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.


  • 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.
  • 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.
  • 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.
How It Works

The vertical LJ Wing FAS can be used for preheating combustion air to improve boiler efficiency.

The vertical LJ Wing FAS can be used for preheating combustion air prior to entering the boiler. DOE studies report boiler efficiency improves up to 1 percentage point for every 40 degrees of combustion air preheating. The vertical FAS unit is also used in applications where make up air is required to offset air that is exhausted in a process situation. Cold outside air is drawn downward through the unit using a factory integrated blower system and in the process the cold air passes over an LJ Wing Integral Face and Bypass coil. The LJ Wing Integral Face and Bypass coil controls the leaving air temperature by opening and closing bypass dampers in response to a discharge thermostat. An intake damper is also available to provide a cold air shutoff when the unit is not in operation. During milder or warmer months of the year the FAS can also provide air circulation that can help improve employee comfort and efficiency.

Blended air streams for reduced energy use

Optional mixing box air blending configuration.

The vertical FAS can also be equipped with a mixing box for reducing energy use by recirculating room air when appropriate. This illustration also shows a typical installation with a roof mounted intake "mushroom" by others and one of the several optional LJ Wing air discharge systems.

Widespread temperature distribution

LJ Wing revolving discharges provide broad temperature distribution.

The optional LJ Wing revolving discharge shown in the main product image is designed to distribute tempered air over a broad area...similar to a large ceiling fan. CFD studies illustrate how the slowly revolving air discharge system...rotating at 1 rpm... provides a full circle of tempered air covering large areas of the building space. With fan motor options of up to 44hp, the Wing Fresh Air System with revolving discharge has the ability to cover large areas from mounting heights up to 70 feet.

The unique LJ Wing revolving discharge system.

The high torque, low rpm, rack and pinion system of the Wing revolving discharge system.

The LJ Wing revolving discharge system has been in existence over 30 years, providing an airflow pattern that mimics a ceiling fan but covers large areas from tall mounting heights. The heart of the revolving discharge is the high torque motor that is "geared down" to turn the discharge system at roughly 1 revolution per minute.