Carrier 17DA Start-up, Operation And Maintenance Instructions Manual

Also see for 17DA: Start-up instructions Application data Operating and maintenance instructions Start-up instructions

14refrigerant side of the seal and the oil supply being controlledby the differential pressure regulator. The pressure being sup-plied to the seal is maintained at 35 psid above the pressure onthe refrigerant side of the shaft seal. The auxiliary oil pumpshould start if the differential pressure falls to or below 23 psid.Lower the oil pressure by adjusting the differential oil pres-sure regulator until the oil pressure drops to 23 psid. On com-pletion of the test, reset the oil pressure regulator to its normalsetting of 35 psid. The auxiliary pump will stop when the oilpressure rises above 27 psid.CHECK SEAL OIL DIFFERENTIAL PRESSURETRANSDUCER — This function shuts down the compressorif the seal oil pressure differential drops below its fault limit.The transducer should be checked for proper calibration bycomparing against a known pressure gage. If two individualsingle input transducers are used instead of a differential trans-ducer, the measured pressures will be compared by the PLC tocalculate the differential pressure reading.CHECK THRUST BEARING OIL PRESSURE TRANS-DUCER — This function shuts down the compressor if thethrust bearing oil pressure drops below its fault limit. The thrustbearing is in the ambient atmosphere so the oil pressure is ref-erenced to ambient pressure. The transducer should be checkedfor proper calibration by comparing against a known pressuregage and the set point should be checked on the PLC screen.CHECK DISCHARGE GAS HIGH-TEMPERATURECUTOUT — This function shuts down the compressor if thecompressor discharge gas temperature exceeds its fault limit.The sensor is located in a temperature well in the back wall ofthe compressor. It is located to the immediate right of the bear-ing chamber on the 7 frame compressor and to the immediateleft of the bearing chamber on the 8 frame compressor. Thesensor should be compared against a calibrated sensor in a cali-bration bath or dry block calibrator.CHECK THRUST BEARING OIL HIGH-TEMPERA-TURE CUTOUT — This function shuts down the compressorif the temperature of the oil leaving the compressor exceeds itsfault limit. The sensor is located in the bearing chamber and isinserted into the leaving oil temperature well that is an integralpart of the thrust bearing housing.The sensor should be compared against a calibrated sensorin a calibration bath or dry block calibrator.CHECK SHAFT MOVEMENT SWITCH — The shaftmovement switch will shut down the compressor if the thrustbearing has been damaged. This protects the impeller fromdamage. The switch is mounted inside the bearing chamber atsplitline level. It is actuated by a trigger screw that protrudesfrom the main shaft.With the shaft in the thrust position, the clearance betweenthe screw head and the switch should be 0.014 to 0.015 in.(0.356 to 0.038 mm) as shown in Fig. 5.Check the integrity of the wiring and connections betweenthis switch and the bulkhead terminals. If this switch hasopened during compressor operation, do not restart the ma-chine. Contact a Carrier service representative immediately.CHECK COOLER AND CONDENSER MINIMUMFLOW PROTECTION — Flow monitoring devices are spec-ified per job, however the common purpose is to prevent dam-age to the chiller due to insufficient water flow. With the chillernot in operation, reduce water flow to each vessel in turn untilthe low flow cutout function activates. Confirm the flow rate iscorrect. Calibrate the monitor(s) as required.CHECK AUXILIARY INTERLOCKS — Refer to the jobwiring drawing for interlock wiring. Interlocks and safety con-trols must deenergize the main holding coil, turbine solenoidtrip, etc. to shut down the refrigeration compressor under un-safe conditions. Serious damage to the machine could result ifsafety devices are bypassed.CHECK CONDENSER SUBCOOLER LEVEL CON-TROL — The purpose of this function is to control the liquidvalve in the condenser drain line. The liquid level in the con-denser shell should be as close as possible to the deck that di-vides the condenser section from the subcooler section. Whenthe level is correct and the chiller is running near design condi-tions, the correct level should result in a temperature reading of0 to 2° F below saturated condensing temperature at the con-densed liquid thermowell near the subcooler inlet.The control consists of a level transmitter with the PLC sup-plying the signal to the liquid valve. A self-contained pneumat-ic or electronic level control may also be supplied which con-trols the liquid valve directly.To calibrate either type of control, initially set the level sothat the sight glass or transmitter output indicates that the levelis approximately at the level of the condensed liquid thermo-well. Make final adjustment based on the condensed liquidtemperature. If the temperature is too low, drop the level. If thetemperature is too high, raise the level.CHECK COMPRESSOR GUIDE VANE CONTROL —The standard guide vane actuator is a pneumatic piston actua-tor controlled by a built-in positioner. The positioner receives a3 to 15 psig signal. The signal comes from an electric-to-pneu-matic transducer controlled by the PLC. The actuator isequipped with a solenoid operated “quick-dump” valve. Thisallows the vanes to immediately close on compressor shut-down and prevents the guide vanes from operating until thechiller is fully in “run” condition. The solenoid is controlled bythe PLC.The maximum guide vane opening should be set in the PLCsuch that the vanes stop opening when the position indicatorbeneath the actuator points to 90.Set the supply air pressure regulator for 80 psig minimum,100 psig maximum. The cushion air supply to the bottom ofthe piston should be set for 40 psig. The cushion air pressuremay be varied to suit job conditions. Cushion air pressure clos-es the guide vanes. If an adjustment is made it must be proventhat the vanes can readily close before the compressor is start-ed. Increasing cushion air pressure slows the vane openingspeed and increases the vane closing speed. Ensure that the airsupply is filtered and dry.CHECK OIL PRESSURE REGULATORS — Maintain bymaking proper adjustments and providing clean and ample oilsupply. See Oil Cycle section on page 18 for more information.Thrust Bearing Oil Pressure Regulator — The regulator re-duces the main oil pump discharge pressure to 18 psig for driveend journal bearing and thrust bearing lubrication.Differential Back-Pressure Regulator — The regulator main-tains a differential pressure of 35 psid between oil pump dis-charge pressure and pressure in refrigerant side, back-of-sealsection of compressor. Excess oil is relieved directly to oilsump. This control maintains oil supply pressure higher thanFig. 5 — Shaft Movement Switch Detaila17-574