IOMM AGZB1 AGZ 010B through 034B 15
2. Start auxiliary equipment by turning on the following: time clock (if present), ambient
thermostat and/or remote on/off switch, chilled water pump.
3. If the controller calls for cooling, the unit will begin the start-up sequence.
4. After running the unit for a short time, check the oil level in the compressor (1/4 to 1/3
of the glass), rotation of fans, and flashing in refrigerant sight glass.
5. Verify superheat temperature is at the factory setting of 8 to 12 degrees F (4.4 to 6.7
degrees C).
6. After system performance has stabilized, complete the current AGZ Start-Up Form
(obtainable from the local McQuay sales office) to establish inception of warranty
benefits. Return the form to McQuay International through your sales representative.
Sequence of Operation
Start-Up
With the control circuit power on, 115V power is applied through the control circuit fuse F1
to the compressor crankcase heaters, the compressor motor protections and the primary of
the 24V control circuit transformer. The 24V transformer provides power to the
microprocessor controller.
When a remote time clock, manual switch, or the unit controller turns on the chilled water
pump, the flow switch closes and satisfies the flow requirement. If the chilled water
temperature is above the stage-on temperature, and all equipment protection devices are
closed, the unit will start. The controller will operate the unit in response to the leaving
chiller water temperature or reset signals that may be present.
Equipment Protection Alarms
The following conditions will shut down the unit and activate the alarm circuit:
• No evaporator water flow • Low evaporator pressure
• High condenser pressure • Motor protection system
• Phase voltage protection (Optional) • Outside ambient temperature
• Evaporator freeze protection • 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, ice, glycol, or test operation mode.
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 leaving water control is satisfied, it will stage off the lag compressor unloading the
unit. The second stage will de-energize the liquid line solenoid valve SV1 and shut off the
lead compressor. 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 56 for detailed explanation of compressor staging.
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