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What is a Terminal Unit?

Posted by Price Industries on February 25, 2020 at 8:52 AM
Price Industries

A Simple & Cost-Effective Device for Zone Airflow Control

The control of air distribution in modern buildings is typically accomplished by the use of air terminal units. A terminal unit is a device that is used to regulate the volume of conditioned primary air from the central air handler to the occupied space. Watch this video to learn more!

Terminal units are available in several different types, each designed to suit specific applications.The terminal unit types listed below are the most common configurations used in the HVAC industry. 

Single Duct

The single duct is the simplest and most cost-effective type of terminal unit, and is commonly referred to as a VAV box. Typical single duct construction includes:

  • a round inlet where the flow sensor and damper are mounted
  • a rectangular casing that incorporates a liner with acoustic and/or thermal benefits.

Fan Powered

A fan powered terminal unit, commonly referred to as a fan powered box, is an air terminal unit which contains both a primary air inlet, as well as a local motor and blower assembly. Fan powered terminals generally come in either a parallel or series arrangement, determined by the location of the fan in the assembly. A series fan powered terminal unit with a sensible cooling coil is available for zone control in a dedicated outdoor air system (DOAS).

Dual Duct

non-mixing dual duct terminal is essentially two single ducts fastened together with one common discharge opening. The inlets are connected to two of the following: cold air, warm air, or fresh air. A mixing dual duct terminal unit is similar to the non-mixing type, but has an integral mixing section between the two supply valves and the discharge duct connection. Different levels of mixing performance are available.

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To learn more about terminal units, visit our Terminals site or contact an Application Engineer at

Topics: Terminals, System Efficiency, HVAC Fundamentals, Design Engineering, Training, Architecture

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