SDR Single Duct VAV Terminals (FORM 130.13-EG1) - Enviro-Tec

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Single-Duct, VAV Terminals CATALOG: ET130.13-EG1 (1212)STANDARD AND OPTIONAL FEATURESSTANDARD FEATURESConstruction• AHRI 880 certified and labeled• 22 gauge galvanized steel casing and valve• 1/2” thick fiberglass insulation, mechanically fastenedfor added securityPrimary Air Valve• Embossed rigidity rings• Low thermal conductance damper shaft• Position indicator on end of damper shaft• Mechanical stops for open and closed position• FlowStar center averaging airflow sensor• Balancing tees• Plenum-rated sensor tubingHot Water Coil• Designed and manufactured by Johnson Controls• AHRI 410 certified and labeled• 1, 2, 3 or 4 rows• Left or right hand connections• Tested at a minimum of 450 PSIG under water andrated at 300 PSIG working pressure at 200°FElectrical• cETL listed for safety compliance with UL 1996• NEMA 1 wiring enclosureElectric Heat• cETL listed as an assembly for safety compliance• Automatic reset primary and back-up secondarythermal limits• Airflow switch• Single point power connection• Hinged electrical enclosure door• Fusing per NECOPTIONAL FEATURESConstruction• 20 gauge galvanized steel construction• 3/4” and 1” insulation• Foil faced scrim backed insulation• 1/2” thick elastomeric closed cell foam insulation• Double wall construction with 22 gauge linerHot Water Coil• Coil access plate for cleaning coilElectrical• Toggle disconnect switch• Primary and secondary transformer fusingElectric Heat• Proportional SSR heater control• Mercury contactors• Door interlocking disconnect switchesControls• Factory provided controls include:- Analog electronic- PneumaticPiping Packages• Factory assembled – shipped loose for field installation• 1/2” and 3/4”, 2 way, normally closed, two positionelectric motorized valves• Isolation ball valves with memory stop• Fixed and adjustable flow control devices• Unions and P/T ports• Floating point modulating control valves• High pressure close-off actuators8 ENVIRO-TEC
Single-Duct, VAV Terminals CATALOG: ET130.13-EG1 (1212)APPLICATION AND SELECTIONACOUSTICAL CONCEPTSThe focus on indoor air quality is also having an effecton proper selection of air terminal equipment withrespect to acoustics.Sound. At thezone level, theterminal unitgeneratesacousticalenergy that canenter the zonealong two primarypaths.First, soundfrom the primaryair valve can propagate through the downstreamduct and diffusers before entering the zone (referredto as Discharge or Airborne Sound). Acoustical energyis also radiated from the terminal casing and travelsthrough the ceiling cavity and ceiling system beforeentering the zone (referred to as Radiated Sound).To properly quantify the amount of acoustical energyemanating from a terminal unit at a specific operatingcondition (i.e. CFM and static pressure), manufacturersmust measure and publish sound power levels.The units of measurement, decibels, actually representunits of power (watts). The terminal equipment soundpower ratings provide a consistent measure of the generatedsound independent of the environment in whichthe unit is installed. This allows a straight forward comparisonof sound performance between equipmentmanufacturers and unit models.Noise Criteria (NC). The bottom line acoustical criteriafor most projects is the NC (Noise Criteria) level.This NC level is derived from resulting sound pressurelevels in the zone. These sound pressure levels arethe effect of acoustical energy (sound power levels)entering the zone caused by the terminal unit and othersound generating sources (central fan system, officeequipment, environment, etc.).The units of measurement is once again decibels; however,in this case decibels represent units of pressure(Pascals), since the human ear and microphones reactto pressure variations.There is no direct relationship between sound powerlevels and sound pressure levels. Therefore, we mustpredict the resulting sound pressure levels (NC levels)in the zone based in part by the published sound powerlevels of the terminal equipment. The NC levels aretotally dependent on the project specific design, architecturallyand mechanically. For a constant operatingcondition (fixed sound power levels), the resulting NClevel in the zone will vary from one project to another.AHRI 885. A useful tool to aid in predicting space soundpressure levels is an application standard referred toas AHRI Standard 885. This standard provides information(tables, formulas, etc.) required to calculate theattenuation of the ductwork, ceiling cavity, ceiling system,and conditioned space below a terminal unit.These attenuation values are referred to as the “transferfunction” since they are used to transfer from themanufacturer’s sound power levels to the estimatedsound pressure levels resulting in the space below,and/or served by the terminal unit. The standard doesnot provide all of the necessary information to accommodateevery conceivable design; however, it doesprovide enough information to approximate the transferfunction for most applications. Manufacturers usedifferent assumptions with respect to a “typical” projectdesign; therefore, it is impossible to compare productperformance simply by looking at the published NCvalues.GENERAL DESIGN RECOMMEND-ATIONS FOR A QUIET SYSTEMThe AHU. Sound levels in the zone are frequentlyimpacted by central fan discharge noise that eitherbreaks out (radiates) from the ductwork or travelsthrough the distribution ductwork and enters the zoneas airborne (discharge) sound. Achieving acceptablesound levels in the zone begins with a properly designedcentral fan system which delivers relatively quiet air toeach zone.Supply Duct Pressure. The primary factor contributingto noisy systems (including single duct applications)is high static pressure in the primary air duct. Thiscondition causes higher sound levels from the centralfan and also higher sound levels from the terminal unit,as the primary air valve closes to reduce the pressure.This condition is compounded when flexible duct isutilized at the terminal inlet, which allows the centralfan noise and air valve noise to break out into the ceilingcavity and then enter the zone located below theterminal. Ideally, the system static pressure should bereduced to the point where the terminal unit installedon the duct run associated with the highest pressuredrop has the minimum required inlet pressure todeliver the design airflow to the zone. Many of today’sENVIRO-TEC 9
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SDR Single Duct VAV Terminals (FORM 130.13-EG1) - Enviro-Tec

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