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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 the
accepted operation practices for refrigeration
systems.
Use the scroll unit start-up report, to record all
temperature, pressure, electrical readings and
control settings. A copy must be forwarded to
Dunham-Bush service department, before
warranty will be honored.
3.2 UNIT PIPING
See Figure 3.2.1 for typical unit piping
schematics.
3-3 AIR COOLED PACKAGES
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 gauges have been
connected to the suction and discharge ports.
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. Rotation can be changed on 3-
phase motors by interchanging only two wires
on the main terminal block.
8. Check all refrigerant valves to be sure they
are open.
9. Proceed to section 3.4 System Start-Up.
3.4 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.
2. Start compressor(s), check the gauges and
note if the pressures are within the prescribed
limits.
3. Check the refrigerant sight glass to be sure it
is free of bubbles. If not, charge as specified
per section 4.8 Charging.
4. Shut the compressor down and check the
compressor crankcase sight glass for oil level.
It should be between 1/2 to 3/4 of the
complete sightglass. If not, see Section 3.5
Lubrication.
5. Restart the compressor. After an hour of
operation the expansion valve superheat
setting should be checked, it should be
between 8°F [4.4°C] and 10°F [5.6°C] at full
load design conditions. In some instances, it
will be necessary to lower the superheat
setting to ensure proper distribution. Turn the
TX valve adjustment stem clockwise to
increase the superheat setting and
counterclockwise to decrease the setting. Be
sure and allow ample time between each
adjustment for the system to rebalance.
6. The temperature of the chilled water both in
and out, should be checked to insure the unit
is operating within the desired temperatures.
3.5 LUBRICATION
3.5.1 OIL LEVEL
A properly operated unit should run with
the compressor crankcase warm to touch.
Check oil level frequently to see that a
sufficient amount of oil remains in the
crankcase. Compressor oil level can be
checked by the sight glass. To make sure
that proper oil level is observe, operate
the compressor for 15 minutes, then stop
the compressor. Oil should appear from
1/2 to 3/4 in the sight glass with the
compressor stopped.
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