Carrier 040-420 Installation And Service Manual

Thermistors - All thermistors are identical in their tem-perature vs. resistance performance. Resistance at varioustemperatures are listed in Tables 15 and 16.LOCATION - General location of thermistor sensors areshown in Fig. 13.Cooler Leaving Water Thermistor (Tl) - Tl is located inleaving water nozzle. The probe is immersed directly in thewater. All thermistor connections are made through a %-in.coupling. See Fig. 15. Actual location is shown in Fig. 13and 14.Cooler Entering Water Thermistor (T2) - T2 is located incooler shell in first baffle space near tube bundle. Ther-mistor connection is made through a %-in. coupling. SeeFig. 15. Actual location is shown in Fig. 13 and 14.Compressor Suction Gas Temperature Thermistors (T7 andT8) - T7 and T8 are located in lead compressor in eachcircuit in suction passage between motor and cylinders, aboveoil pump. They are well-type thermistors on 040-210 andassociated modular units, or ferrule-type on 225, 250, 280units. See Fig. 13 and 14.THERMISTOR REPLACEMENT (Tl , T2, T7, TS) (Com-pressor and Cooler)Thermistors are installed directly in fluid or refrigerantcircuit. Relieve all refrigerant pressure using standardrefrigerant practices or drain fluid before removing.Proceed as follows (see Fig. 15):To replace sensors Tl, T2, T7 (225,250,280), and T8(225,250,280)1. Remove and discard original thermistor and coupling.IMPORTANT: Do not disassemble new coupling.Install as received. I2. Apply pipe sealant to ‘/a-in. NPT threads on replace-ment coupling and install in place of original. Do notuse packing nut to tighten coupling. This damages fer-rules (see Fig. 15).3. Insert new thermistor in coupling body to its full depth.If thermistor bottoms out before full depth is reached,pull thermistor back out I/s in, before tightening packingnut. Hand tighten packing nut to position ferrules, thenfinish tightening 19’4 turns with a suitable tool. Ferrulesare now attached to thermistor which can be withdrawnfrom coupling for unit servicing.To replace thermistors T7 and T8 (040-210 and associatedmodular units):Add a small amount of thermal conductive grease to ther-mistor well. Thermistors are friction-fit thermistors, whichmust be slipped into receiver located in the compressor pumpend.Pressure Transducers - TWO tvpes of pressure trans-ducers are used on 30G Flotronic’” Ii*chille&: a low pres-sure transducer and a high pressure transducer. The lowpressure transducer is identified by a white dot on the bodyof the transducer, and the high pressure transducer by a reddot. See Fig. 16.Three pressure transducers are mounted on each lead com-pressor: 2 low-pressure transducers to monitor compressorsuction pressure and oil pressure, and a high-pressure trans-ducer to monitor compressor discharge pressure (seeFig. 17 for exact locations on compressor). Each transduceris supplied with 5 vdc power from a rectifier which changes24 vat to 5 vdc.TROUBLESHOOTING - If transducer is suspected of be-ing faulty, first check supply voltage to transducer. Supplyvoltage should be 5 vdc + .2 v. If supply voltage is cor-rect, compare pressure reading displayed on keypad and dis-play module against pressure shown on a calibrated pres-sure gage. If the 2 pressure readings are not reasonably close,replace pressure transducer.TRANSDUCER REPLACEMENTTransducers are installed directly in the refrigerant cir-rcuit. Relieve all refrigerant pressure using standard re-frigeration practices before removing.1. Relieve refrigerant pressure using standard refrigerationpractices.2. Disconnect transducer wiring at transducer by pullingup on locking tab while pulling weather-tight connectionpfug from end of transducer. Do not pull on trans-ducer wires.3. Unscrew transducer from !&in. male flare fitting. Wheninstalling new pressure transducer, do not use threadsealer. Thread sealer can plug transducer and render itinoperative.4. Insert weathertight wiring plug into end of transduceruntil locking tab snaps in place.5. Check for refrigerant leaks.-75”l/4” SAE FEMALE FLAREWHITE DOT-LOW PRESSURE TRANSDUCERRED DOT -HIGH PRESSURE TRANSDUCERSAE - S o c i e t y o f A u t o m o t i v e E n g i n e e r sFig. 16 - Pressure Transducer60