Operation - Daikin McQuay AGZ-D Operating And Maintenance Manual

4. Put both circuit #1 & #2 switches to the Pumpdown and Stop position.
5. Apply power to the unit. The panel Alarm Light will stay on until S1 is closed. Ignore the Alarm
Light for the check out period. If you have the optional Alarm Bell, you may wish to disconnect it.
6. Check at the power block or disconnect for the proper voltage and proper voltage between phases.
Check power for proper phasing using a phase sequence meter before starting unit.
7. Check for 120Vac at the optional control transformer and at TB-2 terminal #1 and the neutral block
(NB).
8. Check between TB-2 terminal #7 and NB for 120 vac supply for transformer #2.
9. Check between TB-2 terminal #2 and NB for 120 vac control voltage. This supplies the
compressor crank case heaters.
10. Check between TB-3 terminal #17 and #27 for 24 vac control voltage.

Operation

Hot Gas Bypass (Optional)
This option allows the system to operate at lower loads without excessive on/off compressor cycling.
The hot gas bypass option is required to be on both refrigerant circuits because of the lead/lag feature
of the controller.
This option allows passage of discharge gas into the evaporator inlet (between the TX valve and the
evaporator) which generates a false load to supplement the actual chilled water or air handler load.
Note: The hot gas bypass valve cannot generate a 100% false load.
The pressure regulating valves are a Sporlan HGBE-8-75/150-7/8 ODF on models AGZ 025 to 065 and
Sporlan HGBE-8-75/150-1 1/8 ODF on AGZ 070 to 190. They are factory set to begin opening at 100
psig (R-410A) and can be changed by changing the pressure setting. The adjustment range is 75 to 150
psig. To raise the pressure setting, remove the cap on the bulb and turn the adjustment screw
clockwise. To lower the setting, turn the screw counterclockwise. Do not force the adjustment beyond
the range it is designed for, as this will damage the adjustment assembly. The regulating valve opening
point can be determined by slowly reducing the system load while observing the suction pressure.
When the bypass valve starts to open, the refrigerant line on the evaporator side of the valve will begin
to feel warm to the touch.
The bypass piping also includes a solenoid valve that is controlled by the MicroTech III controller. It
is active when the first stage of cooling on a circuit is active.
The hot gas line may become hot enough to cause injury. Be careful during valve checkout.
VFD Low Ambient Control (Optional)
The optional VFD fan control is used for unit operation below 35F (2C) down to a minimum of
-10F (-23.3C). The control looks at the saturated discharge temperature and varies the fan speed to
hold the temperature (pressure) at the "target" temperature. This temperature is established as an input
to a setpoint screen labeled "Sat Condenser Temp Target".
Filter-Driers
Each refrigerant circuit is furnished with a full flow filter drier (AGZ 030C – 100C) or a replaceable
core type filter-drier (AGZ 140C – 180C). The core assembly of the replaceable core drier consists of
a filter core held tightly in the shell in a manner that allows full flow without bypass.
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WARNING
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AGZ 025D through 190D OMM 1087