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Commissioning
Setpoint and Remote Offset
Set the required leaving chilled liquid temperature set-
point and control range. If remote temperature reset
(offset) is to be used, the maximum reset must be pro-
grammed by pressing the 'Remote Reset Temp' key.
(See Section 9 [6.1].)
FIRST TIME START-UP
During the commissioning period
there should be sufficient heat load to
run the unit under stable full load op-
eration to enable the unit controls, and
system operation to be set up correctly
and a commissioning log taken. Be
sure that the Micro panel is properly
programmed (page 142) and the Sys-
tem Startup Checklist (page 98) is
completed.
Interlocks
Verify that liquid is flowing through the cooler and that
heat load is present. Ensure that any remote run inter-
locks are in the run position and that the run schedule
requires the unit to run or is overridden.
System Switches
Place the 'Sys 1' and 'Sys 2' switches on the micropro-
cessor board to the 'ON' position – see Figure 36, page
109.
Start-Up
Remove the locking device from the unit Auto/OFF switch
which prevents unauthorized starting of the unit before
commissioning. Press the 'Status' key, then turn the unit
switch to the "1" position to start the unit (there may be a
few seconds delay before the first compressor starts be-
cause of the anti-recycle timer). Be ready when each
compressor starts, to switch the unit OFF immediately if
any unusual noises or other adverse conditions develop.
Use the appropriate emergency stop device if necessary.
Oil Pressure
When a compressor starts, press the relevant 'System
Pressures' key and verify that oil differential pressure
develops immediately. If oil pressure does not develop,
the automatic controls will shut down the compressor.
Under no circumstances should a restart attempt be
made on a compressor which does not develop oil pres-
sure immediately. Switch the unit switch to the '0' posi-
tion (OFF).
44
Refrigerant Flow
When a compressor starts, a flow of liquid refrigerant
will be seen in the liquid line sightglass. After several
minutes operation, and providing a full charge of refrig-
erant is in the system, the bubbles will disappear and be
replaced by a solid column of liquid.
Fan Rotation
As discharge pressure rises, the condenser fans oper-
ate in stages to control the pressure. Verify that the fan
operation is correct for the type of unit.
Suction Superheat
Check suction superheat at steady full compressor load
only. Measure suction temperature on the copper line
about 150 mm (6") before the compressor suction ser-
vice valve. Measure suction pressure at the compressor
service valve. Superheat should be -8°C to -7°C (12°F
to 15°F), preferably 15°F for typical applications which
cycle frequently.
Expansion Valve Adjustment
The expansion valves are factory set and should not
need adjustment. If any superheat values are out of range,
the expansion valve adjusting screw should be adjusted
no more than 1 turn at a time ('in' to increase super-
heat, 'out' to decrease superheat), allowing at least 10
minutes for the valve to stabilize before rechecking the
value of superheat.
Subcooling
Check liquid subcooling at steady full compressor load
only. It is important that all fans are running for the sys-
tem. Measure liquid line temperature on the copper line
beside the main liquid line service valve. Measure liquid
pressure at the liquid line service valve. Subcooling
should be -8°C to -7°C (12°F to 15°F). No bubbles
should show in the sightglass. If subcooling is out of
range add or remove refrigerant as required. Do not
overcharge the unit. The liquid flow to the main cooler
TXV is subcooled further by the economizer, increas-
ing subcooling to between -15°C and -12°C (22°F and
28°F).
General Operation
After completion of the above checks for System 1,
stop the unit, switch OFF the 'SYS 1' switch on the
main panel microprocessor board and repeat the pro-
cess for each subsequent system. When all run cor-
rectly, stop the unit, switch all applicable switches to the
'ON' position and restart the unit.
FORM 150.52-NM2 (1001)
YORK INTERNATIONAL
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