4
trip is a good example of the type of safety that acts directly. If
specified, there may be both sensor inputs and mechanical
switches monitoring some points.
Refer to Table 1 for set points, except for the settings supplied
with the machine documentation. Job documentation will take
precedence over these standard settings.
Temperature switches should be set in a temperature bath and
compared to an accurate standard or electronic thermometer.
Pressure switches should be set using an accurate gage and a
controlled pressure source.
Pressure transducers should be checked using an accurate
gage and a controlled pressure source.
Thermistor and RTD sensor panel readouts should be com-
pared to the temperature to which they are exposed. If possible,
hold the sensor in ambient air and compare the reading with an
accurate thermometer.
Mechanical interlock and limit switch operation must be con-
firmed by testing the actuator.
The turbine overspeed linkage should be tested before the tur-
bine is powered. The trip actuator in the shaft can only be tested
by running the turbine. Once the turbine can run, it should be
gradually brought up to trip speed. If the turbine fails to trip at
the trip speed, then it should be shut down immediately and not
be started until a turbine manufacturer’s representative corrects
the problem.
Motor Drive — Accurate communication between the con-
trols and the starter/VFD (variable frequency drive) must be con-
firmed by test. For equipment of the size and capacity of the
17DA chiller, it is likely that the control panel and the starter/
VFD will communicate through a data line, not through hard-
wired circuits. There may be an “Emergency Stop” button hard-
wired between the control panel and the starter.
Where the chiller controls and ancillary equipment controls
are connected to a building automation system via data lines, it
must be confirmed that the central system cannot override the
chiller safeties nor energize any chiller component directly. The
starter or VFD, in particular, must be protected from being ener-
gized by a command from anywhere other than the chiller con-
trols. With the starter in a safety mode or disconnected from the
motor, attempts to energize the starter should be made from the
building controls to confirm that the building control system can-
not energize the starter directly.
If the starter can be energized, reprogramming of the control
system is essential before the starter is put on-line. Accidental
starting of the motor could have extreme consequences to the
chiller.
The program correction should be made in the starter/VFD
control system rather than in the building control system so that
future updates to the building controls do not remove this
protection.
Gas Engine Drive — Engine drives will be tested and
started by the engine manufacturer's representative. Control in-
terfaces will be tested by the Carrier technician in co-operation
with the engine manufacturer's representative. A check list from
the engine manufacturer must be completed before the engine
service representative is called.
Turbine Drive — Turbines have their own safety systems
which should be tested according to the instructions found in
their manufacturer’s literature. If the manufacturer’s instructions
are not available, they must be obtained from the local Carrier
representative or from the turbine manufacturer.
Interlocks between the chiller controls and the turbine con-
trols must be tested. The chiller must energize a solenoid which
then allows the trip and throttle valve to be set. If the solenoid is
deenergized, then the turbine trip and throttle valve must imme-
diately close.
A feedback switch to the chiller controls is located on the trip
and throttle valve. The switch must close when the valve is
opened. This provides a RUN signal to the chiller controls which
will then start to load the compressor. If the trip and throttle
valve is closed by a trip from either the chiller or turbine con-
trols, then this switch will open. This is a signal to the chiller that
the turbine has tripped and the chiller will enter a safety shut-
down mode.
Other interlocks, signals and feedbacks will vary with the job.
Consult the job controls manual and the field control drawings
for the entire chiller and for the turbine.
All items on Pre-Start-Up Checklist must be completed be-
fore the turbine service representative is called.
Pumpout System — The low-pressure cutout should be
set at the saturated pressure of refrigerant R-134a at 34 F (1 C).
A manual bypass switch is required to allow complete evacua-
tion of the cooler. See Table 2.
Leak Test and Dehydration — Check the absolute
pressure on the refrigerant side of the machine. The final opera-
tion of the 17DA installation is to leak test the machine and de-
hydrate it to the point where it maintains a pressure of 0.21 psia
(1 kPa) (equivalent to 29.48 in. [749 mm] mercury vacuum ref-
erenced to a 30 in. [762 mm] barometer). Refer to the Leak Test-
ing and Chiller Dehydration sections on pages 15 and 16.
If the machine absolute pressure is higher than the above val-
ues, repeat the evacuation and dehydration pumpdown opera-
tions until the machine proves to have a leak rate or vacuum loss
at a rate less than 0.1 in. (2 mm) mercury column in 24 hours.
The oil will always contain a minimal amount of dissolved
refrigerant. It is normal for a refrigerant sensor to sense refriger-
ant if placed too near the vent caps. If the seal allows refrigerant
vapor to pass, a sensor located at floor level 3 to 4 ft (0.9 to
1.2 m) from the sump vent cap will be quickly triggered as the
heavy refrigerant vapor will drop into the sump and flow out the
vent cap to floor level.
Table 1 — Control Settings
CONTROL LOCATION
SETTING
English Metric
Low Chilled Water Temperature
Cutout
Cooler Water Box
36 F or 5 F lower than brine tem-
perature
2.2 C or 3 C lower than brine tem-
perature
High Discharge Gas Temperature
Cutout
Compressor End Wall 220 F 104 C
High Thrust Bearing Temperature Compressor Bearing Chamber 185 F 85 C
High Condenser Pressure Cutout Instrument Panel 185 psig 13.0 kg/sq cm
Low Cooler Pressure Cutout Instrument Panel
2 psi below design suction
pressure
0.14 kg/sq cm
Low Seal Oil Pressure Cutout Instrument Panel Trip 11 psid Trip 0.76 kg/sq cm
Low Bearing Oil Pressure Cutout Instrument Panel
Tr i p 8 p s i g
Reset 13 psig
Trip 0.56 kg/sq cm
Reset 0.90 kg/sq cm
Auxiliary Oil Pump Differential
Pressure Control
Instrument Panel
Stop 27 psid
Start 23 psid
Stop 1.90 kg/sq cm
Start 1.60 kg/sq cm
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