RTWA 108-110 - Trane

1 RT WA 108-110 Screw compressor liquid chiller, circuit Packaged unit. Nominal cooling capacity : 130 to 180 kW (R134a, 50 Hz). Trane Helirotor screw compressor. Microprocessor based stepless capacity control. Adaptive Control providing superior operation reliability. Easy integration in a Building Management System. Electronic expansion valve. Factor y tested prior to shipment. Designed and manufactured in accordance with the TRANEQ uality Management System, approved to ISO Screw compressor liquid chiller, water cooling capacities : 130 to 180 kW (R134a, 50Hz).By introducing the RTWA, Trane is now ableto offer a complete range of liquid chillers fittedwith rotary compressors covering the coolingcapacity range from 50 up to 4000 the largest cooling capacities, Trane offersthe centrifugal compressor liquid chillers.

2 Thesemachines have an excellent reputation for relia-bility . A survey published in the USA in 1988revealed that more than 90% of the centrifugalchillers installed during the 50 last years werestill in lower cooling capacities, Trane has intro-duced more recently, the 3D-Scroll compressorsand the Helirotor Screw these technologies still being conside-red a novelty in some quarters, within Trane this relates to todays technology : for examplethe 3D-Scroll compressors introduced in 1989have completely replaced the reciprocating com-pressors for cooling capacities up to 160 the upper range, thewater-cooled Screwcompressor liquidchillers, seriesRTHA, introducedin 1988.

3 Is a verysuccesful product: with more than1500 machinesinstalled everyyear worlwide, Trane can beconsidered asthe Number 1 inthis area. Trane has also introduced a range ofair cooled Screw compressor liquid the type of technology, the rotarycompressors offer some very specific commonbenefits : superior energy efficiency and reliabili-ty combined with reduced sound and vibrationlevel being the most obvious : Number 1 in rotar y compressors : A combination of the latest technological innova-tions in the field of liquid RTWA offers in many areas a combinationof the most advanced technologies availabletoday :- Screw compressor, with stepless capacitycontrol and 5/7 lobes rotors profiles desi-gned and patented by Advanced microprocessor based "Adaptive Control" including PID leavingchilled water temperature control and aserial communication link for easy integra-tion into a Building Management Electronic expansion valve.

4 Gives steadieroperation, optimized evaporator efficiencyand improved energy efficiency with reducedcondensing High efficiency heat exchange surfaces :energy efficiency combined with reducedsurface the specifier :- High energy efficiency, less floor spacerequired : the unit can be more easilyintegrated into an existing plant room,which allows for an increase of the avai-lable cooling Higher application flexibility : ice stora-ge, multiple operating conditions- Reduced sound and vibrations levelsallowing installation in sensitive the mechanical contractor :- Compact design, reduced shippingweight : easier handling during Condenser hydraulic connections pos-sible from both sides allowing easierintegration into the plant Fully factory tested reducing the com-missioning cost and the operating contractor :- State of the art motor protection : theunit control module permanentlysenses the current of each phase of themotor power supply as well as the tem-perature of the motor windings, thusensuring a complete and efficient pro-tection of the Adaptive Control, anticipates any ope-rating problems.

5 The control moduleconsequently takes corective actions toenable the chiller to stay within opera-ting limits to guarantee trouble freeoperation even under critical condi-tions. The unit control module is pro-grammed to react when faced with anemergency situtation such as refrige-rant loss, too low evaporator water flowrate, phase imbalance or even a stuckcontactor. The chiller can continue tooperate at a reduced load under thesecritical conditions until normal opera-tion can be restored whereas a stan-dard chiller would just stop as a Sophisticated operator interface : theclear language display board allows fora quick and precise identification of theoperating status of the machine or of anoperating fault as soon as it is detectedby the unit control Serial link allows for a remote monito-ring of the the owner :- Superior energy efficiency reducingoperating Increase chiller life and drasticallyreduced maintenance costs.

6 The com-pressors have been designed to opera-te for the whole life of the chillerwithout any major maintenance opera-tions. - Steady and safe operation : thanks tothe stepless capacity control, the elec-tronic expansion valve and the sophisti-cated control algorithms, the chillercan exactly match the required coolingcapacity and maintain the chiller wateroutlet temperature within a range of + C of the Serial communication link facility tostart and stop the chiller, modify thesetpoints or to limit the current drawnfrom a remote : Designed to offer more attractive benefits in all American Standard Inc. 20003 Trane Helirotor Screw compressors :Superior energy efficiency and expansion valve-Less critical components : only two rotatingparts, reduced number of components and par-ticularly of critical parts (the total number ofcritical components is on average 30 timeslower compared to a standard reciprocatingchiller)-Rugged design : all potentially fragile compo-nents (suction and discharge valves, springs)have been eliminated,the compressors are fit-ted with class 5 bearings designed not to bereplaced during compressor life time.

7 Thisperformance cannot be compared with recipro-cating compressors and even existing screwcompressors which are fitted with journal bea-rings which require periodical overhauling tocheck or replace the rotor 5/7 lobes profiles patentedby Trane : only Trane provide this specificcompressor design. This specific design gua-rantees a superior rotor rigidity. The latest evo-lutions allow in particular an extended capacitycontrol range precision machining : the very preciserotor tip tolerance (10 micrometers) is achie-ved due to the most advanced machine toolsavailable today. Trane is ableto build screw compressorswith a reduced amount ofleakage between thehigh and low pressurecavities.

8 As a result, theenergy efficiency of thecompressor is conside-rably improved comparedto the first generation of screwcompressors which were in some cases derived from air compression technolgy- Rotary compressor :reduced sound andvibration level compared to reciprocatingequipments. The overall sound level is lowerand furthermore the shape ofthe soundspectrum isdifferent : the soundlevel is inferior in the low frequenciesbands. The noise generated is not onlyless troublesome but also easier to coupled with Trane Adaptive Controlmicroprocessor, the electronic expansion valvesignificantly improves part load performance ofthe RTWA chiller by minimizing superheat inthe evaporator and allowing the chiller to run atreduced condensing which use conventional TXV must runat higher head pressures and consume morepower at part load than the electronic expansion valve andits control allow much better control over dyna-mic load and head changes.

9 Under these condi-tions a conventional TXV may never achievecontrol stability and "huntings" and liquid slug-ging are refrigerant flow meteringThe electronic expansion valve is actuated by astepper motor. The exact valve position is per-manently known by the Unit Control responseTo operate the valve from fully closed to fullyopen position requires less than 30 is to compare with thermo-electric deviceswhich have no stable position and require up toseveral minutes to fully tightnessBecause of the superior tightness of the electro-nic expansion valve when full closed the liquidline solenoid valve is no more enables to further improve the reliability ofthe chiller by reducing the total number ofmoving 134a.

10 A new non-flammable, non-toxic, chlorine-free refrigerantwith zero ozone depletion 134a is very well suited to replace CFC 12but also HCFC 22 in most liquid chiller applica-tions, in particular for screw compressor comfortcooling and process 134a is listed in the European EINECS-inventory of approved chemical compounds forwhich no further toxicity testing is required bythe voluntary toxicity testing programme whichincludes HFC 134a (PAFT 1), a cooperative re-search effort of the 15 leading chemicals compa-nies in the world, was undertaken to facilitate andaccelerate the phase out of CFC PAFT programme on HFC 134a is results show that HFC 134a will be at leastas safe as CFC 12 which has an excellent record,including in medical PAFT members have set the recommendedoccupational exposure limit for HFC 134a at1000 ppm, the highest level that is ever assignedto any industrial chemical.