Bryant 180A StageControl, Field Connections, StageCompressor, Compressor Internal Relief

Table 5 – 2---Stage Compressor

(Winding Resistance at 70_F ± 20_ / 21.11_C ± 11.11_C)

Winding	187A024	187A036	187A048	187A060
Start (S---C)	2.74	1.98	1.55	0.74
Run (R---C)	0.80	0.75	0.48	0.36
Winding	180A024	180A036	180A048	180A060
Start (S---C)	1.40	1.29	1.52	0.60
Run (R---C)	1.32	0.89	0.64	0.49

MAJOR COMPONENTS

2-Stage Control

The 2-stage control board controls the following functions:

-Low- and high-stage compressor contactor operation

-Outdoor fan motor operation

-Low ambient cooling

-Crankcase heater operation

-Compressor external protection

-Pressure switch monitoring

-Time delays

-On 187A models, start relay and capacitor

Field Connections

On 187A models with non-communicating (non-Evolution) system, the 2-stage control receives 24vac low-voltage control system inputs through the R, C, Y1, and Y2 connections located at the bottom of the control board (see Fig. 6). The 187A can be controlled using a standard 2-stage thermostat or Evolution User Interface.

All 180A models are part of a complete Evolution communicating system and use only the ABCD connections on the circuit board. The 180A must be controlled using an Evolution User Interface for proper equipment staging and operation

2-Stage Compressor

The 2-stage compressor contains motor windings that provide 2-pole (3500 RPM) operation. Refer to Table 5 for correct winding resistance.

Compressor Internal Relief

The compressor is protected by an internal pressure relief (IPR) which relieves discharge gas into compressor shell when differential between suction and discharge pressures exceeds 500 - 550 psi on 187A models and 550 - 625 psi on 180A models. The compressor is also protected by an internal overload attached to motor windings.

Compressor Control Contactors

The contactor(s) have a 24 volt coil. The electronic control board controls the operation of the appropriate contactors.

TEMPERATURE THERMISTORS

Thermistors are electronic devices which sense temperature. As the temperature increases, the resistance decreases. Thermistors are used to sense outdoor ambient (OAT) and coil temperature (OCT). Refer to Fig. 7 for resistance values versus temperature.

If the outdoor ambient or coil thermistor should fail, the control will flash the appropriate fault code (see Table 6.)

THERMISTOR CURVE

	90
(KOHMS)	80
	70
	60
RESISTANCE	50
	20
	40
	30
	10
	0

0	20	40	60	80	100	120
(-17.77)	(-6.67)	(4.44)	(15.56)	(26.67)	(37.78)	(48.89)
		TEMPERATURE °F (°C)

A08054

Fig. 7 - Resistance Values Versus Temperature

IMPORTANT: Outdoor air thermistor and coil thermistor are factory mounted in the final locations. Check to insure thermistors are mounted properly per Fig. 8 and Fig. 9.

Thermistor Sensor Comparison

The control continuously monitors and compares the outdoor air temperature sensor and outdoor coil temperature sensor to ensure proper operating conditions. The comparison is:

SIf the outdoor air sensor indicates ≥ 10_F/5.56_C warmer than the coil sensor (or) the outdoor air sensor indicates ≥ 20_F/11.11_C cooler than the coil sensor, the sensors are out of range.

If the sensors are out of range, the control will flash the appropriate fault code as shown in Table 6.

The thermistor comparison is not performed during low ambient cooling or defrost operation.

Failed Thermistor Default Operation

Factory defaults have been provided in the event of failure of outdoor air thermistor and/or coil thermistor.

If the OAT sensor should fail, low ambient cooling will not be allowed and the one-minute outdoor fan off delay will not occur.

If the OCT sensor should fail, low ambient cooling will not be allowed.

180A / 187A

11