Carrier 30GTR Specifications download pdf (Page 63)

Safety Devices — Chillers contain many safety de-

vices and protection logic built into electronic control. Fol-

lowing is a brief summary of major safeties.

COMPRESSOR PROTECTION

Circuit Breaker — One manual-reset, calibrated-trip mag-

netic circuit breaker for each compressor protects against over-

current. Do not bypass or increase size of a breaker to cor-

rect problems. Determine cause for trouble and correct before

resetting breaker. Circuit breaker must-trip amps (MTA) are

listed on individual circuit breakers, and on unit label

diagrams.

30GTN,R070 (50 Hz), 080-110 and 230B-315B Compres-

sor Protection Board (CPCS) — The CPCS is used to con-

trol and protect compressors and crankcase heaters. Board

provides following features:

• compressor contactor control

• crankcase heater control

• ground current protection

• status communication to processor board

• high-pressure protection

One large relay is located on CPCS board that controls

crankcase heater and compressor contactor. In addition, this

relay provides a set of contacts that the microprocessor moni-

tors to determine operating status of compressor. If the MBB

determines that compressor is not operating properly through

signal contacts, control locks compressor off.

The CPCS contains logic that can detect if current-to-

ground of any winding exceeds 2.5 amps; if so, compressor

shuts down.

A high-pressure switch with a trip pressure of

426 ± 7 psig (2936 ± 48 kPa) is mounted on each compres-

sor; switch setting is shown in Table 32. Switch is wired in

series with the CPCS. If switch opens, CPCS relay opens,

processor detects it through signal contacts, and compressor

locks off.Aloss-of-charge switch is also wired in series with

the high-pressure switch and CPCS.

If any of these switches opens during operation, the com-

pressor stops and the failure is detected by the MBB when

signal contacts open. If lead compressor in either circuit is

shut down by high-pressure switch, ground current protec-

tor, loss of charge switch, or oil pressure switch, all com-

pressors in the circuit are locked off.

30GTN,R130-210, 230A-315AAND 330A/B-420A/B — A

control relay in conjunction with a ground fault module re-

places the function of the CPCS (above). To reset, press the

push-button switch near the Marquee display).

Table 32 — Pressure Switch Settings,

psig (kPa)

SWITCH CUTOUT CUT-IN

High Pressure

426±7

(2936 ± 48)

320±20

(2205 ± 138)

Loss-of-Charge 7 (48.2) 22 (151.6)

LOW OIL PRESSURE PROTECTION — Lead compressor

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 re-

frigerant by oil in crankcase when compressor is not run-

ning. Heater power source is auxiliary control power, inde-

pendent of main unit power. This assures compressor protection

even when main unit power disconnect switch is off.

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 prolonged shutdown or service, energize crank-

case heaters for 24 hours before starting unit.

COOLER PROTECTION

Freeze Protection — Cooler can be wrapped with heater cables

as shown in Fig. 32, which are wired through an ambient

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

temperature freeze-up to 0° F (−18 C).

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

bient temperatures fall below 32 F (0° C), it is rec-

ommended that inhibited ethylene glycol or other suit-

able corrosion-inhibitive antifreeze solution be used in

chilled-liquid circuit.

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. Re-

set 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 de-

tect 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. 20. When there is no cooler ﬂow and the compressors

start, leaving ﬂuid temperature does not change. However,

entering ﬂuid temperature drops rapidly as refrigerant enters

cooler through EXV. Entering sensor detects this tempera-

ture drop and when entering 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 32. 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 monitored 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.

LEGEND

T—Thermistor

Fig. 32 — Cooler Heater Cables

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Carrier 30GTR Specifications Page 63

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