DEALER SERVICE BULLETIN

Transcription

1 DEALER SERVICE BULLETIN Number: DSB Issued: 10/25/2013 Title: Schrader Valve Core Removal on Humidi-Mizer SRT Units PRODUCT CATEGORY: SRT with Humidi-Mizer System MODELS AFFECTED: Carrier: 48/50 TC04, 05, 06, 07 Serial Number(s): 3511C77243 to 3613C99999 SITUATION: Several small rooftop units with the optional Humidi-Mizer system have been found to contain a Schrader valve core in the equalizer line for the reheat TXV. On small rooftop, electro-mechanical units, there is a connection between the reheat coil TXV equalizer line and the compressor suction line where the equalizer line flare nut screws on a ¼ inch Schrader valve port of the suction line. This flare nut does not have a Schrader depressor, so the ¼ inch Schrader valve port should not have a core installed. During production, the Schrader valve core may have been installed in the port under thetxv equalizer line. This may cause inadequate dehumidification during the reheat mode. When this occurs, there may be a noticeable frosting of the evaporator coil. SOLUTION: Verify proper operation of the reheat TXV (attached is the Unit Start-up Checklist for Humidi-Mizer systems). To prevent this potential restriction of the equalizer line, the Schrader core must be removed from the Schrader valve port under the TXV equalizer flare nut. For units in the field, the Schrader core must be removed. Follow the steps below for field instructions: 1. Perform unit lockout/tagout. 2. Evacuate the refrigerant charge. 3. Unscrew the TXV equalizer line flare nut and inspect for a Schrader core. 4. Using a core removal tool, remove the Schrader core. 6. Screw the equalizer line flare nut back on to the ¼ port without a core. 7. Perform proper charging procedures. 8. Restore power and verify proper operation.

2 DSB Field Action: Verify proper operation of the reheat TXV (attached is the Unit Start-up Checklist for Humidi-Mizer systems). If a core is found, correct units per instructions above. Attachment: Humidi-Mizer Unit Start-up Checklist. Warning: Do not perform any of the servicing instructions provided in this Service Bulletin unless you are a trained and qualified technician. Observe all precautions in the instructions, equipment tags, labels, and observe all other safety precautions that may apply. Failure to follow this warning could result in property damage, personal injury or death.

3 DSB UNIT START-UP CHECKLIST MODEL NO: SERIAL NO: I. PRE_START-UP: VERIFY THAT ALL PACKING MATERIALS HAVE BEEN REMOVED FROM UNIT VERIFY INSTALLATION OF OUTDOOR AIR HOOD VERIFY INSTALLATION OF FLUE EXHAUST AND INLET HOOD VERIFY THAT CONDENSATE CONNECTIONS IS INSTALLED PER INSTRUCTIONS VERIFY THAT ALL ELECTRICAL CONNECTIONS AND TERMINALS ARE TIGHT VERIFY GAS PRESSURE TO UNIT GAS VALVE IS WITHIN SPECIFIED RANGE CHECK GAS PIPING FOR LEAKS CHECK THAT INDOOR-AIR FILTERS ARE CLEAN AND IN PLACE CHECK THAT OUTDOOR AIR INLET SCREENS ARE IN PLACE VERIFY THAT UNIT IS LEVEL CHECK FAN WHEEL AND PROPELLER FOR LOCATION IN HOUSING/ORIFICE, AND VERIFY SETSCREW IS TIGHT VERIFY THAT FAN SHEAVES ARE ALIGNED AND BELTS ARE PROPERLY TENSIONED VERIFY THAT SCROLL COMPRESSORS ARE ROTATING IN THE CORRECT DIRECTION VERIFY INSTALLATION OF THERMOSTAT VERIFY THAT CRANKCASE HEATERS HAVE BEEN ENERGIZED FOR 24 HOURS. II. START-UP CHECK AND VERIFY ALL THAT APPLY: ELECTRICAL SUPPLY VOLTAGE L1-L2 L2-L3 L3-L1 COMPRESSOR AMPS 1. L1 L2 L3 COMPRESSOR AMPS 2. L1 L2 L3 SUPPLY FAN AMPS L1 L2 L3 TEMPERATURES OUTDOOR-AIR TEMPERATURE F DB (DRY BULB) RETURN-AIR TEMPERATURE F DB F WB(WET BULB) COOLING SUPPLY AIR TEMPERATURE F GAS HEAT SUPPLY AIR F PRESSURES GAS INLET PRESSURE IN. WG GAS MANIFOLD PRESSURE STAGE1 IN. WG STAGE2 IN. WG REFRIGERANT SUCTION CIRCUIT A PSIG CIRCUIT B PSIG

