Exhaust systems often account for more than 20% of a laboratory facility’s HVAC energy costs. Meanwhile, high exhaust stack velocities are typically maintained in excess of what is necessary for all but the most extreme conditions, despite the fact that the air being exhausted is usually “clean” for a majority of the time. This results in wasted energy, but is also an opportunity for additional energy savings in critical spaces.
Most often laboratory and vivarium exhaust fans operate at a constant volume or are controlled by staged manifolded fans. This may be the case even if the lab controls are variable volume. The fans typically include a bypass damper used to maintain a constant total exhaust and therefore a constant velocity within the exhaust stack. These systems are usually configured to operate with high stack velocities in order to deliver dilutions levels of 3000:1 or higher, regardless of the current chemical usage activity within the facility at that time. This results in unnecessary energy use when the exhaust stream is clean. Many buildings also have lower profile entrainment fans, which demand higher velocity and more energy in order to prevent re-entrainment. With external emissions being clean a majority of the time, Aircuity’s solution takes advantage of the opportunity to reduce stack velocity.
Aircuity’s approach monitors for contaminants within the exhaust plenum. These measurements are then compared against a contaminant threshold which, when exceeded, triggers the fan system to a higher stack velocity resulting in greater dilution performance (e.g. 3000:1 dilution). Under clean, or relatively clean conditions, the fan system will be configured to operate at a lower stack velocity, yielding lower dilution levels but at a value (typically 750:1) that is sufficient for the majority of the contaminants that may be used within the facility. This ensures a tremendous margin of safety, while providing significant energy savings. Intelligent data and information on equipment performance and environmental parameters are displayed on Aircuity’s dashboard for 24/7 access.
The demand based control of a lab facility’s exhaust fans is an important complement to Aircuity’s lab solution, resulting in a comprehensive reduction in energy use while providing a healthy and safe environment for occupants.
For more information about Aircuity and how we can provide you with their demand control ventilation solutions contact us today at 860.291.8886, email Tom Proietti. You can also visit us on the web. Don’t forget to follow us on social media: Twitter, LinkedIn, Google+, facebook and YouTube.