FORM NO.:6U6K-B01E-NB-EN
JOHNSON CONTROLS
98
UNIT OPERATING SEQUENCE
The operating sequence described below relates to operation on
a starting process after power has been applied, such as start-up
commissioning. When a compressor starts, internal timers limit
the minimum time before another compressor can start to 40
seconds (20-120 seconds, adjustable).
1.When power is applied to the system, the micro- processor
will perform a pre-check to ensure that the daily/holiday
schedule and any remote interlocks will allow the unit to run,
all safety cut-outs are satisfied and no faults are unsettled. Any
problems found by the pre-check will be displayed if present.
2.For the unit to run, there must be an ‘ON’ command given by
controller or BAS (Building Automation System) for the unit to
respond to. Once the unit is ON, the water pump contactor will
close instantly. The unit will then detect the status of the flow
switch to ensure sufficient liquid flow is supplied.
3.If no problems are present and duty is required the inverter
compressor will start. After an initial period of operation
with the inverter compressor, the control system will adjust
the unit load depending on the liquid temperature and rate of
temperature change. If high load is present, the controller will
increase the speed of the inverter compressor, or simply start-
up the next compressor. If very little load is present, the inverter
compressor may continue to operate or may simply stop. If
the latter is the case, one compressor will restart automatically
should the liquid temperature require.
4.When a compressor is running the controller monitors suction
pressure and various other system parameters such as discharge
pressure, liquid temperature, etc. Should any problems occur,
the control system will immediately take appropriate action and
display the nature of the fault.
5.The corresponding condenser fan will be cycled on when
compressor starts. See the section on
EC Fan Control
for details
concerning condenser fan cycling.
6.Each system is fitted with an EEV (electrical expansion
valve) in the liquid line between condenser coil and cooler. The
device will automatically adjust the steps to satisfy refrigerant
flow demand, based on the difference between actual and target
superheat. There is a pre-adjustment of the opening before
compressor loading up or shutting down within one refrigerant
circuit.
7.If demand requires, another system (for dual circuit units), or
another unit (for modular control), will cycle on with the same
timing sequences as the inverter system. Refer to the section on
Liquid Temp. Control
for a detailed explanation of system and
compressor staging.
8.As the load decreases below setpoint, the compressors will
be shut down in sequence. This will normally occur at intervals
of 40 seconds based on water temperature as compared to set-
point and the rate of temperature change. See the section on
Liquid Temp. Control
for a detailed explanation.
9.When the last compressor in a “system” (one or two
compressors per system), is to be cycled off, the system will
switch off its fan and EEV shortly afterwards.
10.The unit can be stopped at any time by switching. The
compressor heaters will energize to prevent refrigerant
condensing in the compressor rotors and to prevent the
compressor oil becoming saturated with refrigerant.
11.If mains power must be switched off (for extended
maintenance or a shutdown period), the compressor suction
and discharge service valves on both systems should be closed
(clockwise) and if there is a possibility of liquid freezing due
to low ambient temperatures, the heat exchanger should be
drained. The valves should be opened, the heat exchanger
refilled and the power must be switched on for at least 8 hours
before the unit is restarted.
HYDRO KIT COMMISSIONING
The variable speed pump is already configured for end
customer use and no additional adjustments are necessary
after installation. Contact local JCI representatives if any
reconfiguration is required.
CIRCULATION PUMP
The high-efficiency pumps are glanded pumps with built-
in power adjustment and “Electronic Commutated Motor”
(ECM) technology. The pumps are designed as single-stage
SECTION 6 – COMMISSIONING
Cooke Industries - Phone: +64 9 579 2185 Email: [email protected] Web: www.cookeindustries.co.nz
