.
Range = 1 to 60 minutes. Default = 2 minutes
Pump Stage-Down Delay
Time
If the Pump Control Option = Sequencing, the next stage-down cannot occur until after this period of time expires.
Range = 1 to 60 minutes. Default = 5 minutes
Stage 1, Pump 1
Stage 1, Pump 2
Stage x, Pump y
These input values are used to set the pump order if the Pump Control Option = Sequencing. See the “Pump
Logic: Sequenced Pumps” section later in this document for further information.
The CSM can control a variety of chilled water distribution system equipment in several combinations. There are seven
basic configurations:
1. Constant-speed secondary pump, with optional pressure-controlled loop bypass valve
2. Constant-speed lead/standby secondary pump set, with optional pressure-controlled loop bypass valve
3. Constant-speed sequenced pumps (two to six), with optional pressure-controlled loop bypass valve
4. Variable-speed cooling load pump
5. Variable-speed lead/standby cooling load pump set
6. Multiple Variable-speed pumps (two to six)
7. Optional pressure-controlled loop bypass valve (primary-only system)
Typical, schematic representations of these configurations are shown in Configurations 1 through 6. Configurations 1
through 5 are primary-secondary (Decoupled) systems. Configuration 6 is a primary-only system.
The following sub-sections are organized according to the types of equipment that you may have in your system. You only
need to read the ones that apply to your application. For example, if your system is like configuration 4, you should look at
“Pump Logic: Single Pump” and “Pump Speed Control.” Or if your system is like configuration 3 with the optional bypass
valve, you should look at “Pump Logic: Sequenced Pumps” and “Loop Bypass Valve Control.”
Figure 30. Configuration 1: Constant-Speed Single Pump
DPT
Differential pressure transducer
P1
Cooling Loads
Optional pressure-controlled loop bypass
ChWR ChWS a0152

McQuay IM 743 Specifications

General

Brand	McQuay
Model	IM 743
Category	Controller
Language	English