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Airflow and Static Pressure with Loren Cook Company Coffee Break Recap

Loren Cook SQN Centrifugal Square Inline FansWhat is the Relationship Between Airflow and Static Pressure in a Ducted Air System?

We dropped in on Chris Curry at Loren Cook for this coffee break, who offered an excellent demonstration that definitively answered this question.

If you couldn’t join us on the webinar, here’s some of what you missed.

The goal with ducted airflow is to design a system that minimizes the amount of static pressure (resistance to airflow) while not oversizing the duct to the point where it won’t fit or becomes too expensive for the project (due to the amount of metal needed). The less static pressure, the less energy the fan consumes to deliver the required airflow.

Curry illustrated that by pointing out the Third Fan Law: When increasing a fan’s RPM, the horsepower required by the motor to turn the fan wheel increases by the cube of the change in motor speed. For example, if you want to increase fan RPM by 10%, the energy required to turn the fan increases by 33.1%.

Keep this in mind when you consider energy optimization in a ducted system. It’s good to seek out equipment with high EER ratings and motor efficiency. But also make sure that your duct design is optimized. This includes the size of the ductwork (which affects the velocity of the air moving through it) and the fittings that you specify in the design (which affects both the pressure drop and system effect associated with the installed duct system).

It only takes one improper fitting to increase static pressure at a magnitude that wastes all the efficiency you’re gaining from a premium fan motor.

Which duct fittings have the most significant effect on static pressure?

Curry arranged a 12-inch utility set fan with 2 ½ duct diameters of straight duct on the discharge end to achieve laminar flow. He then measured the drop in static pressure in the system when he attached fittings to the end of the duct.

Straight Elbow

Contractors assume the pressure drop of this fitting will be about .15 inches (an old rule of thumb says an elbow equals roughly the same static pressure as 100 feet of duct). Surprisingly, it’s more than double that (around .3). This fitting creates an eddy behind the throat of the fitting, drawing air into the duct and creating turbulence.

Straight Elbow with Turning Vanes

The addition of turning veins in a straight elbow brought the static pressure drop to only about .07. The downside is that the vanes can gather debris inside the duct, so Curry recommends installing an access door upstream of any elbow with turning vanes.

Short Radius Elbow

Curry admitted this fitting is controversial and sometimes not approved for installation. He demonstrated that the 13” radius elbow had a .06–.07 drop in static pressure, as good or better than the straight elbow with turning vanes. The problem with that elbow is that you need to have the space for the short radius elbow to curve — lots of mechanical rooms don’t have that space.

Square Throat Radius Heel Elbow

You might think that combining the square throat of the straight elbow with a radius heel would give you the benefits of both elbows. You might expect a static pressure drop between .06 and .3 (something around the standard guess of .15).

It’s worse than both. There’s a misconception that the airflow follows the radius heel’s curve. Instead, that same negative eddy created by the square throat is made worse because this elbow creates a pinch point (it has a smaller diameter in the middle than either end).

45-Degree Radius Elbow

This is the solution to the previous fitting — modifying the throat from a 90-degree angle to two 45-degree angles to remove that pinch point and keep the cross-section distance consistent through the elbow. That’s a truer compromise: the static pressure drop is close to the .15 standard guess.

Long Sweeping Radius Elbow

The one everyone wants — a long, graceful, gentle arc. Curry used a 20” radius elbow, one and half times the duct diameter. And sure enough, the static pressure drop is negligible (roughly .02–.03). But the practical problem remains. This elbow costs more and takes up even more leasable space than the short radius elbow. That’s a significant amount of money and real estate throughout an entire building’s ductwork.

Radius Elbow with a Splitter

Here’s the best of all worlds: Static pressure drop was .02–.03, significantly better than the short radius elbow. The split inside the duct turns this 13” short radius elbow into two long radius elbows of 5” and 8”, giving you the airflow benefits of a long curve in a short space.

Curry also discussed tee fittings and fittings on the fan’s inlet side. Are you curious why a fan’s submitted performance doesn’t always match a test and balance report? Or whether a forward-curved vs. backward-curved fan wheel makes any difference in the efficacy of these fittings? Contact an SVL sales engineer, and they’ll let you in on what you missed.

