Chilled-Water VAV Systems - HVAC.Amickracing

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Primary System ComponentsTable 8. Applications guidelines for various filter typesCollectionefficiency 1IEST Type F( 99.999% on 0.1 to0.2 μm particles)IEST Type D( 99.999% on 0.3 μmparticles)IEST Type C( 99.99% on 0.3 μmparticles)IEST Type A( 99.97% on 0.3 μmparticles)MERV 16MERV 15MERV 14MERV 13MERV 12MERV 11MERV 10MERV 9MERV 8MERV 7MERV 6MERV 5MERV 4MERV 3MERV 2MERV 1Dust-spotefficiencyn/an/an/an/an/a>95%90% to 95%80% to 90%70% to 75%60% to 65%50% to 55%40% to 45%30% to 35%25% to 30%
Primary System ComponentsKey factors to consider when selecting particulate filter types for a specificapplication include:• Target particle size and degree of cleanliness required (collectionefficiency)The “collection efficiency” of a particulate filter is a function of how well itremoves particles of various sizes. Filters with higher efficiencies removea higher percentage of particles, and smaller particles, than filters withlower efficiencies. Since particulate contaminants vary in size (Figure 34),it is important to define the contaminants of concern for a given facilitywhen selecting the type of filter to be used.• Allowable airside pressure dropA direct correlation usually exists between collection efficiency andairside pressure drop. Generally, a filter with a higher efficiency will causea higher pressure drop in the passing air stream, increasing fan energyuse. The number of pleats in a media filter determines the surface area ofthe media. In general, the more surface area, the lower the airsidepressure drop. Pressure drop is also related to air velocity; higher velocitythrough a media filter results in a higher static pressure drop.Figure 36. Angled filters increasesurface area and lower airsidepressure dropOne common method of reducing airside pressure drop is to angle thefilters within the air-handling unit (Figure 36). This decreases air velocitythrough the media and increases the surface area of the media, whichincreases its dirt-holding capacity.• Dirt-holding capacityDirt-holding capacity is an indication of how much dirt the filter will holdat the “dirty” (or final) pressure drop. This indicates how often the filterwill need to be replaced. In general, a filter with more media surface areawill hold more dirt and will need to be replaced less frequently. (Thisvaries with the brand of filter.)• Available spaceIn general, filters with higher efficiencies, lower airside pressure drop,and/or greater dirt-holding capacity, require more space than filters thatperform more poorly in these categories. This can impact the physicalsize of the air-handling unit.• Available budgetFilters with more media surface area generally cost more than filters withless surface area. This impacts both the installed cost and maintenance(replacement) cost of the filter system.In a typical VAV system, the mixture of outdoor air and recirculated return airpasses through a particulate filter to remove airborne particulatecontaminants. Locating these filters upstream of the heating and coolingcoils (Figure 37) helps keep the coils cleaner for a longer period of time, andallows the system to operate more efficiently.SYS-APM008-EN Chilled-Water VAV Systems 43
Page 3 and 4: Chilled-WaterVAV SystemsJohn Murphy
Page 5 and 6: ContentsPreface ...................
Page 8 and 9: VAV terminal units ................
Page 10 and 11: Overview of a Chilled-Water VAV Sys
Page 20 and 21: Primary System Componentsunit are t
Page 22 and 23: Primary System ComponentsAvoiding f
Page 24 and 25: Primary System ComponentsFigure 10.
Page 28 and 29: Primary System Componentsweather, a
Page 32 and 33: Primary System Componentsair to a t
Page 34 and 35: Primary System Componentsbarometric
Page 36 and 37: Primary System ComponentsFigure 20
Page 38 and 39: Primary System ComponentsSupply fan
Page 40 and 41: Primary System ComponentsFan typesV
Page 42 and 43: Primary System ComponentsTo allow a
Page 44 and 45: Primary System ComponentsIn a draw-
Page 46 and 47: Primary System ComponentsSupply fan
Page 48 and 49: Primary System ComponentsThe modula
Page 54 and 55: Primary System Componentssystem. So
Page 56 and 57: Primary System ComponentsPhotocatal
Page 58 and 59: Primary System ComponentsPCO techno
Page 60 and 61: Primary System Componentsand upstre
Page 62 and 63: Primary System ComponentsThermal pe
Page 66 and 67: Primary System ComponentsFan-powere
Page 68 and 69: Primary System Componentspowered VA
Page 70 and 71: Primary System Componentsinterfere
Page 72 and 73: Primary System ComponentsIf the des
Page 74 and 75: Primary System ComponentsTypically,
Page 76 and 77: Primary System ComponentsInterior z
Page 78 and 79: Primary System ComponentsInterior z
Page 80 and 81: Primary System ComponentsEqual fric
Page 82 and 83: Primary System Components• If nee
Page 84 and 85: Primary System ComponentsIn additio
Page 88 and 89: Primary System ComponentsAir-cooled
Page 90 and 91: Primary System Componentstemperatur
Page 94 and 95: Primary System ComponentsVariable-
Page 96 and 97: Primary System ComponentsFreeze pre
Page 98 and 99: Primary System Componentsrow coil i
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Primary System ComponentsThermal st
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Primary System Components(although
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Primary System ComponentsFigure 80.
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Primary System ComponentsA variable
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System Design Issues and Challenges
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System Design VariationsThis chapte
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System Design Variationspressure dr
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System Design VariationsImpact on o
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System Design Variations• Run 7 v
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System Design Variationsmechanical
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System Design Variations• Impleme
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System Design Variationsconventiona
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System Design VariationsFigure 113.
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System Design Variationsbuildings (
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System Design VariationsFor most ap
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System Design VariationsWhile the s
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System Design VariationsFigure 120.
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System ControlsThis chapter discuss
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System Controlssensor from being in
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System ControlsFigure 126. Modulate
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System Controlsfixed enthalpy contr
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System ControlsIf the air-handling
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System ControlsFigure 133. Floor-by
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System ControlsVAV terminal unitsSi
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System Controlspeople in a zone, an
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System ControlsAlternatively, if th
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System Controlsvariable-speed drive
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System ControlsFigure 137. System-l
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System ControlsTable 31. Example of
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System ControlsFigure 139. Morning
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System Controlszone to the unoccupi
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System ControlsThe optimal starting
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System ControlsFigure 143. Fan-pres
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System ControlsTable 36 lists condi
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System Controlsreset to be used dur
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System ControlsFigure 147. Ventilat
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System Controlsdecrease overall sys
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System ControlsFigure 150. Optimize
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GlossaryACH. Air changes per hour.A
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Glossarycondensing boiler. A type o
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Glossaryelectronic air cleaner. Par
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GlossaryMERV. Minimum Efficiency Re
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Glossarypump-pressure optimization.
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GlossaryTR. Cold-spot thermal resis
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ReferencesAir-Conditioning and Refr
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References______. 2009. Direct-Driv
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References______. 2008. “ASHRAE S
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Indexchilled-water system 79air-coo
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Indexhumidifiers 126humidity contro
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IndexVAV controlpressure-dependent
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Tranewww.trane.comFor more informat
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