First Time Start-Up; Interlocks; System Switches; Start-Up - York YCAS Series Installation Operation & Maintenance

Commissioning

FIRST TIME START-UP

During the commissioning period
there should be suf fi cient heat load
to run the unit under sta ble full load
op er a tion to enable the unit con trols,
and sys tem op er a tion to be set up
cor rect ly and a com mis sion ing log
tak en. Be sure that the Micro Panel
is prop er ly pro grammed (page 178)
and the Sys tem Start-up Check list
(page 130) is com plet ed.

Interlocks

Verify that liquid is fl owing through the evaporator
and that heat load is present. Ensure that any remote
run in ter 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 mi cro pro ces sor board
to the 'ON' position – (Fig. 73, page 142).

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 fi rst
com pres sor starts be cause of the anti-recycle timer). Be
ready when each com pres sor starts, to switch the unit
OFF im me di ate ly if any unusual noises or other adverse
con di tions de vel op. Use the appropriate emergency stop
de vice if necessary.

Oil Pressure

When a compressor starts, press the rel e vant 'System
Pressures' key and verify that oil dif fer en tial pressure
develops immediately (Discharge Pressure minus
Section Pressure). If oil pressure does not develop,
the automatic controls will shut down the compressor.
Un der no cir cum stanc es should a restart attempt be made
on a com pres sor which does not develop oil pres sure
im me di ate ly. Switch the unit switch to the '0' po si tion
(OFF).

Refrigerant Flow

When a compressor starts a fl ow of liquid refrigerant
will be seen in the liquid line sight glass. After several
min utes operation and providing a full charge of
re frig er ant is in the system, the bubbles will disappear
and be re placed by a solid column of liquid.
42

Fan Rotation

As discharge pressure rises, the con dens er fans op er 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 tem per a ture on the copper line
about 6" (150 mm) before the compressor suc tion ser vice
valve. Measure suction pres sure at the com pres sor
service valve. Superheat should be 10°F to 12°F
(5.6°C to 6.7°C).

Expansion Valve

The electronic expansion valves are factory set and
should not need adjustment.

Economizer Superheat

(Not all models are equipped with economizers)
Check economizer su per heat at steady full com pres sor
load only, under conditions when the econ o miz er
solenoid is energized. (See Section 1.23, page 146)
Measure gas tem per a ture on the econ o miz er outlet
pipe next to the ex pan sion valve bulb. Mea sure gas
pressure at the back seat port of the economizer ser vice
valve. Su per heat as measured should be 10°F (5.6°C)
to 12°F (6.7°C).

Subcooling

Check liquid subcooling at steady full com pres sor
load only. It is important that all fans are run ning for
the sys tem. Measure liquid line temperature on the
copper line beside the main liquid line service valve.
Measure liq uid pressure at the liquid line service valve.
Subcooling should be 12°F to 15°F (6.7°C to 8.3°C).
No bubbles should show in the sight glass. If subcooling
is out of range add or re move re frig er ant as required.
Do not over charge the unit. The liq uid fl ow to the main
evaporator TXV is subcooled fur ther by the econ o miz er,
increasing subcooling to be tween 22°F and 28°F (-12°C
and -15°C) at ambients above 90°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 rect ly, stop the
unit, switch all applicable switch es to the 'ON' po si tion
and restart the unit.
FORM 201.19-NM8 (804)
YORK INTERNATIONAL