Bryant 286A instruction manual Thermistor Sensor Comparison, Failed Thermistor Default Operation

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

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

IMPORTANT: The outdoor air thermistor and coil thermistor

should be factory mounted in the final locations. Check to ensure thermistors are mounted properly per Fig. 8 and Fig. 9.

OAT Thermistor must be locked in place with spherical nib end facing to- wards the front of the control box

Fig. 8 - Outdoor Air Thermistor (OAT) Attachment

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 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	288A
(OCT).
outdoor air thermistor (OAT) and/or outdoor 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.	286A
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 6 gives possible causes and actions
related to each error.
OCT Thermistor
must be secured
tight on stub tube.

Fig. 9 - Outdoor Coil Thermistor (OCT) Attachment

Table 5 – Two-Stage Compressor Resistances

(Winding Resistance at 70_F±20_F / 21_C±11_C)

Winding	286A024	286A036	286A048	286A060
Start (S-C)	2.74	1.98	1.55	0.74
Run (R-C)	0.80	0.75	0.48	0.36
Winding	288A024	288A036	288A048	288A060
Start (S-C)	1.40	1.29	1.52	0.60
Run (R-C)	1.32	0.89	0.64	0.49

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