What is an air terminal unit? Why is it used?
What You Need to Know About Air Terminal Units
If you’ve ever walked into a cool building after being outside in the heat, you were probably thankful for that cold, refreshing air. But how does that nice, cool air get throughout the whole building? If it’s a larger building or commercial space, then an air terminal unit is probably responsible for dispersing that cool air throughout the space.
But, what is an air terminal unit?
An air 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.” Basically, this is what controls the amount of cool air being blown into a room.
How does it work?
When cool air flows from the central air handler and reaches the air terminal unit, an air flow sensor measures the difference between the total and static pressure. Then a terminal controller takes that data and uses it to determine the rate of the air flow through the inlet. The controller then adjusts the damper, which allows more or less air through the unit depending on what is needed to meet performance requirements and maintain optimal comfort in the space.
Why is air flow important?
By controlling the volume of air distributed into a space, the terminal unit allows the desired temperature to remain constant. Yes, this is an important factor in keeping people comfortable, but air flow also contributes to the health of people in a confined space. According to the CDC, increasing air flow in a building “can reduce the risk of exposure to the [COVID-19] virus and reduce the spread of disease.”
What are the different kinds of air terminal units?
Let’s look at three of the most common types of air terminal units
- Single Duct
A single duct unit, also known as a VAV, is the simplest type of terminal unit. The set up of a VAV involves “a round inlet where the flow sensor and damper is mounted, followed by a rectangular casing that incorporates a liner with acoustic and thermal benefits.”
- Dual Duct
The dual duct comes in both mixing and non-mixing types. The non-mixing unit is basically two single units put together with one opening for discharging air.
The mixing unit has a mixing section between the two supply valves and the discharge duct connection which allows for different levels of performance.
- Fan Powered
The fan powered terminal unit, also known as a fan powered box, includes a main air inlet and a motor and blower assembly. Fan powered units typically come in one of two arrangements: Parallel or Series. The Parallel arrangement has a combination of fan-air and air from the central air handler.
The Series arrangement is a combination of air from the inlet and air from the return air opening.
Blog sources and images: Price Industries