Finance’s Lisa Garcia Goes Above and Beyond

Here’s to IMI Hydronic North America’s Lisa Garcia, AP Staff Accountant and July’s winner of IMI’s Above and Beyond award. This company-wide honor recognizes employee excellence, teamwork and performance that exceeds job expectations.

In her nomination, Becky Man, Financial Director for the Americas, noted Lisa’s above-and-beyond work during the annual inventory at IMI Hydronic’s North American headquarters in Dallas. “Lisa virtually ran the inventory for Finance single-handedly, putting in considerable additional hours and dealing with several difficult situations both professionally and calmly.”

Thank you and congratulations Lisa Garcia!

Video Challenge Series: Get to Know Julie Coronado

With social distancing keeping us apart, we challenged the IMI Hydronic team to connect with customers through video that shares their favorite activities and IMI products. 

The series continues with Julie Coronado, Customer Support Supervisor at IMI Hydronic North America, who enjoys the outdoors, especially walking her dog. Just like walking is central to Julie’s exercise routine, the AutoFlow Cartridge, her favorite IMI product, is the heart of every AutoFlow Valve from IM Flow Design. With a patented hybrid port, the ½” AutoFlow Cartridge can control rates as low as 0.5 gpm with precision.

Watch Julie’s video, then, go to to learn about our full line of AutoFlow Valves. Or connect with, or to find out more about designing with them for your hydronic balancing system.


Valve Authority

So, what is authority? Intuitively, we can imagine a circuit with a pump, a small restriction, and a large valve with which we intend to control the flow. When we throttle the large valve almost nothing happens when it is near the open position, then the flow changes suddenly near the closed position. The valve is said to have poor authority because most of the time something else is controlling the flow.

The problem with low authority in a control valve is that it produces unstable operation during low-load conditions (ASHRAE 2020, 46.9). Thinking about the valve in the situation above, if we intend to set a precise flow rate it might not happen because a small tap to the handle sends the flow above the target and a tap in the other direction sends it below.

The basic definition of authority is (Petitjean 1994, 146):

Some sources use the version (ASHRAE 2020, 46.8):

In hydronic systems, though, the actual variable of interest is the heat transfer of the terminal which saturates with increasing water flow if all else stays the same (Figure 1). This leads to a definition of "Practical Valve Authority" denoted by β':

Here the numerator is the pressure drop of the control valve at nominal flow when fully open, or approximately ((Design Flow)/Cv)2

Figure 1

As a result of terminal saturation, even though the shape of the flow curve might be the same at higher pressure, the fact that it is scaled up means that the shape of the heat transfer curve (heat transfer vs stroke) is not the same at different pressures. As already alluded to, the trouble of low authority shows up as unstable control at low flows. The two curves in Figure 2 have the same resistances within the branch but different differential pressures across the branch. As can be seen, the slope of the higher-pressure curve is about twice that of the lower pressure curve in the neighborhood of the closed position. In Figure 7 we see a comparison for the same pressure as the orange trace in Figure 6, with either no balancing, manual balancing, or a flow limiter. It's important to note that this is the comparison with a pressure that would cause 2x overflow at the fully open position of the control valve without balancing, and thus it's a fairly large pressure being absorbed by the balancing device (for instance if the nominal flow was at 10 psi, this figure would be at 40 psi so the balancing devices would be absorbing 30 psi at the open position). While the curves are not identical, they all have the same maximum slope near the closed position. The curves in Figure 3 all have the same practical authority β' as defined earlier, but different values of β according to the definition that ignores the target flow rate.

Figure 2: Same β, different β'

Figure 3: Same β', different β

Figure 4: After turndown

Clearly from figures 2 and 3, β' is a better indication of authority for a hydronic terminal. In Figure 4 we see the same set of balancing situations as figure 3, but at the pressure represented by the blue curve in Figure 2. Once again, the slopes of the curves all converge in the neighborhood of zero showing that β' is a better indication of authority for a hydronic terminal.

Customer Service Team Goes Above and Beyond





Here’s to the IMI Hydronic North America Customer Service team, June’s winner of the Above and Beyond award. This company-wide honor recognizes employee excellence, teamwork and performance that exceeds job expectations.


In his nomination, Chris Rodgers, Vice President of Sales & Marketing for IMI Hydronic Americas, noted the team’s overall dedication, working to improve department performance while supporting IMI Flow Design during a global pandemic. “You put in long hours,” he wrote, “along with extra hours working for other departments hit hard by illness and a perfect storm of stressful circumstances.


“You brought smiles to the faces of our customers,” Chris continued. “They noticed. I noticed.”


Congratulations Jenna Bauer, Julie Coronado, Marci Simmons, Shonte Webb!


Video Challenge Series: Get to Know Shonte Webb

With social distancing keeping us apart, we challenged IMI Hydronic team members to connect with our reps and their customers through video by sharing their favorite activities and IMI products.

We continue the series, with Shonte Webb, a 21-year Customer Service veteran who enjoys reading a good book. Just like books open up new possibilities for Shonte, she appreciates the lead-free, NSF/ANSI 61-G certified ICSS automatic control valve that unlocks opportunities for customers in their commercial hot water contact applications. Our ICSS lead-free valves meet the industry’s latest lead content standard, established by the Reduction of Lead in Drinking Water Act (RLDWA) in 2014.

Take a look at Shone’s video, then go to for more information about IMI Flow Design’s Domestic Water (Lead-Free) ICSS Balancing Valves. And to learn how to design them in domestic hot water circulation systems, contact Armando Reyes at, Hailey Mick at or Rich Eberle at Or email us at