VAV Boxes in North Carolina and South Carolina

Hahn Mason Air Systems is proud to be an integral part of the North and South Carolina building construction and mechanical equipment industry for over 84 years, serving you from our local offices and warehouse locations in Charlotte and Charleston. We represent one of the finest VAV Box manufacturers in Nailor and are proud to offer their technology to your next project.

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What is a VAV Box?

A Variable Air Volume (VAV) box, is a part of an HVAC (Heating Ventilation & Air Conditioning) system. It is located inside the duct work and is designed to control the air flow to a specific area, or also known as a “zone.” The VAV box regulates the volume of the air to the zone by opening or closing the damper, thus controlling the amount of conditioned air directed to the zone. In many cases, each zone within a facility has a thermostat tied to building automation system that controls the VAV box. These controls tell the VAV box when to open or shut the damper based upon the needs of the zone.

What VAV Boxes does Hahn Mason Offer?

As a long standing manufacturers representative for Nailor, we are able to offer a comprehensive line of air terminal units to meet the unique needs of your design or facility. The types of VAV boxes we offer include:

How to Size Terminal Units (VAV Boxes) with & without Hot Water Coils

Our engineering and sales staff are ready to serve you in solving your equipment selection and delivery challenges. Our highly trained team assists consulting engineers, architects and contractors regularly in the selection and application of VAV boxes helping you achieve optimal results.

The normal thought in sizing single duct vav terminal units is easy.  Look on the CFM chart and stay within the minimum and maximum CFM range of the unit size.  Or is it that simple?

What are some of the parameters to consider when sizing a VAV Box Terminal Unit?

1. System operating pressure measured as static pressure (sp) as it relates to noise levels (NC).
2. Terminal Unit air flow pressure drop.
3. Hot water coil entering water temperature (EWT) as it relates to the amount of heat the hot water coil can produce.
4. Air handling unit (AHU) System operating pressure.  Most systems are approximately 1” static pressure.  But larger buildings require larger AHU’s and therefore higher static pressure capabilities.  Terminal units close to an AHU may see up to 2.5” sp while units farther away at an end duct run may only see .2” sp.  The higher the system static pressure, the greater the noise levels. (NC).  Radiated and discharge.   Most project schedules currently require NC levels as low as 25. Well you can imagine the more air that pushed through a VAV box the more noise it will generate.
5. VAV Box air flow pressure drop is another consideration.  Standalone unit do not have very much pressure drop.   However, units with hot water coils can.  Hot water coils are used to raise the AHU air temperature up to a “human comfort” level.  Typically, 1-row or 2-row coils satisfy this requirement. Many project schedules show a max air flow pressure drop of .3” sp.  This number is usually easily achievable when sizing units based on NC levels.
6. Hot water coil EWT.  Years ago, just about every schedule showed the EWT to be 180 degrees F.  (Hence, human comfort being satisfied with one or two row coils.)  Currently, due to huge improvements in boiler efficiencies many schedules use a EWT as low as 130 degrees F.  Now, in order to satisfy the design conditions for human comfort we may need to: (a) add rows of hot water coils and (b) oversize the terminal unit.

Naturally, there are additional factors to consider; however, taking into consideration the points above will help you ensure that the terminal unit selected will achieve the design intent.