Bottom Lines for Balancing Valves in Recirc Systems
By Jim Allen, CPD, LEED AP BD+C, Director of Plumbing Engineering, Jordan & Skala Engineers, Inc.
Balancing valves in recirculation systems does what Marsha Brady’s hair brush did for her long “hair of gold.” It smooths out unruly, turbulent, and unequally demanding branch circuits to make uniform flows in the system. When installed properly, your hot water system will work as well as Marsha’s hair looked when she met Davy Jones. Groovy! Following are five tips on balancing valve design.
Keep it simple and have the big picture in mind
As engineers and designers, our job is No. 1 to figure out how to make things work. No. 2 is communicating to others how to make what we design. No. 2 is just as important as No. 1, or maybe more important. In order for No. 1 to work, there must be No. 2!
In our designs, we like to take the most complicated systems and reduce them down to the lowest common denominators. By keeping the systems as simple as we can, we can better communicate in our designs how the system is to be installed. Bottom line: Keep it as simple as you can!
Know the role of the balancing valve
I coach a 13u travel baseball team. The team is comprised of a group of middle school boys in various stages of puberty. Three of the boys are full grown men at this point, and I fear for my life when I pitch to them in the batting cage. Three other kids on the team are still waiting for their hormones to kick in and are still small, but super fast. The others are in various sizes and stages of puberty. Heck, one kid only has hair under one armpit!
It’s my job, as a coach, to take all these various kids and balance them into a team that works efficiently. Balancing the small with the large is an exciting task, to say the least. The balancing valves job is very much the same, in that it is taking varying demand hot water return lines and smoothing out the flow to achieve a uniform and equal flow back to the water heating source so that larger branches don’t choke out the smaller branches. Using the balancing valve increases system efficiency and saves energy and water. Bottom line: Know what role balancing valves play in your hot water system.
Designing the ‘perfect’ system
Sometimes, as designers, we get lost in our calculations and require the balance in flow to be absolutely equal in all branches. In some of our past projects at Jordan Skala, we demanded that balancing valves in hotels be set at ½ gpm. It worked GREAT on paper and made us feel great about ourselves that our design was this tight. In reality, the contractors could not get the systems to balance properly at those low flows.
So, we had to listen to what was achievable in reality and modify our designs to show 1 gpm flows, which was much easier to obtain in the field. Understand that balancing valves help increase efficiency of the system and save water, but build some “cushion” into your design to allow for system adjustments. Bottom line: Make sure your design is realistic and build-able.
Ball valves are not balancing valves
Balancing valves are ball valves or gate valves, but ball valves and gate valves are NOT balancing valves. Use the right tool for the job. Sometimes, the installer will take it upon themselves to VE the job and use ball valves in lieu of balancing valves. This is like herding cats…it just does not work and you will never achieve the balance in the recirc system that it requires.
Balancing valves are calibrated to allow certain flows through them with set points and scales built in to let all know what the valve is set for in the system. With a typical ball or gate valve you’ve gone all Bon Jovi, “Livin’ on a Prayer!” Additionally, once balanced, you can remove the “adjuster” to keep uninformed maintenance staff from finding a valve not “all the way open” and opening the valve wide open.
Bottom line: Never accept less on components that are system-critical.
Much like the invention of the variable speed pump, the introduction of the pressure independent balancing valve has covered a multitude of sins. In complicated, multiple pressure zones, such as high-rise buildings or long, spread out buildings, the pressure independent balancing valves help make your job as a designer easier. The valves still control flow without the worry of pressure differentials.
You still need to be aware of the limitations of these valves, but they can aid a designer and contractor with a larger margin for error.
Bottom line: Embrace the technology!