Product manual

68 IOMM ACR/AGR-1
Manual Operation
Manual operating modes are available to simplify setup and troubleshooting of the unit. Any of the
following manual modes may be selected from the Control Mode Menu.
Note: These manual settings are intended to aid in troubleshooting and should not be
considered to be normal operating modes. The equipment should not be left unattended
during manual operation as the automatic staging controls are disabled. The chiller will
remain in the manual mode until Automatic operation is selected or a problem alarm occurs
which will change back to the “Automatic mode”.
• ManualOff: Manual unit off.
• Auto1Off2: Automatic Circ#1, Circ#2 off.
• Auto2Off1: Automatic Circ#2, Circ#1 off.
• ManualStaging: Manual Staging, Circ#1 & 2.
Compressor Staging
The AGR chillers have two (2) refrigerant circuits, each circuit having a single reciprocating
compressor. When in the Automatic mode and stage 1 of cooling is required, the compressor with the
lowest number of starts will be the first compressor to start. Stage 2 of cooling will start the second
compressor. Subsequent staging requirements will load and unload compressor unloaders.
Head Pressure Control
There are two condenser fans per refrigerant circuit. These fans are cycled on and off according to
the circuit’s condenser pressure. Fan #1 of circuit will start when a compressor in the circuit has
started and the condenser pressure exceeds fan on setpoint (230psig R-22). This fan will not cycle off
until the circuit is stopped. The second fan will cycle on and off to maintain minimum lift pressure. If
the condenser pressure increases rapidly, the second fan will be turned on at 290psig
(R-22 setpoint) and remain on until minimum lift pressure regains control.
Pumpdown Control
The units have limited recycling pump down. The pumpdown setpoint will vary depending on the
refrigerant used.
Alarm conditions will not permit chiller pumpdown.
Safety Systems
MicroTech continuously performs self-diagnostic checks, monitoring all system temperatures,
pressures and safeties, and will automatically shut down a refrigerant circuit or the entire unit should a
fault occur. The cause of the shutdown, time and date of occurrence, and conditions at the time of
alarm will be retained in memory and can be displayed for the operator to review.
The MicroTech controller has several safety systems to safeguard against potential damage of the
chiller equipment. There are alarm and pre-alarm conditions. Alarm conditions cause the compressors
to shut off and/or lockout. Pre-alarm conditions cause the unit to stage down in capacity in an
attempt to avoid an alarm condition. For alarm conditions, the red “Alarm Status” light on the control
panel will be solid. For all pre-alarm conditions, the light will pulse at the rate of 0.5 seconds on, 4
seconds off. When an alarm of pre-alarm condition exists, the MicroTech display automatically
switches to the alarm menu to alert the user of the condition.