Bryant 598B Thermistor Curve, I. Pressure Switch Protection, J. Major Components, Control Board

I. PRESSURE SWITCH PROTECTION

The outdoor unit is equipped with high- and low-pressure switches. If the control senses the opening of a high or low pressure switch, it will respond as follows:

1.De-energize the compressor low or high speed contactor,

2.Keep the outdoor fan operating for 15 minutes,

3.Display the appropriate error code on the status light (see Table 5).

4.After a 15 minute delay, if Yl or Y2 inputs are on and the LPS or HPS is reset, energize appropriate compressor contactor, either low or high.

5.If LPS or HPS has not closed after a 15 minute delay, the outdoor fan is turned off. If the open switch closes anytime after the 15 minute delay, then resume operation on call for Y1 and/or Y2.

J.MAJOR COMPONENTS

TWO-SPEED CONTROL

The two-speed control board controls the following functions:

-Low- and high-compressor contactor operation

-Outdoor fan motor operation

-Crankcase heater operation

-Compressor protection

-Pressure switch monitoring

-Time delays

FIELD CONNECTIONS

The two-speed control received 24vac low-voltage control system inputs through the screw connections on the left side of the control board.

TWO-SPEED COMPRESSOR

The two-speed compressor contains motor windings that provide 2-pole (3500 RPM) operation.

COMPRESSOR INTERNAL RELIEF

The compressor is protected by an internal pressure relief (IPR) which relieves discharge gas into compressor shell when differen- tial between suction and discharge pressures exceeds 525 psi. The compressor is also protected by an internal overload attached to motor windings.

THERMISTOR CURVE

	90
(KOHMS)	80
	70
	60
RESISTANCE	50
	20
	40
	30

10

0

0 20 40 60 80 100 120

TEMPERATURE (DEG. F)

A91431

Fig. 13—Resistance Values Versus Temperature

COMPRESSOR CONTROL CONTACTORS

Low and high capacity contactor coils are 24 volts. The electronic control board controls the operation of the low speed (C-L) and the high speed (C-H) contactors.

K. TEMPERATURE THERMISTORS

Thermistors are electronic devices which sense temperature. As the temperature increases, the resistance decreases. Thermistors are used to sense outdoor ambient and coil temperature. Refer to Fig. 13 for resistance values versus temperature.

If the outdoor ambient or coil thermistor should fail, a fault code appears at two-speed control.

IMPORTANT: Outdoor Air Thermistor Placement Mount out- door air thermistor underneath unit base pan lip on control box side of the unit. Attach to base pan with adhesive tape.

IMPORTANT: If outdoor air thermistor is not properly placed underneath base pan, unit may see nuisance thermistor out of range faults.

Reversing Valve

Connection

Low/High Speed

Contactor Connection

SS0ID

HP/AC

C

SEV RVS

C

HI

LO

CEBD430439-03A

R38

C2

Low Pressure

J1

R33

R9

PL1

PL2

1

LPS

Switch Connector

R61

1

PL3

HPS

High Pressure

C31

Switch Connector

1

PL4

OAT

R65

DEFROST

FORCED

OCT

Thermistor

PL5

Connection

PWM2

DEFROST

Defrost Time 30

TIME (MIN)

60

R39

S1

120

R44

PWM1

R42

Selectors

60

1 2

30

C18

BRN

VC

R36

C16

To Run

90

BLU

0

VH

Capacitor

Y2

Thermostat

Y1

C O M M S T A T U S

BLK

ODF

W1

O.D.F. Connection

Low Voltage RC

D51

D52

CEPL130439-01

YEL

CCH L2

Connector

R85

R91

K1

RED

Crankcase Heater

R89

R86

R87

Connection

A

B

C D

H K 3 8 E A 0 0 1

Reserved for

Future Use

A01192

Fig. 12—Control Board

—13—