16
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:
S
In cooling if the outdoor air sensor indicates
10
_
F (
5.6
_
C)
warmer than the coil sensor (or) the outdoor air sensor indicates
25
_
F (
12
_
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 comparisons are not performed during low ambient
cooling.
Outdoor Coil Thermistor
The outdoor coil thermistor is a 10Kohm resistor used for multiple
system operations. It provides the coil/liquid line temperature to
the AC unit board and user interface. Low ambient operation, and
assistance with OAT temperature measurement are some of the
functions. The sensor must be securely mounted to the tube
connecting the coil and distributor.
See Fig. 30 for proper
placement. See Table 4 for proper resistances.
A14328
Fig. 30 -- Outdoor Coil Thermistor (OCT) Attachment
(On Distributor Tube)
OAT Thermistor must be locked in place with
spherical nib end facing towards the front of
the control box
A11142
Fig. 31 -- OAT Thermistor Location (Bottom of Control Box)
Suction Thermistor (OST)
Suction Thermistor is used to accurately measure suction
temperature and must be secured on the suction tube and aligned
longitudinally to the vertical surface of the tube axis (see Fig. 32).
CAUTION
!
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment
damage or improper operation.
In order to minimize the ambient influence, make sure the
thermistor curved surface hugs the pipe surface and is
secured tight using the wire tie fished through the original
slot insulating polymer body.
A14023
Fig. 32 -- Suction Thermistor (OST) Attachment
(On Suction Tube)
Discharge Thermistor (ODT)
Discharge Thermistor is used for protection against over
temperature of the compressor.
The ODT is located on the
compressor discharge stub--out (see Fig. 33).
A14024
Fig. 33 - Discharge Thermistor (ODT)