Speaking of which…

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                      Jim Lubratt

                      President & Chief Executive Officer

                      Jim Lubratt has been president of SVL since 2006. He first joined the company as a sales engineer in 1992 and was made a partner in 2000. He holds a Bachelor of Science in mechanical engineering from Southern Methodist University and first entered the HVAC industry as a marketing engineer for a heat pump manufacturer in Texas.

                      In addition to his role at SVL, Jim is vice president of AQC Industries, LLC, a manufacturer of specialized underground ductwork systems. He is also an investor and board member for Hydromx, Inc., a manufacturer of heat transfer nanofluids, and Crotega, Inc., creators of personal and building security solutions.

                      Jim and his wife, Tracy, met in college and married in 1993. They have three children, two of whom have graduated college in Texas, while their youngest is attending Grand Canyon University in Arizona.

                      Outside of work, Jim places a priority on his faith, family, friends, and fitness. He enjoys helping people-supporting charities, time with his wife and kids, road-biking with friends and efforts to stay physically fit.

                      A message from Jim on the achievements of SVL

                      SVL started in February 1967 by Charlie Schwab and Craig Vollhaber. Schwab-Vollhaber, Inc. (as it was named at the time) steadily grew and, in 1985, welcomed Paul Lubratt as another partner, becoming Schwab-Vollhaber-Lubratt, Inc. SVL’s founders had the determination to build the most talented, customer-focused HVAC representative in the Midwest. Our original drive and passion still shape the company and culture to this day. The achievements of an organization are the results of the combined efforts of every individual. From humble beginnings, SVL founders paved the way to industry success with hard work and determination. “Today, SVL is strongly organized with great people to lead our industry forward as we are challenged with fast-paced changes to reduce our environmental impact,” says Jim. Now, 55+ years later, SVL is under the leadership of two new principals who share the same vision and drive that has propelled SVL throughout the years. Built on a foundation of integrity, Jim Lubratt, and Charlie Vollhaber strive to ensure opportunities for personal growth, improved work environment, and shared life enrichment. The achievements of our organization are the results of the combined efforts of every individual.

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                      Charlie Vollhaber

                      Executive Vice President & Officer

                      Charlie Vollhaber is a third-generation employee at SVL, as a grandson of company co-founder Craig Vollhaber and son of former CEO Todd Vollhaber. Charlie holds a Bachelor of Science in mechanical engineering and an MBA, both from the University of Minnesota. He became an outside salesman for SVL in 2013, was made a partner in 2019, and then executive vice president and officer in 2022.

                      He grew up playing sports, including football, basketball, golf, and track, and enjoys the competitive nature of the HVAC industry. “I like that no two days are ever the same as there are always questions to answer and problems to solve,” he says. “Most of all, I enjoy working with great people and coordinating together on challenging projects to achieve positive results together.”

                      Outside of work, Charlie enjoys spending time with his wife, Lesley, and their three boys. He’s also fond of golfing, traveling, and attending concerts and sporting events. One of his favorite quotes is from the book of Philippians: “Do nothing from selfish ambition or conceit, but in humility count other more significant than yourselves. Let each of you look not only to his own interests, but also to the interests of others.” Because HVAC and construction is such a team effort, he says, “this mindset helps to create positive results in a vast majority of situations.”

                      A message from Charlie on the culture of SVL

                      “At SVL, we strive to cultivate a unique culture that revolves around finding and empowering exceptional individuals. We believe in equipping our team members with the right tools and resources to succeed.

                      As we’ve grown the business, we have deliberately maintained a small firm culture, fostering an environment where collaboration thrives. We encourage open dialogue and promote a sense of comfort among our employees, allowing anyone to ask questions and seek guidance from anyone else, regardless of their level within the organization.

                      We foster a workshop-like atmosphere where everyone’s contribution is valued. Presenting your work to another individual or a group of teammates provides a platform for collaboration, where ideas are shared, dissected, and improved collectively. We firmly believe in the power of mentoring and provide various avenues for both formal and informal guidance. Whether it’s through structured training programs or casual conversations, we encourage team members to discuss a wide range of topics, from work-related successes or issues to everyday personal life topics.

