Custom Air Handling Unit Design Critical Decisions

The design of an air handling unit is a major decision and is a complex and sophisticated activity but here are the critical design decisions when designing a custom AHU.
Enclosure Construction

  • Structural Capacity and Air Tightness
    1/200th of the span deflection and less then 1% casing leakage at 1.5 times the total of the unit static pressure profile
  • Corrosion Resistance/Unit Life Span
    Aluminum or ThermoComposite – 30+ year life
    Galvanized Steel – 10-15 year life before major repairs may be required
  • Rigid Foam vs Fibrous Batt Insulation
    Foam provides significant strength, rigidity and air leakage control vs batt insulation at minimal or no added cost

Component Velocities (minimum velocities apply in VAV systems)

  • Recommended Velocities For Optimum Performance and Energy Use
  • Cooling Coils 450 fpm max, 250 fpm min
  • Heating Coils 800 fpm max, 250 fpm min
  • Media Filters 350 fpm, 150 fpm min
  • Steam Humidifiers 800 fpm, 350 fpm

Use of Air to Air Energy Recovery

  • Air to Air energy recovery can be applied in 100% OA and partial OA AHU’s
  • Choose either hi efficiency run around glycol, sensible or enthalpy plate exchanger, rotary enthalpy wheel or heat pipe

Indoor Air Quaility

  • Level of Filtration
  • Odor Control

Sound Control

  • Does system require interior acoustical treatment or sound attenuators

Type of Fans

  • Fan Array vs individual fans
  • N+1 fan redundancy
  • AC motors w/ VFD’s vs ECM Fans


  • Component removal and service
For More Information - askRick



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