Bryant 286A Stage Control Board, Field Connections, Two Stage Compressor, Model Plug

MAJOR COMPONENTS

2-Stage Control Board

The HP control board controls the following functions:

SHigh and low stage compressor contactor operation S Outdoor fan motor operation

S Reversing valve operation S Defrost operation

S Low ambient cooling

S Crankcase heater operation

S Compressor external protection S Pressure switch monitoring

S Time Delays

S On 286A models, high- and low-stage start relay and capacitor operation (Bristol compressor only)

Field Connections

On models with non-communicating (non-Evolution) system, the two-stage control receives 24vac low-voltage control system inputs through the R, C, Y1, Y2 and O connections located at the bottom of the control board (see Fig. 6.) On a non-communicating system, output W1 is connected at the bottom of the control board for auxiliary heat.

On models with communicating system, use the ABCD Evolution connections.

Two Stage Compressor

The two stage compressor contains motor windings that provide 2-pole (3500 RPM) operation. For two-stage compressor, 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 the compressor shell when differential between suction and discharge pressure exceeds 500-550 psi on 286A models and 550-625 psi on 288A models. The compressor is also protected by an internal overload attached to motor windings.

Compressor Control Contactors

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

TROUBLESHOOTING

Systems Communication Failure

If communication with the Evolution control is lost with the User Interface, the control will flash the appropriate fault code. (See Table 6.) Check the wiring to the UI and the indoor and outdoor units.

Model Plug

Each control board contains a model plug. The correct model plug must be installed for or the system to operate properly. (See Table 4.)

Table 4 – Model Plug Information

MODEL	MODEL PLUG	PIN RESISTANCE
		(K---ohms)
NUMBER	NUMBER
		Pins 1---4	Pins 2---3
286A024	HK70EZ002	5.1	18
286A036	HK70EZ004	5.1	33
286A048	HK70EZ006	5.1	51
286A060	HK70EZ008	5.1	75
288A024	HK70EZ010	5.1	120
288A036	HK70EZ012	5.1	180
288A048	HK70EZ014	5.1	270
288A060	HK70EZ016	11	5.1

The model plug is used to identify the type and size of unit to the control. On 286A models, the model plug is also used to determine the start sequence timing for each individual model.

On new units, the model and serial numbers are input into the board’s memory at the factory. If a model plug is lost or missing at initial installation, the unit will operate according to the information input at the factory and the appropriate error code will flash temporarily. An RCD replacement board contains no model and serial information. If the factory control board fails, the model plug must be transferred from the original board to the replacement board for the unit to operate.

NOTE: The model plug takes priority over factory model information input at the factory. If the model plug is removed after initial power up, the unit will operate according to the last valid model plug installed, and flash the appropriate fault code temporarily.

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 appropriate compressor contactor.

2.Keep the outdoor fan operating for 15 minutes.

3.Display the appropriate fault code (see Table 6).

4.After a 15 minute delay, if there is a call for cooling or heat- ing and LPS or HPS is reset, the appropriate compressor contactor is energized.

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 with a call for cooling or heating.

6.If LPS or HPS trips 3 consecutive cycles, the unit operation is locked out for 4 hours.

7.In the event of a high-pressure switch trip or high-pressure lockout, check the refrigerant charge, outdoor fan operation, and outdoor coil (in cooling) for airflow restrictions, or in- door airflow in heating.

8.In the event of a low-pressure switch trip or low-pressure lockout, check the refrigerant charge and indoor airflow (cooling) and outdoor fan operation and outdoor coil in heating.

Control Fault

If the outdoor unit control board has failed, the control will flash the appropriate fault code (see Table 6). The control board should be replaced.

Brown-Out Protection

If the line voltage is less than 187v for at least 4 seconds, the appropriate compressor contactor and fan relay are de-energized. Compressor and fan operation are not allowed until voltage is a minimum of 190v. The control will flash the appropriate fault code (see Table 6).

230v Brown-Out Protection Defeated

The brownout feature can be defeated if needed for severe noisy power conditions. This defeat should always be a last resort to solving the problem. Defeat is available on the User Interface setup screen (available with SYSTXBBUID01-C UI) or can be initiated through the forced defrost pins for non-communicating systems as follows:

The brownout toggle is accomplished by shorting the defrost pins from power up with the OAT and OCT sensor connector removed. After 3 seconds, the status of the force defrost short and the OAT/OCT as open will be checked. If correct, then the brownout will be toggled.

SStatus code 6 shows the brownout is disabled. S Status code 5 shows the brownout is active.

After the brownout defeat is set, power down and reinstall the OAT/OCT sensor and remove the short from the forced defrost pins. As long as the short on the forced defrost remains, the OAT

286A / 288A

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