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IOMM ACZ/AGZ-1
to the leaving water setpoint. This will be the day operating setpoint. This value cannot be reset
when in the day mode by any other reset options.
The alarm setpoints must be adjusted to allow operation of the chiller at the lower temperatures. The
following values should be adjusted and the example assumes 30% ethylene glycol solution with a
21°F shut down temperature:
1.
“FrzStat” Set to the saturated suction pressure that corresponds to a temperature several degrees
higher than the freeze point of the water / glycol solution. (10°F = 33psig.)
2.
“Frz H2O” Set at least 4°F below the shut down temperature, but not lower than the freezing
point of the water / glycol solution. (21°F - 4°F = 17°F)
3.
“LP cutout” Set 8 to 10 psi below the “Frz State” pressure but never below 20 psig. (33psi - 10 psi
= 23 psi)
4.
“LP Cutin” Set to a saturated suction pressure equal to the shut down temperature plus 1/2 the
control band. (21°F + 2°F = 23°F; 23°F = 46psig)
Network
A network refers to a McQuay MicroTech control panel (CSC or RMS) that can provide controlling
functions to several McQuay chillers. One function is to control the chiller leaving water temperature
according to some control logic in the network control panel. The network control panel will control
the leaving water setpoint when the “Network” option in the chiller is selected. The network control
panel will send a signal that reflects 0 to 100% reset of the leaving water set point according to the
value entered into the “MaxChwRst” of the unit controller.
Soft Loading
Soft loading limits the number of available stages when the unit is started to prevent excessive power
consumption and possible overshoot of the leaving water temperature set point. Soft loading is in
effect whenever the unit is started from an “off” cycle. On initial start-up, the chiller will turn on the
chilled water pump and sample the loop water temperature for a time equal to the Load Delay set point
(“LoadDelay”). If cooling is required at the end of the time-delay, a start procedure is initiated. On
entering the “Stage mode” the controller starts a countdown timer to indicate how long the unit has
been in the cool stage mode. The number of stages allowed during soft loading is determined by the
Soft Load Maximum Stages (“SoftLdMaxStg”). The duration of the soft load sequence is determined
by the Soft Load Timer. If the Soft Load Timer is set to zero, no soft loading will take place. When the
soft load option is enabled, any time remaining in the Soft Load Timer will be displayed in the menu
Soft Load Set points under item “Time Left”. The following set points may be adjusted in
SoftLoadSpts menu:
•
Soft Load: This is the amount of time soft loading will be in effect after the controller begins
staging. If set to zero, soft loading is canceled.
•
SoftLdMaxStg: Determines the maximum number of cooling stages which may be energized while
soft loading is in effect.
•
LoadDelay: The amount of time allowed for the controller to sample the loop water temperature
before initiating cooling.
Summary of Contents for ACZ 045A
Page 6: ...6 IOMM ACZ AGZ 1 Figure 3 Clearance Requirements...
Page 27: ...IOMM ACZ AGZ 1 27 Figure 12 AGZ AM Single point Connection with FanTrol...
Page 28: ...28 IOMM ACZ AGZ 1 Figure 13 AGZ AM Single point Connection with SpeedTrol...
Page 29: ...IOMM ACZ AGZ 1 29 Figure 14 AGZ AM Unit Control Schematic UNT...
Page 30: ...30 IOMM ACZ AGZ 1 Figure 15 AGZ AM Staging Schematic UNT...
Page 31: ...IOMM ACZ AGZ 1 31 Figure 16 AGZ AM MicroTech Controller Schematic...
Page 32: ...32 IOMM ACZ AGZ 1 Figure 17 AGZ AM Unit Control Schematic MicroTech...
Page 33: ...IOMM ACZ AGZ 1 33 Figure 18 AGZ AM Staging Schematic MicroTech...
Page 34: ...34 IOMM ACZ AGZ 1 Figure 19 ACZ Field Connection Diagram No Capacity Control...
Page 35: ...IOMM ACZ AGZ 1 35 Figure 20 ACZ Field Wiring Diagram Capacity Control Staging...
Page 104: ...Post Office Box 2510 Staunton Virginia 24402 2510 USA 800 432 1342 www mcquay com...
