Check Pressure Transducers - Carrier 19EF Series Start Up & Operation Manual

Periodically vacuum or blow off accumulated debris on
the internal parts with a high-velocity, low-pressure blower.
Power connections on newly installed starters may relax
and loosen after a month of operation. Turn power off and
retighten. Recheck annually thereafter.
Loose power connections can cause voltage spikes, over-
heating, malfunctioning, or failures.
Check Pressure Transducers —
pressure transducers should be checked against a pressure
gage reading. Check all three transducers: oil pressure, con-
denser pressure, cooler pressure.
Note the evaporator and condenser pressure readings on
the Status01 table on the LID. Attach an accurate set of re-
frigeration gages to the cooler and condenser Schrader fit-
tings. Compare the two readings. If there is a difference in
readings, the transducer can be calibrated, as described in
the Troubleshooting Guide section.
Ordering Replacement Chiller Parts —
dering Carrier specified parts, the following information must
accompany an order:
• machine model number and serial number
• name, quantity, and part number of the part required
• delivery address and method of shipment.
TROUBLESHOOTING GUIDE
Overview —
The PIC has many features to aid the op-
erator and the technician in troubleshooting a 19EF
machine.
• By using the LID display, the chiller actual operating con-
ditions can be viewed while the unit is running.
• When an alarm occurs, the default LID screen will freeze
at the time of alarm. The freeze enables the operator to
view the machine conditions at the time of alarm. The Sta-
tus tables will still show the current information. Once all
alarms have been cleared, the default LID screens will re-
turn to normal operation.
• The Control Test feature allows proper operation and
testing of temperature sensors, pressure transducers, the
guide vane actuator, oil pump, water pumps, tower con-
trol, and other on/off outputs while the compressor is stopped.
It also has the ability to lock off the compressor and turn
on water pumps for pumpout operation. The display will
show the required temperatures and pressures during these
operations.
• Other Service menu tables can access configured items,
such as chilled water resets, override set points, etc.
• If an operating fault is detected, an alarm message is gen-
erated and displayed on the LID default screen. A more
detailed message — along with a diagnostic message —
also is stored into the Alarm History table.
Checking the Display Messages —
to check when troubleshooting the 19EF is the LID display.
If the alarm light is flashing, check the primary and second-
ary message lines on the LID default screen (Fig. 10). These
messages will indicate where the fault is occurring. The Alarm
History table on the LID Service menu will also carry an
alarm message to further expand on this alarm. For a com-
plete listing of messages, see Table 9. If the alarm light starts
to flash while accessing a menu screen, depress EXIT to
return to the Default screen to read the failure message. The
compressor will not run with an alarm condition existing,
unless the alarm type is an unauthorized start or a failure to
shut down.
Checking Temperature Sensors —
ture sensors are of the thermistor type. This means that the
resistance of the sensor varies with temperature. All sensors
have the same resistance characteristics. Determine
sensor temperature by measuring voltage drop if the con-
trols are powered, or resistance if the controls are powered
off. Compare the readings to the values listed in Table 10A
or 10B.
RESISTANCE CHECK — Turn off the control power and
disconnect the terminal plug of the sensor in question from
the module. Measure sensor resistance between receptacles
Once a year, the
designated by the wiring diagram with a digital ohmmeter.
The resistance and corresponding temperature is listed in Table
10A or 10B. Check the resistance of both wires to ground.
This resistance should be infinite.
VOLTAGE DROP — Using a digital voltmeter, the voltage
drop across any energized sensor can be measured while the
control is energized. Table 10A or 10B lists the relationship
between temperature and sensor voltage drop (volts dc mea-
sured across the energized sensor). Exercise care when mea-
suring voltage to prevent damage to the sensor leads, con-
nector plugs, and modules. Sensor wire should also be checked
When or-
at the sensor plug connection. Check the sensor wire by re-
moving the condenser at the sensor and measure for 5 vdc
back to the module if the control is powered.
CHECK SENSOR ACCURACY — Place the sensor in a
medium of a known temperature and compare that tempera-
ture to the measured reading. The thermometer used to de-
termine the temperature of the medium should be of labo-
ratory quality with 0.5° F (.25° C) graduations. The sensor
in question should be accurate to within 2° F (1.2° C).
directly in the refrigerant or water circuits. The wiring at each
sensor is easily disconnected by unlatching the connector.
These connectors allow only one-way connection to the sen-
sor. When installing a new sensor, apply a pipe sealant or
thread sealant to the sensor threads.
DUAL TEMPERATURE SENSORS — There are 2 sensing
elements on each of the bearing and motor temperature sen-
sors for servicing convenience. In case one of the dual sen-
sors is damaged, the other one can be used by moving a wire.
common line. To use the second sensor, move the wire from
the number 2 position to the number 3 position.
Checking Pressure Transducers —
sure transducers on the 19EF. These determine cooler, con-
denser, and oil pressure. The cooler and condenser transduc-
ers also are used by the PIC to determine the refrigerant
temperatures. All 3 can be calibrated if necessary. It is not
usually necessary to calibrate at initial start-up. However, at
high altitude locations, calibration of the transducer will be
The first area
necessary to ensure the proper refrigerant temperature/
pressure relationship. Each transducer is supplied with
5 vdc power from a power supply. If the power supply fails,
a transducer voltage reference alarm will occur. If the trans-
ducer reading is suspected of being faulty, check the supply
voltage. It should be 5 vdc ± .5 v. If the supply voltage is
correct, the transducer should be recalibrated or replaced.
53
Relieve all refrigerant pressure or drain the water prior
to replacing the temperature sensors.
See Fig. 5 for sensor locations. The sensors are immersed
The number 1 terminal in the sensor terminal box is the
IMPORTANT: Whenever the oil pressure or the cooler
pressure transducer is calibrated, the other sensor should
be calibrated to prevent problems with oil differential
pressure readings.
All tempera-
There are 3 pres-