4 DSB REFRIGERANT DISCHARGE CIRCUIT A PSIG CIRCUIT B PSIG VERIFY REFRIGERANT CHARGE USING CHARGING CHARTS GENERAL ECONOMIZER MINIMUM VENT AND CHANGEOVER SETTINGS TO JOB REQUIREMENTS WITH ECONOMIZIER / FA CLOSED: RETURN AIR STATIC PRESSURE SUPPLY AIR STATIC PRESSURE IN. WC IN. WC BLOWER WHEEL RPM RPM VERIFY SMOKE DETECTOR PROVIDES UNIT SHUTDOWN UTILIZING MAGNET TEST IV.UNITS WITH HUMIDIMIZER START-UP STEP 1. CHECK CTB FOR JUMPER 5, 6, 7 JUMPER 5, 6, 7 MUST BE CUT AND OPEN 2. OPEN HUMIDISTAT CONTACTS 3. START UNIT IN COOLING (CLOSE Y1) OBSERVE AND RECODE A SUCTION PRESSURE PSIG B DISCHARGE PRESSURE PSIG C ENTERING AIR TEMPERATURE F D LIQUID LINE TEMPERATURE AT OUTLET OF REHEAT COIL F E CONFIRM CORRECT ROTATION FOR COMPRESSOR CHECK FOR CORRECT RAMP-UP OF OUTDOOR FAN MOTOR AS CONDENSER COIL F WARMS 4. CHECK UNIT CHARGE PER CHARGING CHART JUMPER 32LT MOTOR MASTER TEMPERATURE SENSOR DURING THIS CHECK. REMOVE JUMPER WHEN COMPLETE 5. SWITCH UNIT TO HIGH-LATENT MODE (SUBCOOLER) BY CLOSING HUMIDISTAT WITH Y1 CLOSED OBSERVE A. REDUCTION IN SUCTION PRESSURE (5 TO 7 PSI EXPECTED) B. DISCHARGE PRESSURE UNCHANGED C. LIQUID TEMPERATURE DROPS TO 50 TO 55 F RANGE D. LSV SOLENOID ENERGIZED (VALVE CLOSES) 6. SWITCH UNIT TO DEHUMID (REHEAT) BY OPENING Y1 A. SUCTION PRESSURE INCREASES TO NORMAL COOLING LEVEL B. DISCHARGE PRESSURE DECREASES (35 TO 50 PSI) (LIMITED BY MOTORMASTER) C. LIQUID TEMPERTURE RETURNS TO NORMAL COOLING LEVEL

5 DSB D. LSV SOLENOID ENERGIZED (VALVE CLOSES) E. DSV SOLENOID ENERGIZED, VALVE OPENS 7. WITH UNIT IN DEHUMID MODE CLOSE W1 COMPRESSOR AND OUTDOOR FAN STOP LSV AND DSV SOLENOIDS DE-ENERGIZED 8. OPEN W1 RESTORE UNIT TO DEHUMID MODE 9. OPEN HUMIDISTAT INPUT COMPRESSOR AND OUTDOOR FAN STOP LSV AND DSV SOLENOIDS DE-ENERGIZED 10. RESTORE SETPOINTS FOR THERMOSTAT AND HUMIDISTAT