Unit installation

IOMM ACZ/AGZ-3 ACZ / AGZ-BM 21
ACZ Compressor Staging
Temperature control for the evaporator is provided by the installer through a field supplied and
wired temperature controller. The field supplied staging signals are field wired to the Microtech II
controller that correspondingly activates and deactivates the scroll compressors. The field supplied
temperature controller is required to close normally-open 24 volt contacts on a demand for cooling.
These closure signals are field wired to the terminal strip (TB3) in the condensing unit. Refer to the
field wiring diagram (page 49) for details. The following control staging is required:
Condensing Unit Model
Number of
Capacity Steps
Number of Required
Contact Closure Signals
ACZ-030B through 110B 4 4
ACZ-120B through 155B 6 6
Remote Evaporator Refrigerant Piping
Figure 20, AGZ-BM, Remote Evaporator Piping Schematic
Proper refrigerant piping can make the difference between a reliable system and an inefficient,
problematic system. The primary concerns related to piping are refrigerant pressure drop, a solid
liquid feed to the expansion valves, continuous oil return and properly sized refrigerant specialties.
The recommended source for refrigerant piping techniques and sizing is the ASHRAE 2002
Refrigeration Handbook, chapter 2.
Refrigerant specialties including the expansion valves, solenoid valves, filter-drier and sight glasses
for use with the AGZ-BM remote evaporator models are supplied by McQuay but require field
installation. No piping components are furnished on the ACZ condensing units. The remaining
components including fittings and Schrader valves are provided and piped by the installer. The hot
gas bypass valve with solenoid valve option can be provided as a field-installed or factory installed
option.