Indirect Fired Air HandlersAt Rapid Engineering, we offer the 8500D Series of Indirect Fired Air Handlers, which are designed to heat, cool and/or pressurize a building, depending on each facility's needs. The 8500D Series features indirect fired gas heating via a fully welded drum and tube heat exchanger design.  Indirect fired air handlers are typically used instead of direct-fired air handlers where codes or building space classifications do not allow open-flame combustion heat sources or where codes or building classifications prohibit any products of combustion to enter the supply airstream.

Our heavy duty, indirect fired air handlers and make-up air units are available in three different operational configurations:

  • Make-Up Air configuration (MUA): Supplies 100% outside air for direct replacement of building exhaust. It works perfectly for water treatment plants, and buildings with industrial processes that incorporate mechanical exhaust.
  • Fixed Recirculation configuration (FR): Provides a manual selection of outdoor air from 0% to 100% allowing the user to easily select how much make-up air and how much return air is supplied to the building.
  • Air Management (AM) configuration: Provides an automated mix of return air and outside air with the use of a pressure sensor, which automatically responds to building pressure and temperature needs. These are usually used in industrial and commercial buildings that have air management requirements that vary from hour to hour and day to day. 

 Benefits and Features

The rugged, heavy-duty construction includes a welded steel frame and casing. Motors, belts and bearings are placed out of the air stream, which provides for easier maintenance and increased part longevity. With a welded drum and tube heat exchanger, these units are well suited to applications which are sensitive to the introduction of heated air containing any combustion by-products. Additionally, there are various discharge options to choose from allowing for an optimal location for any buliding:

Indirect Fired Air Handlers

  • Horizontal unit with horizontal discharge
  • Horizontal unit with bottom discharge
  • Horizontal unit with top discharge
  • Upright unit with top discharge
  • Upright unit with bottom discharge
  • Upright unit with top left discharge
  • Upright unit with top right discharge
  • Upright unit with bottom left discharge
  • Upright unit with bottom right discharge



 Pair it with Cooling

During the warm weather, the fan can operate as ventilation for cooling, or the air handler can be equipped with mechanical cooling. We have available two cooling options: DX cooling coils or chilled water coils.

Cooling options can be added by simply installing coil sections equipped with the appropriate cooling coils and a condensing unit or chiller.

 The Rapid Engineering experience 

We've been in business for over 50 years, providing thousands of customers professional and expertly crafted results. A Rapid Engineering representative will be there with you every step of the way - we support clients in design application to make sure the HVAC system is well suited for your building. Units can be installed either horizontally or vertically, inside, outside or suspended in a roof deck.

For more information or to speak to one of our experts, please contact us.