Carrier Performance 25HPA6 Installation Instructions Manual

Also see for 25HPA6: Wiring diagram

Contents

122. If the expected result is not achieved, remove the solenoidplug from the compressor and with the unit running and theUser Interface or thermostat calling for high stage, test thevoltage output at the plug with a DC voltmeter. The read-ing should be 24 volts DC.3. If the correct DC voltage is at the control circuit moldedplug, measure the compressor unloader coil resistance. Theresistance should be 32 to 60 ohms depending on com-pressor temperature. If the coil resistance is infinity, muchlower than 32 ohms, or is grounded, the compressor mustbe replaced.Temperature ThermistorsThermistors are electronic devices which sense temperature. As thetemperature increases, the resistance decreases. Thermistors areused to sense outdoor air (OAT) and coil temperature (OCT).Refer to Fig. 7 for resistance values versus temperature.01020304050607080900(-17.77)20(-6.67)40(4.44)60(15.56)80(26.67)100(37.78)120(48.89)TEMPERATURE °F (°C)RESISTANCE (KOHMS)THERMISTOR CURVEA08054Fig. 7 -- Resistance Values Versus TemperatureIf the outdoor air or coil thermistor should fail, the control willflash the appropriate fault code. (See Table 4.)IMPORTANT: The outdoor air thermistor and coil thermistorshould be factory mounted in the final locations. Check to ensurethermistors are mounted properly per Fig. 8 and Fig. 9.Thermistor Sensor ComparisonThe control continuously monitors and compares the outdoor airtemperature sensor and outdoor coil temperature sensor to ensureproper 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 sensorindicates ≥ 20_F (≥ 11_C) cooler than the coil sensor, thesensors are out of range.S In 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 outof range.If the sensors are out of range, the control will flash the appropriatefault code as shown in Table 4.The thermistor comparison is not performed during low ambientcooling or defrost operation.Failed Thermistor Default OperationFactory defaults have been provided in the event of failure ofoutdoor air thermistor (OAT) and/or outdoor coil thermistor(OCT).If the OAT sensor should fail, low ambient cooling will not beallowed 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 beallowed. Defrost will occur at each time interval during heatingoperation, but will terminate after 5 minutes.If there is a thermistor out of range error, defrost will occur at eachtime interval during heating operation, but will terminate after 5minutes.Count the number of short and long flashes to determine theappropriate flash code. Table 4 gives possible causes and actionsrelated to each error.OAT Thermistor must belocked in place with sphericalnib end facing towards thefront of the control boxFig. 8 -- Outdoor Air Thermistor (OAT) AttachmentOCT Thermistormust be securedtight on stub tube.Fig. 9 -- Outdoor Coil Thermistor (OCT) Attachment25HPA6