York YCAV0267E, Установка, эксплуатация и обслуживание

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38
JOHNSON CONTROLS
FORM 201.21-NM3 (616)
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 daily schedule
requires the unit to run or is overridden.
Unit Switch
Place the “Unit Switch” on the keypad to the ON posi-
tion.
Start-up
Press the SYSTEM SWITCHES Key and place the
system switch for System 1 to the ON position. 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 Switch OFF
immediately, if any unusual noises or other adverse
conditions develop.
When a compressor is running, the controller monitors
oil pressure, motor current, and various other system
parameters such as discharge pressure, chilled liquid
temperature, etc. Should any problems occur, the control
system will immediately take appropriate action and
display the nature of the fault.
Oil Pressure
When a compressor starts, press the relevant ‘System
Pressures’ key and verify that oil differential pressure
(oil pressure-suction 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 OFF position.
Refrigerant Flow
When a compressor starts, a flow of liquid refrigerant
will be seen in the liquid line sight glass. After several
minutes of operation, and provided a full charge of
refrigerant is in the system, the bubbles will disappear
and be replaced by a solid column of liquid.
Loading
Once the unit has been started, all operations are fully
automatic. After an initial period at minimum capacity,
the control system will adjust the unit load depending
on the chilled liquid temperature and rate of temperature
change. If a high heat load is present, the controller will
increase the speed of the compressor(s).
Condenser and Fan Rotation
Once a compressor is running, discharge pressure rises
as refrigerant is pumped into the air-cooled condenser
coils. This pressure is controlled by stages of fans to
ensure maximum unit efficiency while maintaining suf -
ficient pressure for correct operation of the condensers
and the lubrication system.
As discharge pressure rises, the condenser fans operate
in stages to control the pressure. Verify that the fans
operate in the correct direction of rotation and operation
is correct for the type of unit.
Suction Superheat
Check suction superheat at steady full compressor load
only. Measure suction temperature with a thermocouple
on the copper line about 6” (150 mm) before the com-
pressor suction service valve. Measure suction pressure
at the suction transducer access valve or the compressor
suction service valve. Superheat should be 10°F to 12°F
(5.55 to 6.67°C) and should be reasonably close to the
panel display. Superheat setting is programmable on
the control panel, but is not mechanically adjustable.
The Flash Tank Drain Valve controller modulates the
2-phase drain valve stepper motor to control system
superheat. Superheat control is a function of suction
pressure and suction temperature measurements from
the sensors that are routed to the Chiller Control Board
which in turn sends control signals to the Flash Tank
Drain and Fill Valve Controller located in the left, back
wall of the Chiller Controls Cabinet.
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 at the main liquid line service valve. Mea-
sure liquid pressure at the liquid line service valve.
Subcooling should be 5 - 7°F (2.77 - 3.88°C) . YCAV
0157 subcooling should be 10 °F (5.55°C). No bubbles
should show in the sight glass. If subcooling is out of
range, add or remove refrigerant as required to clear
the sight glass. Do not overcharge the unit. Subcooling
should be checked with a flash tank level of approxi -
mately 35% with a clear sight glass.
COMMISSIONING