HYDRONICS
The hydronic balancing act HYDRONIC BALANCING
BY BOB “HOT ROD”ROHR CONTRIBUTING WRITER C 70
ertainly we need balance in our daily lives. Finding balance between work and play can be a quest, especially for small shop, self-employed owners.
Of course, a positive balance in our bank accounts is a good thing to strive for, too. Let’s talk a bit about balance in a hydronic system.
Balancing is often overlooked in hydronic systems. Many residential hydronic systems are installed without a means to balance or even confirm flow rates. Balancing is important if you want to get the highest performance, best efficiency and ultimate heat transfer. In larger commercial system design, you will always find
balancing devices in the spec sheet and mechanical drawings. A specialty contractor is often employed specifically to balance and adjust the system at startup to assure optimum performance. But what about the smaller, installer-designed hydronic
systems? Without a doubt, all systems would benefit from proper and complete balancing. The good news is that there are more and more components on the market to assist even small shops in balancing. Many radiant and hydronic manifolds offer loop balance options. In addition to an adjustable valve, these manifolds are also available with flow indicators. With some brands of manifolds, you can turn the small flow indicator to adjust the attached balancing valve below it. So now you can “dial in” every loop connected to the manifold to the design flow rate. If you add a couple of snap-on temperature gauges, you now have the ability to determine the Btu output of every loop. This can be a handy troubleshooting procedure. The formula is fairly simple: Supply temperature - return temperature 5 flow rate 5 500 (factor for water.) An example of a radiant loop with a 10-degree temperature drop would be (110 - 100 F) 5 2 gpm 5 500 = 10,000 Btu/hr. Some other applications that may require
balancing components are solar and GEO installations. If a large solar thermal array is
In larger commercial
system design, you will always find balancing devices in the spec sheet and mechanical drawings. Often times a specialty contractor is employed specifically to balance and adjust the system at start up to assure optimum performance.
installed with multiple banks of collectors, a flow balance valve should be installed to assure that every group of collectors is receiving adequate flow. Only with a balancing device will you be assured of peak performance. You will notice all of the pre-plumbed, packaged solar pump stations come equipped with flow setters. These are typically a spinning plastic flow indicator with a basic ball valve for adjustments. The same balancing principles apply to the loop field
installed with a ground source system. Without flow balancing and flow indication, how will you know what each loop is contributing to the load? Balancing the loops could be accomplished with a quick-setter installed on every loop at the manifold. With a pump and dump type of geo installation, a balance valve would be installed to set the appropriate flow rate through the heat exchanger. Balancing devices are offered in a large array of types and
sizes. There are a few types of ball or disc valve balancers that have a quick-set feature. With these components, you pull a ring to view the flow and use a small wrench to adjust the flow. The quicksetter type of valves do not require an additional differential meter to check and adjust. The well known Bell & Gossett Thermoflow and Caleffi QuickSetter are a couple of examples of this type of setter/ indicator. A more refined type of flow adjusting valve uses a
tapered cone or plug to provide finer and more accurate adjustment across the range. These are referred to as equal percentage valves. A step up in accuracy would be a valve with an equal proportion valve mechanism. This type would have a cone-shaped valve mechanism to provide better adjustability. A PIBV (pressure independent balance valve) is a type of
automatic balance valve that will maintain a set flow even as the system pressure changes. This type of valve is commonly installed at air handlers in multi-unit building applications. So, as the various air handlers come online and go offline, the PIBV will assure the exact flow is being supplied. In some cases, a manual balance valve could be installed on a riser feeding one floor of a multiple story building. In conjunction with the riser balancer, the PIBV would be installed at the heat emitter. Most balance valves will have a means to test and adjust
the flow rate. Often a couple of PT (pressure/ temperature) ports are provided. A differential pressure gauge will be connected to the two ports to read the flow rate. Use a delta P circulator in the system with a balance
valve, and you will get the best performance and efficiency. The flow valve “nails” the desired flow rate and the pump modulates it’s output to match the system load. The delta P circulator will consume less energy as it reduces its output as zones close down. That’s a lot of technical talk. Let’s balance that with the
benefits of balancing; more efficient, more comfortable and less problematic hydronic systems. l
phc december 2011
www.phcnews.com
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