Fresh Air Supply Units

The Fresh Air Supply (FAS) provides a versatile heating system for installation in wall openings or with roof mounted intake hoods. It combines up to a 44HP fan with a unique damper modulated, air flow system, over hot water or steam coils to deliver up to 26,000 CFM of temperature controlled make-up air. The roof mounted units with optional revolving discharge provide ceiling fan like air flow for summer comfort.

Product Details:
  • Unique Integral and bypass damper modulated, air flow system, over hot water or steam, 3/8" fin tube IFB coil to regulate the outlet temperature.
    L.J. Wing Fresh Air Supply Units
  • Four methods of outside airflow control available:
    • Two-Speed Motor: Optional two-speed motors for two stages of airflow.
    • Mixing Box: A mixing box matches outside air intake to the demands of the boiler(s)
    • Variable Frequency Drive: The delivery of outside air can be modulated as the demand for combustion air changes.
    • Multiple FAS units: Each FAS unit serves the combustion airflow needs of a single boiler in a gang.
  • Two control configurations available:
    • Airstream control, a single sensing element located in the discharge airstream.
    • Room with Low Limit control uses the airstream controller as its low limit and adds a room thermostat as the primary control.
  • Single phase or three phase propeller fan. Belt or direct drive configurations available.
  • Horizontal units mount easily on a side wall and require no floor space. Vertical units leverage roof mounting with optional revolving discharge.

Click here to see our new High Static Fresh Air Supply that provides the same benefits as the FAS for applications requiring ducting or filtration, supporting up to 2.5 inches of accessories!



  • Increase boiler efficiency by 1% for every 40 °F of preheat.
  • Leverage excess boiler capacity to deliver temperature controller make-up
  • Offers freeze protection of unit and surrounding area improving the reliability and safety of boiler and turbine room operations.
  • Provides make-up air for processes including water treatment, painting, plating, welding, etching, and chemical processing.
  • Supports up to 49.862 MBH of boilers.
  • Replaces up to 80% of louvers.
  • Extends boiler life.
  • Offers design flexibility, requiring no floor space and small wall or ceiling openings.