Specifications

47
JOHNSON CONTROLS
Form 201.28-NM1.EN.PED/CE (0211)
6
Setpoint and Remote Offset
Set the required leaving chilled liquid temperature setpoint
and Control Range under the SETPOINTS key. The
chilled liquid temperature control settings need to be set
according to the required operating conditions.
If remote temperature reset (offset) is to be used, the
maximum reset required must be programmed by
pressing the SETPOINTS key (see Section 8 Setpoints
key).
FIRST TIME START
During the commissioning period there
should be suffi cient heat load to run the
unit under stable full load operation to
enable the unit controls, and system
operation to be set up correctly, and a
commissioning log taken.
Interlocks
Verify that liquid is flowing through the cooler and
that heat load is present. Ensure that any remote run
interlocks 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 position.
Startup
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.
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 sufficient
pressure for correct operation of the condensers and the
lubrication system.
As discharge pressure rises, the condenser fans operate
in stages or ramp up in speed to control the pressure.
Verify that the fans operate in the correct direction of
rotation and operation is correct for the type of unit.
System Charge
Check system charge at steady full compressor load only.
It is important that all fans are running for the system.
The refrigerant level in the evaporator should be about
in the middle of the sight glass. Unless levels are at the
bottom or the top of the sight glass, they should not cause
concern or require adding or removing charge.
General Operation
After completion of the above checks for System 1,
switch OFF the SYS 1 switch on the keypad 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.
Assure all checks are completed in the Equipment Pre
- Startup and Startup Checklist (found at the end of
this section). The chiller is then ready to be placed into
operation.