Diffusers Table of Contents - Trane

1 VAV-PRC008-END 1 IntroductionD 2 3 Linear Slot Diffusers (LINR)D 4 11 Adjustable Flow Diffusers (FAPF, VAPF, AABD, VAPS)D 12 21 Light Fixture Diffusers (LITE)D 22 26 Induction Diffusers (INDT, INDB, INCB, INSR)D 27 29 Perforated Diffusers (PERF)D 30 32 Mechanical SpecificationsD 33 34 IntroductionIn today s diverse buildingenvironment, we are seeing anexpanding role of VAV applicationsacross many different marketsegments. While this is happening,it is necessary to make sure the VAVsystems and Diffusers in particularare applied, installed, and purpose of this section of thecatalog is to show these issues thatneed to be considered when selectingand placing (OPTIONAL)CONTROLUNITT able ofContentsDiffusersD 2 VAV-PRC008-ENDiffusersThe VariTrane line of variable-air-volume (VAV) products has been anindustry leader in performance andquality for many years.

2 While mostwould associate the VariTrane namewith VAV terminal units, the diffuserproduct line has grown significantlyover the Air DistributionWhen variable-flow cooling andconstant-flow heating are combined ina zone, the zone air Diffusers areusually selected at partial cooling loadto ensure proper operation. Ceiling-mounted linear slot Diffusers arerecommended since they perform wellover a wide range of velocities. Cool airdelivery takes advantage of the Coanda effect, whereby cool airdischarged through a linear slotdiffuser hugs the ceiling beforedescending, insuring proper operationover a wide range of flows without dumping. When delivering warm airwith constant flow velocities, or warm/cool air with variable flow velocities,the flow velocity must be high enoughto ensure that the air reaches the prevent stratification, the warm airtemperature should not be more than20 F ( C) above the zone addition to choosing the correctdiffuser type, the designer mustproperly size and place each diffuser inthe zone to minimize noise andpressure drop while maximizing thethrow and diffusion Diffuser TypesThe VariTrane line of Diffusers containsa variety of different models.

3 Thefollowing is a list of the diffuser typesin the VariTrane line,an explanation ofeach type, and a shortdiscussion of theproper application foreach slot diffuser (LINR)Linear slot diffusersare most commonlyused in VAV DIFFUSERSAIR DIFFUSERSRETURNRETURNAIRAIRDIFFUSERDIFFU SERNEVER DO NEVER DO THIS!!THIS!!(PERPENDICULAR AIR FLOWS)nominal airflow. If you start by using100% of the nominal airflow, you willend up with high losses inperformance, acoustical problems, andvery little or no design diffuser airflow rate is 50 cfm perlinear foot ( L/s per linear meter) ofdiffuser. Therefore, the recommendedflow to use when designing is 50 cfm/linear ft x = 40 cfm/linear ft ( L/s/linear m x = L/s/linear m).The nominal airflow of a diffuser isdetermined by multiplying the diffuserlength, the number of slots, and theairflow per linear foot.

4 Using theairflow per linear foot calculated above,a 4 foot, 2-slot, 2-way diffuser shouldbe designed to handle 4 linear ft x 2slots x 40 cfm/linear ft = 320 cfm( m x 2 slots x L/s/linear m = L/s).To maximize the effectiveness ofventilation with ceiling Diffusers ,throws should be kept as long aspossible. For proper air circulation, tryto maintain at least a 20 F ( C)difference between the supply air androom temperature. This provides foroptimum Velocities The collisionvelocity is the speed at which movingair meets a wall or another airflowThis type of diffuser has a fixed vaneinside, which means that the pattern isnot adjustable. The fixed vane allows awide range of flows through thediffuser without causing drafts. Lowerflanges provide ceiling tile support asan integral part of the diffuser Guidelines LinearSlot DiffusersDiffuser Placement The maximumrecommended distance betweendiffusers is three diffuser lengths.

5 Forexample, if the diffuser length is 4 feet( m), the maximum separationdistance would be 4 ft x 3 = 12ft( m x 3 = m).The maximum recommended distancefor Diffusers from an exterior wall, withparallel flow to the wall is two diffuserlengths. For example, if the diffuserlength is 4 feet ( m), themaximum distance from the exteriorwall would be 4 ft x 2 = 8 ft( m x 2 = m).A simple rule for better air circulation isto avoid placing supply air linear slotdiffusers that allow airflows to collideat right Guidelines Whenbeginning the placement and layout ofdiffusers, assume that each diffuserdelivers only 75% to 80% of itsDiffusersIntroductionVAV-PRC008-END 3 INTERIOR INTERIOR WALLALL75 FPM75 FPM150 FPM150 EXTERIOR WALLALL stream. For exterior walls, the collisionvelocity should be between 100 and150 feet per minute (FPM) ( m/s).

