Carrier 30HXC Series Installation, Operation And Maintenance Instructions

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Carrier 30HXC Series Installation, Operation And Maintenance Instructions Manual pdf 26 page image

2614 - MAJOR SYSTEM COMPONENTS ANDOPERATION DATA14.1 - Geared twin screw compressor• 30HXC and 30GX units use 06N geared twin screwcompressors• 06NA are used on 30GX (air-cooled condensing application)• 06NW are used on 30HXC (water-cooled condensingapplication)• Nominal capacities range from 39 to 80 tons. Economized ornon economized models are used depending on the 30HXCand 30GX unit size.14.1.1 - Oil FilterThe 06N screw compressor has an oil filter integral in thecompressor housing. This filter is field replaceable.14.1.2. - RefrigerantThe 06N screw compressor is specially designed to be used inR134 a system only.14.1.3 - LubricantThe 06N screw compressor is approved for use with thefollowing lubrifiant.CARRIER MATERIAL SPEC PP 47-3214.1.4 - Oil Supply Solenoid ValveAn oil supply solenoid valve is standard on the compressor toisolate the compressor from oil flow when the compressor isnot operating.The oil solenoid is field replaceable.14.1.5 - Suction & Economizer ScreensTo increase the reliability of the compressor, a screen has beenincorporated as a standard feature into suction and economizerinlets of the compressor.14.1.6 - Unloading SystemThe 06N screw compressor has an unloading system that isstandard on all compressors. This unloading system consists oftwo steps of unloading that decrease the compressor capacityby rerouting partially compressed gas back to suction.14.2 - Evaporator30HXC and 30GX chillers use a flooded evaporator. The watercirculates in the tubes and the refrigerant is on the outside inthe shell. One vessel is used to serve both refrigerant circuits.There is a center tube sheet which separates the two refrigerantcircuits. The tubes are 3/4" diameter copper with an enhancedsurface inside and out. There is just one water circuit, anddepending on the size of the chiller, there may be two or threewater passes. A cooler liquid level sensor provides optimizedflow control.At the top of the cooler are the two suction pipes, one in eachcircuit. Each has a flange welded to it, and the compressormounts on the flange.14.3 - Condenser and oil separator (30HXC)30HXC chiller use a vessel that is a combination condenserand oil separator. It is mounted below the cooler. Discharge gasleaves the compressor and flows through an external muffler tothe oil separator, which is the upper portion of the vessel. Itenters the top of the separator where oil is removed, and thenflows to the bottom portion of the vessel, where gas iscondensed and subcooled. One vessel is used to serve bothrefrigerant circuits. There is a center tube sheet which separatesthe two refrigerant circuits. The tubes are 3/4" or 1" diametercopper with enhanced surface inside and out. There is just onewater circuit with two water passes.14.4 - Oil separator (30GX)In the air-cooled units, the oil separator is a pressure vessel thatis mounted under the outside vertical condenser coils.Discharge gas enters at the top of the separator where much ofthe oil separates and drains to the bottom. The gas then flowsthrough a wire mesh screen where the remaining oil isseparated and drains to the bottom.14.5 - Electronic Expansion Device (EXD)The microprocessor controls the EXD through the EXV controlmodule. The EXD will either be an EXV or an Economizer.Inside both these devices is a linear actuator stepper motor.High-pressure liquid refrigerant enters the valve through thebottom. A series of calibrated slots are located inside the orificeassembly. As refrigerant passes through the orifice, the pres-sure drops and the refrigerant changes to a 2-phase condition(liquid and vapor). To control refrigerant flow for differentoperating conditions, the sleeve moves up and down over theorifice, thereby changing effective flow area of expansiondevice. The sleeve is moved by a linear stepper motor. Thestepper motor moves in increments and is controlled directlyby the processor module. As the stepper motor rotates, motionis transferred into linear movement by the lead screw. Throughthe stepper motor and lead screws, 1500 discrete steps ofmotion are obtained. The large number of steps and long strokeresult in very accurate control of refrigerant flow. Each circuithas a liquid level sensor mounted vertically into the top of thecooler shell. The level sensor consists of a small electricresistance heater and three thermistors wired in seriespositioned at different heights inside the body of the well. Theheater is designed so that the thermistors will readapproximately 93.3°C in dry air. As the refrigerant level risesin the cooler, the resistance of the closest thermistor(s) willgreatly change. This large resistance difference allows thecontrol to accurately maintain a specified level. The levelsensor monitors the refrigerant liquid level in the cooler andsends this information to the PSIO-1. At initial start-up, theEXV position is at zero. After that, the microprocessor keepsaccurate track of the valve position in order to use this infor-mation as input for the other control functions. It does this byinitializing the EXV’s at startup. The processor sends outenough closing pulses to the valve to move it from fully opento fully closed, then resets the position counter to zero. Fromthis point on, until the initialization, the processor counts thetotal number of open and closed steps it has sent to each valve.14.6 - EconomizerEconomizers are installed on 30HXC 190, 285 and 375 and30GX 182, 267 and 358.The economizer improves both the chiller capacity andefficiency as well as providing compressor motor cooling.Inside the economizer are both a linear EXV stepper motor anda float valve. The EXV is controlled by the PIC to maintain the