Bryant 187B Communication and Status Function Lights, Compressor Operation, Time Delays

187B / 180B

Communication and Status Function Lights

For Evolution Control Only, Green communications (COMM)Light

Green LED (COMM Light)

A green LED (COMM light) on the outdoor board (see Fig. 6) indicates successful communication with the other system products. The green LED will remain OFF until communications is established. Once a valid command is received, the green LED will turn ON continuously. If no communication is received within 2 minutes, the LED will be turned OFF until the next valid communication.

Amber Status Light

An amber colored STATUS light is used to display the operation mode and fault codes as specified in the troubleshooting section. See Table 6 for codes and definitions.

NOTE: Only one code will be displayed on the outdoor unit control board (the most recent, with the highest priority).

Utility Interface with Evolution Control

The utility curtailment relay should be wired between R and Y2 connections on the control board for Evolution Communicating Systems only (see Fig. 6). This input allows a power utility device to interrupt compressor operation during peak load periods. When the utility sends a signal to shut the system down, the User Interface will display, “Curtailment Active”.

Compressor Operation

The basic scroll design has been modified with the addition of an internal unloading mechanism that opens a by-pass port in the first compression pocket, effectively reducing the displacement of the scroll.

The opening and closing of the by-pass port is controlled by an internal electrically operated solenoid. The modulated scroll uses a single step of unloading to go from full capacity to approximately 67% capacity. A single speed, high efficiency motor continues to run while the scroll modulates between the two capacity steps.

Modulation is achieved by venting a portion of the gas in the first suction pocket back to the low side of the compressor, thereby reducing the effective displacement of the compressor. Full capacity is achieved by blocking these vents, thus increasing the displacement to 100%.

A DC solenoid in the compressor controlled by a rectified 24 volt AC signal in the external solenoid plug moves the slider ring that covers and uncovers these vents. The vent covers are arranged in such a manner that the compressor operates at approximately 67% capacity when the solenoid is not energized and 100% capacity when the solenoid is energized. The loading and unloading of the two step scroll is done “on the fly” without shutting off the motor between steps.

NOTE: 67% compressor capacity translates to approximately 75% cooling capacity at the indoor coil. The compressor will always start unloaded and stay unloaded for five seconds even when the thermostat is calling for high-stage capacity.

Crankcase Heater Operation

The crankcase heater is energized during off cycle below 65_F (18.33_C).

Outdoor Fan Motor Operation

The outdoor unit control energizes the outdoor fan any time the compressor is operating except for low-ambient cooling operation.

The outdoor fan remains energized if a pressure switch or compressor overload should open. Outdoor fan motor will continue to operate for one minute after the compressor shuts off when the outdoor ambient is greater than or equal to 100_F (37.78_C) to allow for easier starting during next cooling cycle.

On 187B models - The outdoor fan motor is a PSC type. A fan relay on the control board turns the fan off and on by opening and closing a high voltage circuit to the motor. It does not change speeds between low and high stage operation.

On 180B models - The outdoor fan is an ECM type. The motor control is continuously powered with high voltage. The motor speed is determined by electrical pulses provided by the PWM outputs on the control board. The ECM motor RPM adjusts to outdoor conditions as described in Table 3. The PWM output can be measured between the PWM1 and PWM2 terminals on the circuit board with a volt meter set to DC volts.

Table 3 – Outdoor Fan Motor PWM

Outdoor Temp (DC volts, Tolerance +/- 2%)

	LOW---STAGE	HIGH ---STAGE	LOW--- &
MODEL			HIGH ---STAGE
	(OAT≤104_F/40_C) (OAT≤104_F/40_C)
			(OAT>104_F/40_C)

180B036	9.06	10.23	11.90
NOTE:

For 180A models in low---ambient cooling, the PWM output for both high ---

and low---stage equals the value for low---stage operation below 55_F (12.8_C).

In low ambient cooling (below 55_F/12.78_C) on 187B and 180B models, the control board cycles the fan off and on.

Time Delays

The unit time delays include:

SFive minute time delay to start cooling or heating operation when there is a call from the thermostat or user interface. To

bypass this feature, momentarily short and release Forced Defrost pins.

SFive minute compressor re-cycle delay on return from a

brown-out condition.

STwo minute time delay to return to standby operation from last valid communication (with Evolution only).

SOne minute time delay of outdoor fan at termination of cooling mode when outdoor ambient is greater than or equal to 100_F (37.78_C).

SThere is no delay between staging from low to high and from high to low capacity. The compressor will change from low to high and from high to low capacity “on the fly” to meet the demand.

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