Carrier 30GTR Specifications download pdf (Page 15)

Thermostatic Expansion Valves (TXV) —

Model 30GTN,R040-110 units are available from the fac-

tory with conventional TXVs with liquid line solenoids. The

liquid line solenoid valves are not intended to be a mechani-

cal shut-off. When service is required, use the liquid line serv-

ice valve to pump down the system.

NOTE: This option is not available for modular units.

The TXV is set at the factory to maintain approximately

8 to 12° F (4.4 to 6.7° C) suction superheat leaving the cooler

by monitoring the proper amount of refrigerant into the cooler.

All TXVs are adjustable, but should not be adjusted unless

absolutely necessary. When TXV is used, thermistors T5,

T6, T7, and T8 are not required.

The TXV is designed to limit the cooler saturated suction

temperature to 55 F (12.8 C). This makes it possible for unit

to start at high cooler ﬂuid temperatures without overload-

ing the compressor.

Compressor Protection Control System (CPCS)

or Control Relay(CR) —

Each compressor has its own

CPCS module or CR. See Fig. 13 for CPCS module. The

CPCS or CR is used to control and protect the compressors

and crankcase heaters. The CPCS and CR provide the fol-

lowing functions:

• compressor contactor control/crankcase heater

• crankcase heater control

• compressor ground current protection (CPCS only)

• status communication to processor board

• high-pressure protection

One large relay is located on the CPCS board. This relay

controls the crankcase heater and compressor contactor, and

also provides a set of signal contacts that the microprocessor

monitors to determine the operating status of the compres-

sor. If the processor board determines that the compressor is

not operating properly through the signal contacts, it will lock

the compressor off by deenergizing the proper 24-v control

relay on the relay board. The CPCS board contains logic that

can detect if the current-to-ground of any compressor wind-

ing exceeds 2.5 amps. If this condition occurs, the CPCS

shuts down the compressor.

Ahigh-pressure switch is wired in series between the MBB

and the CR or CPCS. On compressor A1 and B1 a loss-of-

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

switch. If the high-pressure switch opens during operation

of a compressor, the compressor will be stopped, the failure

will be detected through the signal contacts, and the com-

pressor will be locked off. If the lead compressor in either

circuit is shut down by the high-pressure switch, loss-of-

charge switch, ground current protector, or oil safety switch,

all compressors in that circuit are shut down.

NOTE: The CR operates the same as the CPCS, except the

ground current circuit protection is not provided.

Compressor Ground Current Protection Board

(CGF) and Control Relay (CR) —

The 30GTN,R130-

210, and associated modular units (see Table 1) contain one

compressor ground current protection board (CGF) for each

refrigeration circuit. The CGF contains logic that can detect

if the current-to-ground of any compressor winding exceeds

2.5 amps. If this occurs, the lead compressor in that circuit

is shut down along with other compressors in that circuit.

Ahigh-pressure switch is wired in series between the MBB

and the CR or CPCS. On compressor A1 and B1 a loss-of-

charge switch is also included with the high-pressure switch.

The lead compressor in each circuit also has the CGF con-

tacts described above. If any of these switches open during

operation of a compressor, the CR relay is deenergized, stop-

ping the compressor and signaling the processor at the MBB-J9

inputs to lock out the compressor. If the lead compressor in

either circuit is shut down by high-pressure switch, com-

pressor ground fault, oil pressure switch, or the loss-of-

charge switch, all compressors in that circuit are also shut

down.

Fig. 13 — Compressor Protection Control

System Module

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Carrier 30GTR Specifications Page 15

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