HVAC

HVAC

1. AHU

   • Damper
     • adjust air volume flow rate by altering air passage cross-section with opposing blades rotating on horizontal pins.
     • opening control by servo motor handled by automatic control syustem.
     • Parallel blades
       • deflection and shut-off purpose
     • Opposing blades
       • controlled synchronously
   • Mixed Air Chamber
     • 2-way
       • outdoor ventilation mix with return air
       • minimize energy consumption
     • 3-way
       • incorporates separate return air fan
       • use opposing blades damper
     • free cooling
       • when outdoor isat or slightly below indoor design T
       • activated by having outdoor air damper on open position to supply up to 100% outdoor air without operating air-conditioning equipment
   • Air Filter
     • Mechanical
       • Bag Type
         • MERV: 13-16
       • Box Type
         • high efficiency particulate air (HEPA)
           • MERV: 17-20
         • ultra low penetration air (ULPA)
           • MERV: 17-20
       • Pleated Type
         • MERV: ~6
     • Elastrostatic
       • >95% on Arrestance (not efficient) scale
       • washable
       • MERV: 4
     • Minimum Efficiency Reporting Value (MERV)
   • Air Conditioning Source
     • Heating
       • furnace
       • boiler
     • Cooling
       • DX Coil
       • Water Coil
   • Humidifier
   • Supply Air Fan
     • fan position
       • Draw-through
         • generate better uniform air flow across cooling/heating source
         • carry over condensation from cooling source due to air dehumidification
       • Blow-through
     • fan type
       • centrifugual
         • pulled along fan shaft and blown radially away from shaft in scroll casing
         • forward curved (FC)
         • backward curved (BC)
           • Airfoil fan
             • centrifugal fan with BC blades thickened twice
             • highest efficiency
       • axial
         • pulled along fan shaft and blown along in same direction
         • propeller
         • tubeaxial
         • vaneaxial
   • Air Distribution
     • Air conveyance
       • fittings
       • ducts
         • metal duct (rigid)
           • least heat loss/gain
           • least fan operating cost
         • non-metal duct (flexible) - fibreglass
           • insulation
           • light weight
           • low cost
           • sound absorbing
           • rectangular: fibreglass board
           • round: fiberglass aluminum foil
         • noise reduction
           • vibration
             • canvas (flexible) connection @ inlet & outlet opentings
           • residual
             • inner duct surface with acoustical board
         • return air
           • return-air plenum space for small area
             • vast space in drop ceiling
           • low air velocity for noise reduction
     • Room distribution
       • ceiling distribution
         • ceiling/linear diffuser
           • include volume control damper
           • excellent for cooling & heating
           • without undue draft or local discomfort
         • cooling only
       • inside wall distribution
         • register
           • grille with volume control damper
       • perimeter distribution
         • along exposed perimeter of space
         • optimum comfort for winter heating
       • grille
         • fixed/adjustable blades directing flow only
       • air outlet performance
         • noise
           • noise criteria (NC)
             • increase NC, decrease size of outlet
         • outlet/face velocity
           • 500 to 800 fpm
         • throw
           • distance b/w outlet and occupied zone
         • drop
           • vertical distance supply air has fallen at the end of throw
         • terminal velocity
           • 50fpm at the end of throw