ASHRAE Journal - September 2009 - 11

The Case Against Balancing Valves Author Response We have heard these comments from Mark Hegberg before. He broadbrushes the math but does not contest the article by referring to a specific detail or calculation. I firmly disagree that the system head curves are in error. We also have seen his valve authority figures before. If you design a modulating valve with adequate shut-off capability (200 psig), size it via the CV method, and give it plenty of range (200:1), you need not worry about how the valve fits with coil losses or whether there will be excess flow at any point in the rangeability. With coil control valves conforming to these specifications, we are seeing temperature differences of 14°F to 20°F on systems designed for 12°F. Can you imagine the energy savings? This letter doesn’t bother us, but we take offense to Mark’s remarks about ASHRAE Journal’s article reviewers. They are doing a tough job without compensation; they find numerous errors and always make an article better. Both of us have been in the design of hydronic systems using variable primary pumping without balance valves for farthest circuit should only be adjusted for the coil loss and no other reason. From the pump and system curve graphs, it becomes obvious that there is significant “constant flow” savings attributed to the proper use of the balance valve, not the improper use the authors contend to be correct. The authors are quite wrong. The authors are also wrong in their statement, “The calculation of the energy consumption for the constant flow systems is simple since the pump always operates at one point, 360 gpm (23 L/s) at 73.5 ft (220 kPa) head for the system….” Again, the calculations for control valve authority prove, with no doubt, that a three-way valve is not constant, and operSeptember 2009 the past 15 years. There are thousands designed by HVAC engineers without balance valves in use. These systems have saved millions and millions of kW over what would have been expended if balance valves had been incorporated. James b. (burt) Rishel, P.E., Life Member asHRaE, cincinnati Author Response Thank you, Mr. Hegberg, for taking the time to list your debate points. It would have been proper for you to include a statement such as: I am associated with a balancing valve producer, so my opinions may not be objective. Please keep this in mind as you read my letter. We will continue to encourage our clients to design systems with highquality, pressure-dependent control valves and no balance valves. The only thing pressure-independent control valves and balance valves do in an all variable flow system is to increase the water transport (pumping) energy for the life of the building. gil avery, P.E., Life Member asHRaE, cordova, Tenn. ates at their stated design point when the valve is either at 0% or 100% stroke only. Note, that I analyzed this system using real selection data. The authors would have us believe that the coil and valve would only be 10 ft head loss, making the actual results worse than what I have presented. But three-way valves are known energy wasters and should not be used. Using the “constant”-flow system as the basis of comparison, the authors then take their thin thesis a step forward and compare balancing valves to a variable-speed, variable flow system. That’s like comparing apples and oranges. In that regard, they further attempt to mislead the reader by making comSee Case for, Page 13 www.info.hotims.com/25208-19 ASHRAE Journal 11

ASHRAE Journal - September 2009

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