Dunham-Bush ACXi 165-5SP-LN, Installation, Operation And Maintenance Manual

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3.0 OPERATION
3.1 GENERAL
The unit should be started up only by a
refrigeration technician who is familiar with
accepted operation practices for refrigeration
systems.
Use small screw unit start-up report to record all
temperature, pressure, electrical readings and
control settings. A copy must be forwarded to
Dunham-Bush, Inc., before the warranty will be
honored.
3.2 UNIT PIPING
Each unit has a separate refrigerant circuit for
each compressor. See figure 3.2 for typical unit
piping schematic.
3.3 SYSTEM WATER FLOW
RATE
The quantity of chilled water being circulated
can be measured quite accurately (
±
5%) by
determining the water pressure drop through the
evaporator and reading GPM from the evaporator
pressure drop curve, Figure 3.3. Connect reliable
pressure gauges to valves installed in evaporator
entering and leaving water vent connections and
read pressure difference with chilled water pump
in operation. An alternative method of
determining GPM is to measure pressure
difference from pump inlet to outlet and read
GPM from pump curve.
3.4 STANDARD AMBIENT
UNIT OPERATION (65°F
MINIMUM AMBIENT)
INCLUDING OVERNIGHT
SHUT-DOWN AND
MORNING RESTART
Caution:
These units may equipped with
manifold installed manual discharge valve that
must be opened before attempting to start.
Important:
Do not use chilled water pump
operation via the flow switch or Aux. chilled
water pump contacts to start & stop this unit.
These are safety controls, not operational
controls.
3.4.1 AIR COOLED PACKAGE
CHILLER START-UP
The unit is ready for start-up when the
following procedures have been
completed.
1. Water piping for the evaporator is
installed and tested.
2. Electrical connections are made and
properly fused.
3. Unit has been leak tested. leaks
corrected, and charge completed.
4.
Compressor crankcase heater(s) has
been energized for a minimum of 24
hours.
5. Calibrated refrigerant gages have been
connected to the suction and discharge.
6. Turn on the chilled water pump, check
direction of rotation and adjust the
water flow through the evaporator to
the specified flow rate. Bleed off all
entrained air.
7. Manually energize the fan starters and
check the fan rotation. Fans should
pull air through the condenser coil and
discharge vertically upwards.
8. Check all refrigerant valves to be sure
they are open.
9. Proceed to System Start-up.
Compressor #1 will start in about 15
minutes & proceed to load up if leaving
water temperature is above setpoint.
Compressor #2 will follows as the
demand dictates.
3.5 SYSTEM START UP
1. Before starting the compressor(s), check
all three phases of supply voltage, of all
legs of the motor. They must be within
±10% of the nameplate voltage. Check to
be sure compressor is not running
backwards.
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