What is a Terminal Unit in an HVAC system?
A small component that contains a heating coil, cooling coil, automatic damper, or some combination of the three. Used to control the temperature of a single room. Abbreviated TU.
In an HVAC system, the terminal unit is the point at which conditioned air is delivered to the space. The objective of the terminal unit is twofold:
- first, mix the correct proportion of hot and cold water to provide the desired supply of air temperature;
- second, to deliver the air at a constant volume.
Depending on the application, there are many different types of terminal units available on the market today.
How does a terminal unit work?
The terminal unit is responsible for mixing the correct proportion of hot and cold water to provide the desired supply of air temperature. It does this by using a heating coil and a cooling coil. The heating coil heats up the air as it passes through it, and the cooling coil cools down the air as it passes through it. The two coils are controlled by an automatic damper that opens and closes depending on the temperature of the air passing through it.
When the air reaches the desired temperature, the damper will close and the air will be delivered to the space at a constant volume.
What are some benefits of using a terminal unit?
There are many benefits to using a terminal unit in an HVAC system:
- One benefit is that it allows for individual room temperature control. This is because each terminal unit is responsible for controlling the temperature of one specific room.
- Another benefit is that it can help to improve indoor air quality by delivering fresh, conditioned air to the space.
- Additionally, using a terminal unit can help to save energy and lower utility bills, as the system will only heat or cool the space as needed.
Single duct terminal unit
The single duct terminal unit (SDTU) is the most basic type of terminal unit. It consists of a heating coil, cooling coil, and blower assembly. The SDTU is connected to the ductwork system and delivers air directly to the space through diffusers or grilles.
Fan powered terminal unit
The fan-powered terminal unit (FPTU) is a type of terminal unit that uses a fan to provide air movement. The FPTU typically consists of a heating coil, cooling coil, and blower assembly. These components are all housed in a cabinet that is usually made of sheet metal. The FPTU is connected to the ductwork system and delivers air directly to the space through diffusers or grilles.
Chilled water terminal unit
The chilled water terminal unit (CWTU) is a type of terminal unit that uses chilled water to provide cooling. The CWTU typically consists of a cooling coil and blower assembly. These components are all housed in a cabinet that is usually made of sheet metal. The CWTU is connected to the ductwork system and delivers air directly to the space through diffusers or grilles.
Is a terminal unit the same as a VAV?
No, a terminal unit is not the same as a VAV. A terminal unit is a small component that contains a heating coil, cooling coil, automatic damper, or some combination of the three. It is used to control the temperature of a single room. Abbreviated TU.
A VAV is a type of terminal unit that is commonly used in commercial applications. VAV units are similar to FAUs in that they consist of a heating coil, cooling coil, and blower assembly; however, VAV units also have an additional component called a VAV box. The VAV box is used to control the volume of air that is delivered to the space.
What is an air terminal device?
An air terminal device is any device that is used to help control the temperature of a space. This can include items such as thermostats, humidifiers, and dehumidifiers. An air terminal device is also sometimes referred to as a terminal unit.
Related Links
Engineering Guide – Terminal Units
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