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Flow Instrumentation

Badger Meter Improves Operating Reliability in Hydronic Heating and Cooling Applications

Recordall® Disc Series meters detect low-flow water leak rates as part of a hydronic closed system makeup assembly

Hydronic heating and cooling systems not only ensure a building’s energy efficiency but also reduce costs and increase sustainability. New developments are changing the world of hydronics, permitting commercial heating, ventilation and air conditioning (HVAC) installations that meet stringent energy efficiency requirements and automatically integrate with other building systems.

Users of hydronic equipment may think they don’t have to worry about water or coolant losses in closed-loop systems. However, even the smallest losses can have significant ramifications if unaddressed—which is why it’s important to locate the source of any leak.

Hydronic system operators can uncover their closed system leaks through the use of nutating disc water meter technology. Leak detection can be accomplished by installing these robust devices within cold water and glycol makeup assemblies.

Challenges for Building Owners

Building owners/operators are seeking to deploy advanced technology to obtain high performance from their HVAC systems. These assets play a key role in the efficient operation of large commercial and industrial facilities.

All closed loop hydronic heating and cooling systems are filled with water or a mixture of water and antifreeze. The only intentional air in the system is contained in the expansion tank.

The automatic cold water or glycol makeup assembly in a hydronic system is critical to avoiding the introduction of unwanted air and maintaining proper pressure in closed systems. A pressure reducing valve (PRV) is used to replenish any lost water in the system, but with this water comes oxygen that can pose challenges ranging from the build-up of rust or particulates to damage caused by mineral interaction with metals and elastomers and other conditions.

In closed systems, most water is made up due to isolated events, such as service of a product or removal of air. Occasionally, water is introduced due to a small leak somewhere in the system. This leak can be so small that the issue is hidden from the building owner or contractor.

Need for Leak Detection

Experience has shown that hidden, slow leaks of water from underground piping, air handling unit (AHU) coils and equipment in unoccupied spaces can cost a lot of money over time in hydronic systems. If they are making up additional water, it is important to determine the source of the leak before operating costs escalate and an unexpected system failure occurs.

In a closed water system with an 1,800-gallon capacity, experiencing a 1/16th gallon-per-minute (GPM) undetected leak, it would only take 21 days until all of the original water in the system was replaced by make-up water. With a ¼ GPM leak, the time for full water make-up replenishment drops to five days. This is a waste of valuable resources and accounts for the added cost of replacement chemicals.

In a closed glycol system experiencing a leak, with freeze protection starting a -10° Fahrenheit and water makeup, the safeguards on system assets will be all but gone within a matter of days.

Importance of Flow Metering

Flow measurement technology is a valuable tool for closed hydronic system optimization and troubleshooting. Flow meters measure the rate of flow of a fluid moving past a certain point within a specific system, such as water moving through a pipe.

For HVAC-related applications, the flow measurement device should be of industrial quality and capable of reading very low flows as well as accurately sensing total system design flow. Users can install a flow meter on the makeup water line to a closed-loop hydronic system to determine if there is an increased requirement for makeup water without performing chemical residual checks.

When it comes to hydronic system flow metering applications, one of several approaches is normally taken. The first method uses displacement, while the second most common option focuses on velocity. Other methods that can be used include electromagnetic and ultrasonic.

A displacement water meter is one of the variants most commonly used in closed hydronic system applications. These meters, also referred to as positive displacement meters, can be divided into two subcategories: oscillating piston and nutating disc meters. Regardless of the specific design, each displacement water meter measures the rate of flow based on the movement of a specific element within the meter’s construction. The amount of movement recorded correlates to the amount of water that has entered through that portion of the system. The water meter is less concerned about the rate of flow than the volume passed through it.

Choosing the Right Solution

For commercial and industrial building operators choosing flow and energy measurement products for their hydronic systems, the typical selection criteria includes:

  • Accuracy requirements
  • Installation environment
  • Output requirements
  • Interconnectivity needs
  • Maintenance and serviceability considerations
  • Budget limitations
 

Recordall┬« Disc Series MetersR. L. Deppmann, a leading manufacturer representative supplying HVAC and plumbing systems to customers in Michigan and Northern Ohio, found a solution for hydronic leak detection that is simple and cost-effective for facilities of all sizes. The company has successfully deployed Recordall® Disc Series meters from Badger Meter to measure the low-flow conditions commonly found in closed system applications. These meters employ a patented measurement technique combining the accuracy of a positive displacement design with the reliability and economy of nutating disc technology.

As part of the nutating disc metering principle, water flows through a strainer and into a measuring chamber where it causes the meter’s disc to nutate. The disc, which moves freely, nutates on its own ball, guided by a thrust roller. A drive magnet transmits the motion of the disc to a follower magnet located within the permanently sealed register. The follower magnet is connected to the register gear train. The gear train reduces the disc nutations into volume totalization units, which can be displayed in gallons for local readout or provided as a 4-20 mA or pulse output for remote monitoring.

Advantages for End Users

The easiest way to check for leaks in closed hydronic heating and cooling systems is to read and record the water usage displayed by a totalizing water meter on the makeup water line.

Although the accuracy of nutating disc water meters drops off at flows below ¼ to ½ GPM in this application, they are capable of sensing much smaller flow rates and can be used to detect miniscule leakage in closed-loop environments. They can also produce output pulses when water flows in the reverse of the usual direction in systems. This reverse flow would indicate the usage of the backflow preventor safety device.

In the case of the Recordall Disc Series meter, proprietary technology provides flow accuracy of 1.5 percent from 1/2…20 GPM. Below this range, the meter is capable of measuring water leaks down to a rate of 1/32th GPM. By comparison, at 1/16th GPM, many other meter technologies lose a significant degree of accuracy or are unable to measure any flow at all. This is a key advantage for hydronic closed system applications, which are characterized by exceptionally low water leak rates. The device’s low pressure loss also results in an ideal long-term metering solution.

In addition, the Recordall Disc Series meter’s reduced disc nutation rate decreases chamber wear and extends long-term accuracy. To simplify maintenance, the register, measuring chamber and strainer can be replaced without removing the meter housing from the installation.

The Recordall Disc Series meter’s low-lead bronze valve body complies with the lead-free provisions of the Safe Drinking Water Act and is certified to NSF/ANSI Standards 61 and 372. It also exceeds the AWWA C700 and C710 standards for the use of cold water displacement meters with bronze main cases.

Most importantly, this solution provides simple and affordable insurance for building owners/operators concerned with protecting the health of their hydronic system assets. Water meter outputs can be supplied to a building management system (BMS), so personnel are alerted of leaks causing the loss of valuable resources, high chemical replacement costs and severe equipment damage. The BMS for alerting option for unexpected water use eliminates the need to manually read the meter with valuable maintenance labor hours

Conclusion

Identifying leaks in hydronic closed systems is critical to reducing the overall cost of commercial/industrial building operation, while maintaining the superior performance desired.

Facility owners with hydronic system leak detection applications can realize numerous advantages by implementing closed system makeup water meters based on advanced nutating disc technology. These devices have proven to be an accurate, reliable and cost-effective tool for long-term monitoring of very low water leak flow rates.


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