Carrier 23XL Dokumentacja Pobierz pdf (Strona 68)

Ordering Replacement Chiller Parts — When or-

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 23XL

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 Algorithm Status tables will display various

screens of information in order to diagnose problems with

chilled water temperature control, chilled water tempera-

ture control overrides, hot gas bypass, and time schedule

operation.

• The Control Test feature allows proper operation and test-

ing of temperature sensors, pressure transducers, the slide

valve solenoids, water pumps, tower control, 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 — The ﬁrst area

to check when troubleshooting the 23XL is the LID display.

If the alarm light is ﬂashing, check the primary and second-

ary message lines on the LID default screen (Fig. 17). 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 10. 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 con-

dition existing, unless the alarm type is an unauthorized start

or a failure to shut down.

Checking Temperature Sensors — All tempera-

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 Tables 11

and 12.

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

designated by the wiring diagram with a digital ohmmeter.

The resistance and corresponding temperature is listed in Tables

11 and 12. 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. Tables 11 and 12 list 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. Voltage should also be checked

at the sensor plugs. Check the sensor wire at the sensor for

5 vdc if the control is powered.

Relieve all refrigerant pressure or drain the water prior

to replacing the temperature sensors.

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).

See Fig. 11 and 12 for sensor locations. The sensors are

immersed 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 con-

nection to the sensor. When installing a new sensor, apply a

pipe sealant or thread sealant to the sensor threads.

DUAL TEMPERATURE SENSORS — Two motor tem-

perature sensors are provided for service convenience. In case

one of the dual sensors is damaged, the other one can be

used by moving a wire.

The number 1 terminal in the sensor terminal box is the

common line. To use the second sensor, move the wire from

the number 2 position to the number 3 position.

Checking Pressure Transducers — There are 3 pres-

sure transducers on the 23XL. These determine cooler, dis-

charge, and oil pressure. The PIC uses the discharge pres-

sure transducer to determine condenser pressure. The PIC

also determines refrigerant temperatures from cooler and con-

denser pressure. 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

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.

Calibration can be checked by comparing the pressure read-

ings from the transducer against an accurate refrigeration gage.

These readings are all viewed or calibrated from the Sta-

tus01 table on the LID. The transducer can be checked and

calibrated at 2 pressure points. These calibration points are

0 psig (0 kPa) and 250 ± 10 psig (1724 ± 69 kPa). To cali-

brate these transducers:

1. Shut down the compressor.

2. Disconnect the transducer in question from its Schrader

ﬁtting.

3. Access the Status01 table, and view the particular trans-

ducer reading; it should read 0 psig (0 kPa). If the read-

ing is not 0 psig (0 kPa), but within ± 5 psi (35 kPa), the

value may be zeroed by pressing the SELECT

softkey

while the highlight bar is located on the transducer, and

then by pressing the ENTER

softkey.

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