Carrier 30GTN Service And Troubleshooting Manual

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Carrier 30GTN Service And Troubleshooting Manual Manual pdf 47 page image

3. Make sure that thermistor leads are connected to the properpin terminals at the J5 terminal strip on EXV board andthat thermistor probes are located in proper position inthe refrigerant circuit.When these checks have been completed, the actual op-eration of the EXV can be checked by using the proceduresoutlined in Step 5 — Check Operation of the EXV sectionbelow.STEP 5 — CHECK OPERATION OF THE EXV — Use thefollowing procedure to check the actual operation of the EXVs.The ENABLE/OFF/REMOTE contact switch must be in theOFF position.1. Close the liquid line service valve for the circuit to bechecked and run through the appropriate service test topump down the low side of the system. Run lead com-pressor for at least 30 seconds to ensure all refrigeranthas been pumped from the low side and that the EXV hasbeen driven fully open (1500 steps).NOTE: Do not use the Emergency ON-OFF switch to re-cycle the control during this step.2. Turn off the compressor circuit breaker(s) and the controlcircuit power and then turn the Emergency ON/OFF switchto the OFF position. Close compressor service valves andremove any remaining refrigerant from the low side ofthe system.3. Remove screws holding top cover of EXV. Carefully re-move top cover, using caution to avoid damage to the O-ringseal and motor leads. If EXV plug was disconnected dur-ing this process, reconnect it after the cover is removed.4. Note position of lead screw (see Fig. 14). If valve hasresponded properly to processor signals in Step 5.1 above,the valve should be fully open and the lead screw shouldprotrude approximately 1⁄ 4 in. to 3 ⁄4 in. above the top ofthe motor.5. Recycle the control by turning the control circuit poweron and switching the Emergency ON-OFF switch to theON position. This puts the control in initialization mode.During the first 60 seconds of the initialization mode, eachvalve is driven to the fully closed position (1500 steps)by the processor. With the cover lifted off the EXV valvebody, observe the operation of the valve motor and leadscrew. The motor should turn in the counterclockwise (CCW)direction and the lead screw should move down into themotor hub until the valve is fully closed. Lead screw move-ment should be smooth and uniform from the fully opento the fully closed position.6. When test has been completed, carefully reassembleexpansion valve. Be careful not to damage motor orO-ring when reassembling valve. Open compressor serv-ice valves and close compressor circuit breakers. Openliquid line service valve. Turn the ENABLE/OFF/REMOTEcontact switch and allow unit to operate. Verify properoperation of unit.This process of opening and closing the EXV (EXV.A/EXV.B under OUTS) can be repeated by using these ServiceTest steps and recycling the control as described in the pre-ceding steps. If the valve does not operate as described whenproperly connected to the processor and receiving the cor-rect signals, it should be replaced.If operating problems persist after reassembly, they maybe due to out-of-calibration thermistor(s) or intermittent con-nections between the EXV board terminals and the EXV plug.Recheck all wiring connections and voltage signals.Other possible causes of improper refrigerant flow con-trol could be restrictions in the liquid line. Check for pluggedfilter drier(s), restricted metering slots in the EXV, or par-tially closed liquid line service valves. Formation of ice orfrost on the lower body of the EXV is one symptom of re-stricted metering slots. Clean or replace the valve if neces-sary. Wrap a wet cloth around the valve if it is to be replacedto prevent the heat from damaging the internal componentsof the valve.NOTE: Frosting of the valve is normal during service testand at initial start-up. The frost should dissipate after 5 to10 minutes operation of a system that is operating properly.NOTE: The EXV orifice is a screw-in type and may be re-moved for inspection and cleaning. Once the top cover hasbeen removed, the EXV motor may be taken out by remov-ing the 2 cap screws securing motor to valve body. Pull mo-tor, lead screw, and the slide assembly up off the orifice as-sembly. See Fig. 14. A slot has been cut in top of orificeassembly to facilitate removal using a large screwdriver. Turnorifice assembly counterclockwise to remove.When cleaning or reinstalling orifice assembly, be carefulnot to damage orifice assembly seals. The bottom seal actsas a liquid shut-off, replacing a liquid line solenoid valve.Reassembly of valve is made easier by screwing the slideand lead screw assembly out of the motor. Align hole in topof slide with the guide pin in orifice assembly and gentlypush slide and lead screw onto orifice assembly about half-way. Screw motor onto lead screw and secure EXV motorwith cap screws. Be careful not to twist or pull on wires fromEXV motor to valve cover pin connections. Check EXV op-eration in quick step steps.Alarms and Alerts — These are warnings of abnormalor fault conditions, and may cause either one circuit or thewhole unit to shut down. They are assigned code numbers asdescribed in Table 27.47