6 Do not exceed 150 FPM( m/s) on an exterior wall. Forinterior walls, the collision velocityshould be between 50 and 75 FPM( and m/s). Try not to exceed75 FPM ( m/s) for interior maximum recommended collisionvelocity between airflow streamsshould not exceed 150 FPM ( ). The collision velocity betweenairflow streams is determined by theaddition of both velocities at the pointof collision. Avoid collision of airvelocities at right angles to each otherby trying to maintain parallel this guideline will allow oneto maximize the "Coanda" effect andproper air diffusion in a indicates that mixed airafter collision near the ceiling andbelow 150 FPM will produce comfort inthe zone at the occupant's Air Slots Return air slotsare placed perpendicular to supply airslots. This prevents supply air frombypassing the space, and allows forproper air circulation.

7 With asuspended ceiling, low operating staticpressure across the ceiling panels mustbe maintained. Failure to do so willcause the return air to be forcedaround the edges of the ceiling this happens, soiling of thepanels will occur and the mechanicalsystem can become choked for returnair. A space-to-plenum pressure dropof to inches of water isacceptable under most Adjustable Pattern Flow (FAPF) The FAPF diffuser, a type of ceilingdiffuser outlet, should be used with lay-in ceilings. The primary benefit of thiskind of diffuser is that it provides themost flexibility of adjustment of theairflow pattern. The FAPF diffuserprovides adjustable vanes forhorizontal or vertical throw. The dual-vane option allows each slot to beadjusted for left, right, or vertical pattern adjustments, the vanesalso provide airflow dampering.

8 Inaddition, the vanes are adjustable fromthe face of the diffuser so changes tothe pattern can be made after thediffuser is Adjustable Pattern Flow (VAPF) The VAPF diffuser is very similar to theFAPF ceiling outlet Diffusers . Theprimary difference is the design of thepattern adjustment vane. The VAPF diffuser should be used with lay-inceilings. The pattern is adjustable forhorizontal left, horizontal right, orvertical throw. The pattern adjustmentvane contains a felt seal on the end toreduce air leakage around the vanes are adjustable from the faceof the diffuser, allowing the pattern tobe easily changed after Adjustable Pattern Flow Special (VAPS) The VAPS diffuser is a special versionof the VAPF diffuser. The design of thevane is slightly different from the VAPF model, but the VAPS has the samefunctionality. The VAPS has beenpopular in certain regions of Air Bar Diffuser (AABD) The AABD diffuser is another lay-inceiling type of diffuser.

9 The differencebetween the AABD and the FAPF or theVAPF is that the AABD has noadjustment vane. A sliding air bar inthe outlet of the diffuser makes thepattern adjustments. The pattern isadjustable for horizontal left, horizontalright, or vertical Fixture Diffuser (LITE) The LITE diffuser should be installedon a suspended ceiling light type of diffuser is quite popularwith architects, because the number ofceiling penetrations can be diffuser is available with anintegral sliding volume damper andwith or without pattern control vanes(some light fixtures already containpattern control vanes). Both thevolume damper and the patterncontrol vanes (if necessary) areadjustable with a screwdriver from theface of the diffuser without removingthe light fixture doorframe. The patterncontrol vane allows for eitherhorizontal or vertical Diffusers (INDT, INDB, INSR,INCB) Induction diffuser discharges air in atight pattern along a ceiling.

10 Thedischarged air then induces the roomair into the air stream to effectively mixthe streams. Induction Diffusers aretypically used in exterior zones thathave unusually high heat loads ordrafts. They are designed to beinstalled in suspended ceilings andhave high induction horizontal center down blow option providesa vertical air pattern for exterior wallsor glass. Induction Diffusers haveadjustable blades for volume anddirection This type of induction diffusercontains a supply air outlet only. It willproject air along a ceiling and providemixing of the primary and room This type of induction diffusercontains a standard supply air outletalong with down blow outlet. Thedown blow outlet will project a jet ofprimary air in a vertical direction whilethe standard outlet projects theinduction jet. The down blow jet isoften washed along an exterior glasswindow or aimed to combatsomething that is producing a draft inthe This type of induction diffusercontains a supply air outlet along witha separate return air inlet integratedinto one device.