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Start/stop Schedule; Setpoint And Remote Offset; First Time Start Up; Interlocks - Quantech QTC4 STYLE A Series Installation Operation & Maintenance

Air-cooled screw liquid chillers with variable speed drive, 150 - 500 tons, 525 - 1750 kw, 2 compressor, 60 hz.
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FORM QTC4-NM1
ISSUE DATE: 4/2/2018
Page 140 for more details on programming the date
and time).

Start/Stop Schedule

Program the daily and holiday start/stop by pressing
the SCHEDULE key (See Date/Time and Schedule
Keys on Page 140 for more details on programming
the date and time).

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 Setpoints Key on
Page 132).

FIRST TIME START UP

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
operation to be set up correctly, and a
commissioning 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, etc. Should any problems occur; the con-
trol system will immediately take appropriate action
QUANTECH
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 compressor(s).

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.
Assure all checks are completed in the Equipment
Pre - Startup and Startup Checklist. The chiller is then
ready to be placed into operation.
SECTION 6 - COMMISSIONING
93
6

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