Bryant 280ANV Pressure Switch Protection, Control Fault, Brown-Out Protection

Pressure Switch Protection

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

1.De-energize the contactor.

2.Keep the outdoor fan operating for 15 minutes.

3.Display the appropriate fault code (see Table 7).

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

5.If 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 cool- ing or heating at a temporary reduced capacity.

6.If 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 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 7). The control board should be replaced.

Brown-Out Protection

If the line voltage is less than 187v for at least 4 seconds, the 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 7).

230V Line (Power Disconnect) Detection

If there is no 230v at the contactor when the indoor unit is powered with a cooling or heating demand, the appropriate fault code is displayed. Verify the disconnect is closed and 230v wiring is connected to the unit.

Inverter Voltage Sensing

The control board senses the presence or absence of 230 V through the feedback from inverter. The control monitors the high voltage to the inverter. Voltage should be present anytime the contactor is energized and voltage should not be present when the contactor is de-energized.

Temperature Thermistors

Thermistors are electronic devices which sense temperature. As the temperature increases, the resistance decreases. Thermistors are used to sense outdoor air (OAT), coil temperature (OCT) and the suction line thermistor (OST) located between the reversing valve and the accumulator.

Refer to Table 4 and Fig. 14 for resistance values versus temperature.

Table 4 – Resistance Values versus Temperature

TEMPERATURE	RESISTANCE (ohms)
25.0° C (77.0° F)	10.0 + / - 2.3%
0.0° C (32.0° F)	32.6 + / - 3.2%
-28.0° C (-18.4° F)	85.5 + / - 3.4%

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. 14 - Thermistor Resistance Versus Temperature

If the outdoor air or coil thermistor should fail, the control will flash the appropriate fault code (see Table 7.)

IMPORTANT: The outdoor air thermistor, coil thermistor and suction thermistor should be factory mounted in the final

locations. Check to ensure thermistors are mounted properly (See Fig. 15, 16 and 17).

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:

SIn cooling if the outdoor air sensor indicates ≥ 10_F (≥ 5.6_C) warmer than the coil sensor (or) the outdoor air sensor indicates ≥

20_F (≥ 11_C) cooler than the coil sensor, the sensors are out of range.

SIn heating if the outdoor air sensor indicates ≥ 35_F (≥ 19.4_C) warmer than the coil sensor (or) the outdoor air sensor indicates ≥ 10_F (≥ 5.6_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 7.

The thermistor comparisons are 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 (OAT) and/or outdoor coil thermistor (OCT).

If the OAT sensor should fail, low ambient cooling will not be allowed and the one-minute outdoor fan off delay will not occur. Defrost will be initiated based on coil temperature and time.

If the OCT sensor should fail, low ambient cooling will not be allowed. Defrost will occur at each time interval during heating operation, but will terminate after 5 minutes.

If there is a thermistor out-of-range error, defrost will occur at each time interval during heating operation, but will terminate after 5 minutes.

Count the number of short and long flashes to determine the appropriate flash code. Table 7 gives possible causes and actions related to each error.

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