Unit installation

IOMM ACZ1-2 ACZ 010A through 039A 15
Equipment Protection Alarms
The following conditions will shut down the unit and activate the alarm circuit:
• No water or air flow • Low evaporator pressure
• High condenser pressure • Motor protection system
• Phase voltage protection (Optional) • Outside ambient temperature
• Sensor failures
The following alarms will limit unit operation:
• Condenser pressure stage down, unloads unit at high discharge pressures
• Low ambient lockout, shuts off unit at low ambient temperatures
• Low evaporator pressure hold, holds stage #1 until pressure rises
• Low evaporator pressure unload, shuts off stage #2
Unit Enable Selection
Enables unit operation from local keypad, digital input, or Building Automation System.
Unit Mode Selection
Selects standard cooling or test operation mode. (Test is for service personnel only.)
Condenser Fan Control
Control of condenser fans is provided by the MicroTech II controller. The control steps
condenser fans based on discharge pressure.
Shutdown
As the Stage #2 external staging thermostat is satisfied, it will stage off the lag compressor
unloading the unit. The Stage #1 will de-energize the liquid line solenoid valve SV1 and
the lead compressor will pump down the unit and shut off on Low Suction Pressure at 40
psig. If the low pressure cutoff point cannot be reached in 120 seconds, the compressor
will time off. The compressor crankcase heaters will energize when the compressors shut
off, keeping the small amount of refrigerant in the plate heat exchanger from migrating to
the compressor. See page Error! Bookmark not defined. for detailed explanation of
compressor staging.