First Time Start-Up - York YCAS0098EB Installation Operation & Maintenance

FIRST TIME START-UP

During the commissioning period
there should be sufficient heat load
to run the unit under stable full load
operation to enable the unit controls,
and system operation to be set up cor‑
rectly and a commissioning log taken.
Be sure that the Micro Panel is prop‑
erly programmed (page 160) and the
System Start‑up Checklist (page 116)
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' switch on the microprocessor board
to the 'ON' position – see loading/unloading sequence
(Fig. 46, page 148).
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 because of the anti-recycle timer). Be ready when
each compressor starts, to switch the unit OFF immedi-
ately 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 pressure
immediately. Switch the unit switch to the '0' position
(OFF).
Refrigerant Flow
When a compressor starts a flow of liquid refrigerant
will be seen in the liquid line sight glass. 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.
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Fan Rotation
As discharge pressure rises, the condenser fans operate
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 6" (150 mm) before the compressor suction
service valve. Measure suction pressure at the compres-
sor service valve. Superheat should be 10°F to 12°F
(7 to 8°C).
Expansion Valve Adjustment
The expansion valves are factory set and should not need
adjustment. If any superheat values are out of range,
however, the expansion valve adjusting screw should be
adjusted no more than 1 turn at a time ('in' to increase
superheat, 'out' to decrease superheat), allowing at least
10 minutes for the valve to stabilize before rechecking
the value of superheat.
Economizer Superheat
(Not all models are equipped with economizers)
Check economizer superheat at steady full compressor
load only. Measure gas temperature on the economizer
outlet pipe next to the expansion valve bulb. Measure
gas pressure at the back seat port of the economizer
service valve. Superheat as measured should be 10°F
to 12°F (-7°C to -6°C).
Subcooling
Check liquid subcooling at steady full compressor
load only. It is important that all fans are running for
the system. 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 12°F to 15°F (-8°C to -7°C). No
bubbles should show in the sight glass. 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,
increasing subcooling to between 22°F and 28°F (-15°C
and -12°C).
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 process for
each subsequent system. When all run correctly, stop the
unit, switch all applicable switches to the 'ON' position
and restart the unit.
JOHNSON CONTROLS
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