AYK 550 Air-Modulator Engineering Guide

1 AYK 550 Air-ModulatorFORM (704)1 - 75HP208 - - 150HP380 - 480 VACENGINEERING GUIDEYORK INTERNATIONAL2 Nomenclature .. 3 Introduction .. 3 AYK 550 Air-Modulator .. 3 Why Variable Speed? .. 3 What is a Variable Speed Drive? .. 3 Application .. 4 General Application Considerations .. 4 Fan Applications .. 5 Retrofit Fan Applications .. 6 Pump 7 Pump and Fan Control .. 8 Cooling Tower 9 Dimensions .. 10 AYK 550 Frame Size Chart .. 10 Base drive with Conduit Box - Option OO .. 11 Base Drive with Fused Disconnect - Option AO .. 12 Base Drive with 2 Contactor Bypass, Option CM .. 13 Enclosures for Option CM .. 14 Performance Data .. 15200 - 240 Volts .. 15380 - 480 Volts .. 17 Derating Charts .. 19 Top 10 Selling Features .. 20 YORK Package Configurations .. 21CM Package with 2 Contactor Bypass Internal View .. 22 Accessories and Options.

2 26 Guide 35 Appendix A - Wiring Diagrams .. A1 Appendix B - Wiring Sizes .. B1 Table of ContentsFORM INTERNATIONALI ntroductionAir-ModulatorYORK has led the HVAC industry in variable speed drive(VSD) technology since 1979 with the introduction ofthe Turbo- modulator the variable speed drivespecifically designed for centrifugal chiller YORK involvement in applying electronics to HVAC technology exceeds that of any other company eitherin the HVAC industry or the electronics industry. Since1983, when the Air-Modulator was introduced, YORKhas successfully applied thousands of these drives tofans, pumps, and cooling towers providing exceptionalenergy savings, high-reliability, and Air-Modulator Guide is intended as a reference toapplication and installation information for the HVAC design engineer. The content of this Guide providesgeneral theory of operation, application information, keydesign parameters, and complete Variable Speed?

3 Centrifugal fans and pumps are commonly used in HVAC equipment. Because of their centrifugal design, any re-duction in the speed at which the fan or pump operatescauses a cubic reduction in the horsepower the motorrequires. This is represented by the following equation:This shows that a 10% reduction in the RPM of the fanor pump results in a 27% reduction in horsepower re-quired. Therefore, a means by which the RPM or speedof the fan or pump could be reduced would producesignificant energy savings. The Air-Modulator providessuch a means by varying the speed of the fan or is a Variable Speed Drive?A variable speed drive is an electronic device whichchanges the speed of a motor by changing the fre-quency and voltage fed to the motor. An AC motor runsat a speed proportional to the frequency applied, asdescribed in the following formula:The speed is dependent on the frequency; a change infrequency will change the motor speed.

4 The AC motor,however, must also have the voltage vary in the sameproportion as the frequency to maintain full torque ca-pabilities throughout the speed range. Therefore, a vari-able speed drive must change both the frequency andthe voltage of the power fed to the motor to vary speedwhile maintaining torque for the required x frequencyNumber of motor polesSynchronous motor speed =EXAMPLE:SPEED %HP %100%100%90%73%80%51%70%34%60%22%50%13%4 0%7%30%3%_____(RPM2)3 (HP2)(RPM1)3= (HP1)0204060801001200 102030405060708090100 Outlet DamperInlet VanesHydraulic PitchAC DriveFan shaft pow erPowerconsumptionin % of therated fan shaft powerAir Flow in % of the Rated FlowFan Power with Different Air Volume Control MethodsYORK INTERNATIONAL4 ApplicationGENERAL APPLICATION CONSIDERATIONSH orsepower RangeThe YORK Air-Modulator is a complete product linecovering the nominal horsepower sizes from 1 HP to150 HP for 380 to 480V/3-Phase, and 1 HP to 75 HPfor 208V to 240V/3-Phase.

5 This one product line canbe used for the smallest return fan or the largest chilledwater pump. The critical sizing parameter is the outputcurrent rating of the drive (listed on pages 15-17). Thenameplate FLA rating of the motor(s) should not exceedthe output current rating of the drive at 208, 230, 380,or are designed with sufficient currentcapacity to be applied to high efficiency motors. Thecurrent capacity complies with the industry s EnergyPolicy Act (EPACT) motor full load amp ratings. Air-ModFLA output ratings meet or exceed Table 430-150 of theNational Electric Code SupplyThe Air-Modulator is designed for nominal 380V to 480V(+10%), 48-63 Hz input power, or 208V to 240V (-15%),48-63 Hz. For other power supply systems, a steptransformer should be used. The minimum requiredkVA rating of the transformer must be calculated asfollows:Power factor correction capacitors are not required asthe Air-Modulator maintains a.

