Unit installation

64 IOMM ACZ/AGZ
Remote 4-20 milliamp signals
Signals for leaving water reset or demand limit are provided by the installing contractor and
connected to the terminal block as indicated by the unit wiring diagram. See Field Wiring diagram
for details.
Interlock wiring
All interlock wiring to field devices (such as flow switches and pump starters) is provided by the
installing contractor. See unit wiring diagrams and field wiring diagram.
Unit set points and calibration
The control software is installed and tested by the factory before shipping. Calibration of the
controller is not necessary. All control and safety set points must be checked by the installing
contractor and adjusted as necessary before starting the unit. Controllers for McQuay chillers have
default set points. Refer to the menu items listed below.
• Control mode
• Leaving water temperature
• Head pressure settings
• Compressor staging
• Soft loading
• Holiday dates
• Internal scheduling
• Alarm functions
The default settings are suitable for most installations. The control mode is factory set for “Manual
Unit Off”. Check and set the control and safety settings for the application before starting the unit.
For more information on menu items, see the menu description section.
Modem kit
An optional modem kit allowing remote monitoring of the chiller from an off-site PC running
McQuay Monitor software is available from your local McQuay International sales representative.
The modem kit comes complete with modem, mounting bracket, wiring harness, and installation
instructions. The modem kit can be field installed or as an option at the factory. Modem wiring is
shown on the field wiring diagram.
Lead-Lag
A feature on all McQuay AGZ air-cooled chillers is a system for alternating the sequence in which
the compressors start to balance the number of starts and run hours. Lead-Lag of the refrigerant
circuits is accomplished automatically through the MicroTech Controller. When in the auto mode
the circuit with the fewest number of starts will be started first. If all circuits are operating and a
stage down in the number of operating compressors is required, the circuit with the most operating
hours will cycle off first. The operator may override the MicroTech controller, and manually select
the lead circuit as circuit #1, #2, #3 or circuit #4.