Carrier FLOTRONIC II 30GN040-420 Operating And Troubleshooting Manual

reading correctly. Connect a calibrated gage to leadcompressor suction or discharge pressure connectionto check transducer reading.e. Make sure transducer leads are properly connected injunction box and at processor board. Check trans-former 5 output. Check voltage transducer 5 vdc6 .2 v.When above checks have been completed, check ac-tual operation of EXV by using procedures outlined inthis step.6. Check operation of EXV.a. Close liquid line service valve of circuit to be checked,and run through the test step ( ) for lead com-pressor in that circuit to pump down low side of sys-tem. Repeat test step 3 times to ensure all refrigeranthas been pumped from low side.NOTE: Be sure to allow compressors to run for thefull pumpout period.b. Turn off compressor circuit breaker(s). Close com-pressor discharge service valves and remove any re-maining refrigerant from low side of system.c. Remove screws holding top cover of EXV. Carefullyremove top cover. If EXV plug was disconnected dur-ing this process, reconnect it after cover is removed.When removing top cover, be careful to avoid dam-aging motor leads.d. Enter appropriate EXV test step for EXVA orEXVB in the outputs subfunction of the test function( ). Press to initiate test. Withcover lifted off EXV valve body, observe operation ofvalve motor and lead screw. The motor should turncounterclockwise, and the lead screw should move upout of motor hub until valve is fully open. Lead screwmovement should be smooth and uniform fromfully closed to fully open position. Press tocheck open to closed operation.If valve is properly connected to processor and receiv-ing correct signals, yet does not operate as describedabove, valve should be replaced.Operation of EXV valve can also be checked withoutremoving top cover. This method depends on opera-tor’s skill in determining whether or not valve is mov-ing. To use this method, initiate EXV test and openvalve. Immediately grasp EXV valve body. As valvedrives open, a soft, smooth pulse is felt for approxi-mately 26 seconds as valve travels from fully closedto fully open. When valve reaches end of its openingstroke, a hard pulse is felt momentarily. Drive valveclosed and a soft, smooth pulse is felt for the 52 sec-onds necessary for valve to travel from fully open tofully closed. When valve reaches end of its stroke, ahard pulse is again felt as valve overdrives by 50 steps.Valve should be driven through at least 2 complete cyclesto be sure it is operating properly. If a hard pulse isfelt for the 26-second duration, valve is not movingand should be replaced.The EXV test can be repeated as required by enter-ing any percentage from 0 ( ) to 100 to initiatemovement.If operating problems persist after reassembly, they maybe due to out-of-calibration thermistor(s) or intermittentconnections between processor board terminals and EXVplug. Recheck all wiring connections and voltage signals.Other possible causes of improper refrigerant flow con-trol could be restrictions in liquid line. Check for pluggedfilter drier(s) or restricted metering slots in the EXV. For-mation of ice or frost on lower body of electronic ex-pansion valve is one symptom of restricted metering slots.However, frost or ice formation is normally expected whenleaving fluid temperature from the cooler is below 40 F.Clean or replace valve if necessary.NOTE: Frosting of valve is normal during compressortest steps and at initial start-up. Frost should dissipate af-ter 5 to 10 minutes operation in a system that is operatingproperly. If valve is to be replaced, wrap valve with a wetcloth to prevent excessive heat from damaging internalcomponents.Thermostatic Expansion Valve (TXV) — Refer tobase unit Installation Instructions for TXV information(30GN040,045 with optional brine only).Thermistors — All thermistors are identical in their tem-perature vs. resistance performance. Resistance at various tem-peratures are listed in Tables 17 and 18.LOCATION — General location of thermistor sensors areshown in Fig. 14.Cooler Leaving Fluid Thermistor (T1) — T1 is located inleaving fluid nozzle. The probe is immersed directly in thefluid. All thermistor connections are made through a 1⁄4 -in.coupling. See Fig. 16. Actual location is shown in Fig. 14and 15.Cooler Entering Fluid Thermistor (T2) — T2 is located incooler shell in first baffle space near tube bundle. Thermistorconnection is made through a 1⁄4 -in. coupling. See Fig. 16.Actual location is shown in Fig. 14 and 15.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. See Fig. 14and 15.THERMISTOR REPLACEMENT (T1, T2, T7, T8)Thermistors are installed directly in fluid Relieve all pres-sure using standard practices or drain fluid before re-moving.Proceed as follows (see Fig. 16):To replace thermistor sensor T2:1. Remove and discard original thermistor and coupling.IMPORTANT: Do not disassemble new coupling.Install as received.2. Apply pipe sealant to 1⁄ 4-in. NPT threads on replacementcoupling and install in place of original. Do not use pack-ing nut to tighten coupling. This damages ferrules (seeFig. 16).3. Insert new thermistor in coupling body to its full depth.If thermistor bottoms out before full depth is reached, pullthermistor back out 1⁄8 in. before tightening packing nut.Hand tighten packing nut to position ferrules, then finishtightening 1 1⁄4 turns with a suitable tool. Ferrules are nowattached to thermistor which can be withdrawn from cou-pling for unit servicing.To replace thermistors T1, T7, and T8:Add a small amount of thermal conductive grease to ther-mistor well. Thermistors are friction-fit thermistors, whichmust be slipped into well located in the compressor pumpend.57