automatic through the ambient sensing
thermostat that energizes the evaporator heater
cable for protection against freeze-up. Unless
Operating/Standby Limits
Maximum standby ambient air temperature, 130F (55C)
Maximum operating ambient air temperature 105 F (40.6 C)
Minimum operating ambient temperature (standard), 35F (2C)
Minimum operating ambient temperature (with optional low-ambient control), -10F (-23.3C)
Leaving chilled water temperature, 40F to 60F (4.4C to 15.6C)
Leaving chilled fluid temperatures (with anti-freeze), 15F to 60F (-9.4C to 15.6C)
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, 76F (24C)
Maximum non-operating inlet fluid temperature, 100F (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.
OMM 1166-1
the evaporator is drained in the winter, the
disconnect switch to the evaporator heater
must not be open.
AGZ 025D through 190D
9