Carrier 30GTN Service And Troubleshooting Manual

Also see for 30GTN: Product data Installation instructions Installation instructions

Carrier 30GTN Service And Troubleshooting Manual Manual pdf 58 page image

REPLACING THERMISTORS T1, T5, T6, T7, AND T8 —Add a small amount of thermal conductive grease to ther-mistor well. Thermistors are friction-fit thermistors, whichmust be slipped into receivers located in the cooler leavingfluid nozzle for T1, in the cooler head for T5 and T6 (EXVunits only), and in the compressor pump end for T7 and T8(EXV units only).THERMISTORS T3 AND T4 — These thermistors are lo-cated on header end of condenser coil. They are clamped ona return bend.THERMISTOR/TEMPERATURE SENSOR CHECK — Ahigh quality digital volt-ohmmeter is required to perform thischeck.1. Connect the digital voltmeter across the appropriatethermistor terminals at the J8 terminal strip on the MainBase Board for thermistors T1-T6, T9, T10; or the J5 ter-minal strip on the EXV Board for thermistors T7 and T8(see Fig. 31). Using the voltage reading obtained, readthe sensor temperature from Tables 30A-31B. To checkthermistor accuracy, measure temperature at probe loca-tion with an accurate thermocouple-type temperature mea-suring instrument. Insulate thermocouple to avoid ambi-ent temperatures from influencing reading. Temperaturemeasured by thermocouple and temperature determinedfrom thermistor voltage reading should be close, ± 5° F(3° C) if care was taken in applying thermocouple andtaking readings.2. If a more accurate check is required, unit must be shutdown and thermistor removed and checked at a knowntemperature (freezing point or boiling point of water) us-ing either voltage drop measured across thermistor atthe J8 or J5 terminals, by determining the resistance withchiller shut down and thermistor disconnected from J8 orJ5. Compare the values determined with the value readby the control in the Temperatures mode using the Mar-quee display.12341234262524232221201918171615141312111098765 BLUBLUPNKPNKTB5TB5TB5TB55678T10T9REMOTE SPACE TEMP(ACCESSORY)56789101234123456123456214635 T5T3T4T6T2T1COOLER ENTERINGFLUID TEMPOUTDOOR-AIR TEMP(ACCESSORY)COOLER LEAVINGFLUID TEMPSATURATEDCONDENSING TEMP-CIRCUIT BSATURATEDSUCTION TEMP-CIRCUIT B*SATURATEDCONDENSING TEMP-CIRCUIT ASATURATEDSUCTION TEMP-CIRCUIT A*MAIN BASE BOARDJ8T1-T6, T9, T10 THERMISTORSJ5EXV BOARD12 11 10 9 8 7 6 5 4 3 2 112 11 10 9T88T7 7CKTA* CKTB*COMPRESSOR RETURN GAS TEMPT7, T8 THERMISTORS*Not used on FIOP (Factory-Installed Option) unit with TXV (Ther-mostatic Expansion Valve).Fig. 31 — Thermistor Connections to J5 and J8Processor Boards58