OMM 1166-1
AGZ 025D through 190D
9
automatic through the ambient sensing
thermostat that energizes the evaporator heater
cable for protection against freeze-up. Unless
the evaporator is drained in the winter, the
disconnect switch to the evaporator heater
must not be open.
Operating/Standby Limits
Maximum standby ambient air temperature, 130
F (55
C)
Maximum operating ambient air temperature 105
F (40.6
C)
Minimum operating ambient temperature (standard), 35
F (2
C)
Minimum operating ambient temperature (with optional low-ambient control), -10
F (-23.3
C)
Leaving chilled water temperature, 40
F to 60
F (4.4
C to 15.6
C)
Leaving chilled fluid temperatures (with anti-freeze), 15
F to 60
F (-9.4
C to 15.6
C)
Chilled water Delta-T range, 6 degrees F to 16 degrees F (3.3 degrees C to 8.9 degrees
C)
Part load minimum flow for variable flow systems, varies with unit size; see Table 8, page 11.
Maximum operating inlet fluid temperature, 76
F (24
C)
Maximum non-operating inlet fluid temperature, 100
F (38
C).
Pressure Drop Curves
Minimum Allowable Flow Rates
In order to maximize energy savings from variable flow systems, the AGZD chiller employs different
control strategies for constant-f low chilled water systems as compared to variable-flow systems.
A chiller controller setpoint selects the proper controller operation. The software setting of Variable
Evap. Flow equals YES or NO is located just below the “Full Cap D-T” setting screen.
The Full Cap D-T setting will continue to allow settings from 6 to 16 F Delta-T for full load operation.
Constant-Chilled Water Flow Systems
The minimum allowable flow is determined by the chiller model. Operating with flows below these
values can cause unstable operation.
Variable-Chilled Water Flow Systems
For models AGZ 025D through AGZ 130D the part load flow rate in a variable chilled water flow
system is 40% of nominal catalog
full load
flow (rated catalog tons x 2.4 = full load GPM). These
minimum allowable flows are calculated to allow the chilled water flow to decrease progressively as
the unit capacity decreases, but is restricted to 40% of rated full load flow.
The larger AGZ 140D to190D units have shell and tube evaporators and will operate at the same
minimum flow rate as for constant flow (62.5% of nominal catalog full load flow rate.)
When “Variable Evap Flow” is selected as YES – the unit software will increase the control band
progressively as the unit capacity steps to the lower stages of 75%, 50% and 25% load for the four
compressors. This prevents short cycling and allows for decreasing minimum water flow as the unit
capacity decreases. The 6 compressor units will have a similar operation but with software
calculations based on 6 capacity steps.
Refer to Table 8 on page 11 for the allowable reduced minimum flows.
Summary of Contents for AGZ 190D
Page 12: ...12 AGZ 025D through 190D OMM 1166 1 Figure 2 Typical Field Control Wiring...
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