JOHNSON CONTROLS
100
SECTION 6 - COMMISSIONING
Form 201.28-NM1.1
Issue date: 08/06/2021
First time startup
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 op-
eration to be set up correctly, and a com-
missioning log taken.
Interlocks
Verify that liquid is flowing through the evaporator
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 compres-
sor 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, and so on. 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 con-
trols will shut down the compressor. Under no circum-
stances should a restart attempt be made on a compres-
sor, 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 tempera-
ture change. If a high heat load is present, the control-
ler will increase the speed of the compressors.
Condenser and fan rotation
Once a compressor is running, discharge pressure
rises as refrigerant is pumped into the air-cooled con-
denser coils. This pressure is controlled by stages of
fans to ensure maximum unit efficiency while main-
taining 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.
Ensure all checks are completed in the Equipment
Pre - Startup and Startup Checklist. The chiller is then
ready to be placed into operation.
Freeze damage protection
Failure to follow the required freeze
protection protocols can void the factory
warranty
.
If the YVAA is exposed to subfreezing ambient tem-
peratures at any time during its life, it is critical to
protect against evaporator freeze damage. The YVAA
chiller can be equipped with features to prevent freeze
damage to the evaporator. These features require con-
tinuous power to the chiller control panel, chilled fluid
circuit pumps and evaporator heaters to prevent dam-
age from freezing. If continuous power cannot be guar-
anteed or chilled fluid flow cannot be provided during
periods of subfreezing ambient temperatures, then one
of the following freeze protection protocols must be
followed:
