Using VFD’s on powered exhaust

A quality powered exhaust system as part of your rooftop air conditioner  can create a big difference in overall HVAC performance. Implementing a variable frequency drive (VFD) into powered exhaust can improve building comfort and maximize free-cooling economizers.   

As outside air increases during the spring, fall and winter months for compressor-free cooling, building exhaust needs to vary for tighter buildings.  By maintaining a consistent space pressure, outside air is maximized, thereby increasing your cooling capability and saving significant energy costs by not using constant volume exhaust fans.

Many buildings operate with VFD’s on the supply fan motor.  For VAV systems, VFD’s throttle back the power required during part-load conditions – which is over 90% of the time. However, many times exhaust fans are overlooked.  Often times exhaust fans turn on or off dependent on building pressurization. By using VFD’s on exhaust, a carefully calibrated VFD typically results in energy savings somewhere between 35 and 50 percent. Most units will achieve a return on investment within two years—some will pay for themselves as early as six months.

Motors also experience a reduction in wear when managed by a VFD, as they run at a controlled rate matched to need instead of stop/start then rushing back to full power on a regular basis.  The VFD utilized in Ruskin Rooftop Systems’ centrifugal power exhaust systems also improves pressurization control as needed for varying amounts of outside air, maximizing the normal benefits of utilizing outside air via rooftop units.

If you would like to learn more about the applications of variable frequency drives in powered exhaust solutions, or have questions about other commercial HVAC accessories, you can contact Ruskin Rooftop Systems and find out more. Ruskin Rooftop Systems has been a leading manufacturer of accessories for commercial HVAC equipment for over 30 years.


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