Temperature Thermistors; Thermistor Sensor Comparison; Failed Thermistor Default Operation - Bryant Base Series Application Manual And Service Manual

Residential Air Conditioners and Heat Pumps Using R-22 and Puron® Refrigerant: Application Guideline and Service Manual

Temperature Thermistors

Thermistors are electronic devices which sense temperature. As the
temperature increases, the resistance decreases. Thermistors are used to
sense outdoor air (OAT) and coil temperature (OCT). Refer to
for resistance values versus temperature.
If the outdoor air or coil thermistor should fail, the control will flash the
appropriate fault code. (See Table
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. 45 and

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:
• In cooling if the outdoor air sensor indicates  10_F warmer than
the coil sensor (or) the outdoor air sensor indicates  20_F cooler
than the coil sensor, the sensors are out of range.
• In heating if the outdoor air sensor indicates  35_F warmer than
the coil sensor (or) the outdoor air sensor indicates  10_F cooler
than the coil sensor, the sensors are out of range.
Fig. 45 – Outdoor Air Thermistor (OAT) Attachment
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
18)
Fig. 46.
If the sensors are out of range, the control will flash the appropriate fault
code as shown in Table
The thermistor comparison is not performed during low ambient cooling
or defrost operation.
Fig. 41

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 18
error.
Fig. 46 – Outdoor Coil Thermistor (OCT) Attachment
A12263
60
18.
gives possible causes and actions related to each
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