Carrier GTR040-420 Spezifikationen PDF herunterladen (Seite 69)

30GTN,R and 30GUN,R 130-210, 230A-315A and

330A/B-420A/B — A control relay in conjunction with a

ground fault module replaces the function of the CPCS

(above). To reset, press the push-button switch (near the

Marquee display).

LOW OIL PRESSURE PROTECTION — Lead compres-

sor in each circuit is equipped with a switch to detect low oil

pressure. Switch is connected directly to processor board.

Switch is set to open at approximately 5 psig (35 kPa) and to

close at 9 psig (62 kPa) maximum. If switch opens when

compressor is running, CR or processor board stops all com-

pressors in circuit. During start-up, switch is bypassed for

2 minutes.

CRANKCASE HEATERS — Each compressor has a 180-w

crankcase heater to prevent absorption of liquid refrigerant by

oil in crankcase when compressor is not running. Heater power

source is auxiliary control power, independent of main unit

power. This assures compressor protection even when main

unit power disconnect switch is off.

COOLER PROTECTION

Freeze Protection

— Cooler can be wrapped with heater

cables as shown in Fig. 38, which are wired through an ambi-

ent temperature switch set at 36 F (2 C). Entire cooler is cov-

ered with closed-cell insulation applied over heater cables.

Heaters plus insulation protect cooler against low ambient tem-

perature freeze-up to 0° F (–18 C).

Low Fluid Temperature

— Main Base Board is programmed

to shut chiller down if leaving fluid temperature drops below

34 F (1.1 C) for water or more than 8° F (4.4° C) below set

point for brine units. The unit will shut down without a

pumpout. When fluid temperature rises to 6° F (3.3° C) above

leaving fluid set point, safety resets and chiller restarts. Reset is

automatic as long as this is the first occurrence.

Loss of Fluid Flow Protection

— Main Base Board contains

internal logic that protects cooler against loss of cooler flow.

Entering and leaving fluid temperature sensors in cooler detect

a no-flow condition. Leaving sensor is located in leaving fluid

nozzle and entering sensor is located in first cooler baffle space

in close proximity to cooler tubes, as shown in Fig. 38. When

there is no cooler flow and the compressors start, leaving fluid

temperature does not change. However, entering fluid temper-

ature drops rapidly as refrigerant enters cooler through EXV.

Entering sensor detects this temperature drop and when enter-

ing temperature is 3° F (1.6° C) below leaving temperature,

unit stops and is locked off.

Loss-of-Charge

— A pressure switch connected to high side

of each refrigerant circuit protects against total loss-of-charge.

Switch settings are listed in Table 36. If switch is open, unit

cannot start; if it opens during operation, unit locks out and

cannot restart until switch is closed. Low charge is also moni-

tored by the processor when an EXV is used. The loss-of-

charge switch is wired in series with the high-pressure switch

on each circuit’s lead compressor.

IMPORTANT: Never open any switch or disconnect that

deenergizes crankcase heaters unless unit is being serviced

or is to be shut down for a prolonged period. After a pro-

longed shutdown or service, energize crankcase heaters for

24 hours before starting unit.

IMPORTANT: If unit is installed in an area where ambi-

ent temperatures fall below 32 F (0° C), it is recom-

mended that inhibited ethylene glycol or other suitable

corrosion-inhibitive antifreeze solution be used in chilled-

liquid circuit.

BLU

PNK

TB5

T10

REMOTE SPACE TEMP

(ACCESSORY)

COOLER ENTERING

FLUID TEMP

OUTDOOR-AIR TEMP

(ACCESSORY) OR

DUAL CHILLER LWT

COOLER LEAVING

FLUID TEMP

SATURATED

CONDENSING TEMP-

CIRCUIT B

SATURATED

SUCTION TEMP-

CIRCUIT B*

SATURATED

CONDENSING TEMP-

CIRCUIT A

SATURATED

SUCTION TEMP-

CIRCUIT A*

MAIN BASE BOARD

T1-T6, T9, T10 THERMISTORS

EXV BOARD

10 9

11 10 9

CKTA* CKTB*

COMPRESSOR RETURN GAS TEMP

T7, T8 THERMISTORS

LEGEND

*Not used on units with TXV (Thermostatic Expansion Valve) FIOP

(Factory-Installed Option).

Fig. 37 — Thermistor Connections to J5 and J8

Processor Boards

LWT —

Leaving Fluid Temperature

LEGEND

T —

Thermistor

Fig. 38 — Cooler Heater Cables

1 2 ... 64 65 66 67 68 69 70 71 72 73 74 ... 103 104

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