                      In summary, our culture is built on the foundation of attracting exceptional individuals, empowering them with the necessary tools, and fostering a collaborative environment where mentorship and growth thrive. We are committed to creating an atmosphere where every team member feels supported, valued, and encouraged to reach their fullest potential.”

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                      Al Gramse

                      Vice President of SVL Service Corporation

                      Al Gramse has been in the HVAC industry for over 30 years. He began as a service technician.  Then over his career worked in technical support, building automation, then service manager prior to his current role.

                      How did Al end up in the HVAC industry?  “After high school, I took a couple years to figure out what I wanted to do.   Where I was working at the time, a grumpy old coworker, who I didn’t get along with, walked up to me and said ‘What are you doing here?  Go back to school.’”  I said, “For what?”  He said “There’s a tech school down the street.  Go down there and pick something that interests you”. Then he walked away.  That weird interaction, with someone I didn’t get along with, sent me down a 30-year path in the HVAC industry.   Never underestimate the potential of a little encouragement.   Even if it is from a strange source.

                      Al has been with SVL for 15 years and is the head of our SVL Service division. “The people here are some of the best in the industry,” Al says. “A bunch of team-oriented, knowledgeable, go-getters.” His personal mantra is “figure it out,” “Do a little fact-finding on your own. Use your own brain before you use someone else’s. But know when to ask for help.” he prescribes. “It’s amazing what you can accomplish on your own if you dig in a little bit.”

                      Outside of work, Al has lots of outdoor hobbies, including hunting, fishing, and motorcycling, though his favorite pastime is simply hanging out with family.

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                      Jennifer Roach

                      Director of Marketing, Events & Administration

                      More than just a creative director, Jen brings 30 years of marketing and leadership magic to SVL. Her journey began in the trenches of graphic design, quickly evolving into crafting eye-catching campaigns for iconic brands like Target, Gabberts, Gander Mountain and Camping World. As a seasoned director and agency veteran, she honed her skills with recreational vehicle giant Parts Unlimited before leading creative teams at HOM Furniture and, ultimately, landing at SVL during a crucial growth phase.

                      Jen thrives on "servant-leadership," empowering her team and fostering a culture of trust and mutual respect. "It unlocks their potential, fuels creativity, and leads to work we're all proud of," she says. "I want my team to care, collaborate, and push boundaries together."

                      When not shaping impactful campaigns, Jen enjoys weekend adventures with her husband, Scott, and son, Crew. Their lives are a tapestry of shared passions, from bike rides and baking experiments to cheering on Simley High School wrestlers. And with her recently built forever home in Cottage Grove, her free time now includes a new, thrilling chapter: weekend renovation warrior!

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                      Mike Ruff

                      Vice President of Information Technology

                      Mike Ruff, the Vice President of Information Technology at SVL Inc., is a seasoned professional with an impressive 24-year tenure in the IT industry. His journey in the field is marked by extensive experience and expertise in various domains, including serving as a Cloud Architect focusing on Azure Software as a Service (SaaS), Infrastructure as a Service (IaaS), and both B2B and B2C solutions. Mike’s skills extend to being a Security Architect, where he has honed his knowledge in safeguarding digital assets, and he is also proficient in the Microsoft 365 stack, virtualization, routing, switching, and wireless technologies.

                      Beyond his professional roles, Mike is deeply passionate about technology in all its forms, which is evident in his career and personal hobbies. His love for technology is not just limited to his work but also spills over into his leisure activities. In the summertime, Mike enjoys the thrill of riding his motorcycle, embracing the freedom and adventure it brings. When winter arrives, he switches gears to snowboarding, seeking the excitement and challenge of the snowy slopes. These hobbies reflect Mike’s dynamic personality and continuous pursuit of technically engaging and physically exhilarating activities.

                      Mike Ruff's blend of professional expertise and personal passions make him a unique and valuable asset to SVL Inc., embodying a perfect synergy of technical acumen and a zest for life's adventurous aspects.

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