6 98 power factor atnominal are designed for indoor location, in aNEMA-1 classification area, having 5 F to 104 F(-15 C - 40 C) ambient temperature limits. The relativehumidity of the area should be between 0% to 90% clearance (as noted in the dimensionalsection) to permit normal servicing and maintenanceshould be provided around the entire WiringThe Air-Modulator is equipped with power lugs for easyconnection of power wiring. Maximum wiring size foreach Air-Modulator is listed in the power and controlwiring drawing, Form A single pointground connection is provided in the wiring should be sized and installed in accordancewith the National Electrical Code ( ). Copper wireis required for all power wiring connections to the NOT USE ALUMINUM WIREAir-Mod Terminals Are Not Rated For Use With Aluminum WireFor wiring and fuse sizing purposes, follow the guidelinesfor Rated Input Current and Max Prefuse Amps listed inPerformance Air-Modulator is designed with electronic I2t overload protection which limits the current to100% of the motor rated current eliminating the needfor thermal overload relays.

7 This is in compliance withsection 430-2 of the Wiring / InterfaceYORK provides as standard on Air-Modulators a singlepoint control interface which accepts standard controlsignals (4-20mA, 0-5 VDC, 0-10 VDC) mounted in theunit. Also available for factory mounting is a pneumaticcontrol interface which accepts a standard 3-15 PSIG control :For 380V, 50Hz applications, size VFDfor FLA that meet or exceed motor x 3 x Vs x FLA @ Vs1000 Transformer kVA = Vs = Supply VoltageFORM INTERNATIONALT heory of OperationVariable Air-Volume (VAV) systems have long been ac-cepted as the energy efficient air distribution and other HVAC suppliers have, traditionally, of-fered Variable Inlet Vanes (VIV) on air handling units toprovide this variable air volume capability. VIVs unloadthe fan by adding a pre-swirl to the air as it enters thefan in such a way as to provide a reduction in headpressure across the fan and a decrease in air flow causes a change in the operating point of the fanon the system curve (Fig.)

8 1) and a subsequent reduc-tion in the horsepower drawn by the fan , the Air-Modulator unloads the fan by slow-ing it down. This shifts the RPM curve on which the fanoperates. By reducing the RPM curve, the operatingpoint now requires significantly less brake horsepowerthan a system using VIVs. This is shown in Fig. 2. Thepart load performance comparison is shown in Fig. speed drives can be applied to forward-curved,airfoil or backward-inclined centrifugal fans. When ret-rofitting the Air-Modulator to a fan with existing VIVs,the VIVs should either be removed or locked into theFAN APPLICATIONS wide open position. Leaving the vanes on the fan willrequire the fan to use more power than if they wereremoved. The power penalty can range from 5% to 25%of FLA depending on fan size and velocity of air acrossthe vanes. The smaller the fan, the higher the of OperationThe typical variable speed air system is depicted in It consists of an air handling unit being controlled byan Air-Modulator , ductwork, and standard temperaturecontrols.

9 Under full load conditions, the fan is runningat full speed and the discharge dampers are fully open,allowing the maximum amount of cooling into the the cooling diminishes, the temperature controls senda signal to the dampers to close; this increases the staticpressure in the ductwork. A static pressure sensor inthe ductwork sends a signal through a receiver/control-ler to the Air-Modulator , telling it to slow down the reduced motor and fan speed matches the air flowto the space temperature. As the space temperaturerises, the dampers open lowering the duct static pres-sure. A reduction in static pressure will cause the Air-Modulator to increase the speed of the motor, againmatching the air flow to the space 1 FAN CURVES WITH INLET VANE CONTROLFIG. 2 FAN CURVES WITH VARIABLE SPEED CONTROLLD00893LD00894 Application(continued)HeatingFilterCooli ngOutside airExhaust airReturn fanSupply fan4 - 20 mALineROOM 1 ROOM 2 ROOM 3 ROOM 4 RecirculationDamperPPP4 - 20 mA'PVAV Variable Speed Fans - Control0204060801001200 102030405060708090100 Outlet DamperInlet VanesHydraulic PitchAC DriveFan shaft powerPowerconsumptionin % of therated fan shaft powerAir Flow in % of the Rated FlowFan Power with Different Air Volume Control MethodsFIG.

10 3 AIR-MOD PART LOAD PERFORMANCEFIG. 4 TYPICAL VAV SYSTEMYORK INTERNATIONAL6 RETROFIT FAN APPLICATIONSM echanical Volume Control RetrofitThe Air-Modulator can be easily retrofitted into existingsystems. The exisiting starter controls can be integratedinto the Air-Modulator as well as the existing transducercan be fed into the Air-Mod s PI controller for set-pointcontrol. The existing volum controls (ie: inlet Guide vane,discharge damper, etc) can be removed or locked inthe full open position. See Fig Volume RetrofitThe simplest of all air conditioning systems is a supplyfan unit serving a single zone with constant air volumeas shown in Typically, this system is controlledby a automatic temperature control (ATC) panel thatcycles the AHU starter ON/OFF based on a temperatureof a single zone. This is very inefficient and can beconverted to variable volume with an air modulator whichmonitors room temperature and discharge temperatureto automatically control fan speed by adjusting thefrequency output to the Expansion VAV SystemAir-Modulators can also be used on DX systems.