Ultrasonic Meters Improve Hydronic System Performance for Large New York City Hospital

As healthcare facilities navigate the rapidly evolving coronavirus pandemic, they must focus on the role hydronic-based heating and cooling plays in the comfort and safety of patients and staff. According to the Center for Disease Control (CDC) and ASHRAE, hospital HVAC systems are key to mitigating the spread of diseases like COVID-19. These systems must perform effectively and reliably on a 24/7 basis— regardless of fluctuating load demand due to changing occupancy levels.

With large central utility plants, hospitals face the challenge of optimizing heating and cooling system performance across patient quarters, operating rooms, intensive care units (ICUs) and other vital areas of their facility. Hydronic components are among the largest consumers of electrical usage in most buildings. Any inefficiencies in their operation can cost tens to hundreds of thousands of dollars annually from wasted energy to unbalanced and stressed equipment, which drastically reduces life expectancy of this valuable asset.

Since facility operators devote a large portion of their budget to processing hot and cold water and distributing it around their facility, they have an urgent need to determine the correct amount of this resource required and to ensure equipment is not overworked and running efficiently to reduce wear and possible failures. Chillers typically account for approximately 35-50% of an entire building’s power consumption, making them the single largest power consumer for most properties. As power costs continue to rise, the need to monitor and maintain chiller health becomes a top priority. While chillers may be providing adequate cooling that is required for the property, the health of this equipment will continue to degrade over time. Not having a precise mechanism to check for chiller and pump efficacy will create a very costly increase in power consumption.

It has been determined that many chillers can lose more than 30% of their capacity and efficiency over time, which can cause an increase in the building power bill by up to 15% without knowing the cause or even realizing this added cost could have been prevented. Even when preventive maintenance programs have been in place, many things can go unnoticed without flow or energy measurement tools in place. Installing these devices will precisely show inefficiencies such as flow rate deviations, delta temperature changes and British Thermal Unit (BTU) energy output changes that directly affect the chillers’ efficiency and allow facility owners to quickly identify issues and make the necessary modifications to bring chiller performance back to its design levels.

Typical Operating Challenges

Many hospital chiller and condenser systems are working far below peak efficiency, often due to flawed system design or poor operations and maintenance practices. This situation results in high energy costs, limited reliability and short equipment life.

Hospital personnel often complain about "hot spots," especially in areas farthest from the central utility plant. Health care facilities also face significant increases in energy costs due to higher gas costs as well as rising transmission and distribution costs.

Maximum chiller efficiency is achieved by controlling refrigerant flow and getting the coldest possible water to condensers. This cold water is produced at cooling towers, which makes the operation and maintenance of the units critical to maximizing overall system performance.

A large New York City hospital required a solution to ensure the reliability and efficiency of its HVAC hydronic system operations. The hospital’s facility engineering department hired a leading controls contractor to provide instrumentation to measure chilled water and condenser water flow as part of HVAC system monitoring by the hospital’s new building management system (BMS). Engineers wanted to obtain energy data for the chilled water produced by chillers in their mechanical room as well as gather information on the condenser water used to remove heat from refrigerant pumped to rooftop evaporators.

The hospital needed to get flow measurement data in the most economical way possible without sacrificing accuracy. In a new building, inline electromagnetic flow meters are typically recommended because they offer excellent accuracy. But since this was an existing facility, and because in-line devices such as magnetic flow meters are intrusive, the hospital’s chiller system would have to be shut down and pipes cut to install the meters. Even insertion technology requires a substantial investment with welding, drilling and hot tapping instruments into the stream of flow with possibilities of pipe shavings entering the piping system, which could cause significant damage to pump blades and equipment within the hydronic piping system. Facility engineers did not want welding and drilling taking place in their mechanical room, and the time involved in welding and hot taping insertion meters was unacceptable. They required flow measurement equipment that could be up and running quickly and installed while the system was in operation.

Importance of Flow Measurement

Hydronic HVAC systems have rigorous operating demands and strict flow measurement requirements that large facilities must meet. Installing efficient hydronic heating and cooling components is an important step, but flow instrumentation is essential to maintaining long-term accuracy, reliability and repeatability within chillers, chilled water systems, cooling towers, condensers and other asset operations.

Measurement of chilled water flow and thermal energy/BTUs is essential to determining the amount of heat transferred between the cold and hot flow legs of a hydronic system process. When there is only a small difference in temperature between the two flow legs, a precise measurement makes a huge difference.

However, many facilities struggle to achieve hot and chilled water system flow rate measurements that are accurate, low cost and non-disruptive. Building operators require versatile flow metering solutions to maintain the delicate balance between low cooling system energy consumption and capital investments.

Chilled water applications typically involve the conversion of flow rate/supply and temperature data into BTU or tonnage (TONN) usage to show operators when a chiller load reaches 40% or lower, indicating it is time to stage down a chiller. When a load reaches 60% or higher, it is time to turn on another chiller to reduce system load.

In condenser applications, it is important to maintain good quality boiler supply water and remove low-quality water by measuring boiler feed/blowdown and condensate return flow on a volumetric basis.

In the case of the New York City hospital, facility engineers sought to obtain accurate measurements for both flow and energy in their hydronic HVAC system. They wanted a device that would be as close to inline measurement as possible without the high installation costs and downtime involved with this technology. The engineering staff disregarded insertion instruments that would only sample a small portion of the flow profile due to the wide range of pipe diameters in their system. Moreover, they did not want a flow meter that only inserts into one point of measurement, which would not allow for the determination of the average flow velocity through the piping and could cause large errors in the flow and energy calculations. The engineers understood how the Dynasonics^® TFX-5000 transit time flow meter samples the entire cross-sectional area of the piping not once, but twice, with a standard V-mount configuration, providing a true average velocity flow profile for accurate and stable readings.

Selecting the Right Meter

End users involved with commercial and industrial facilities have a wide choice of flow and energy measurement products for their hydronic HVAC systems. The typical flow meter selection criteria includes:

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

A growing number of facility operators are choosing to install ultrasonic transit time flow meters for hydronic HVAC applications. With this technology, ultrasonic waves transmit upstream and downstream through the pipe wall and the liquid flowing in the pipe. By measuring the difference in the travel time and knowing the pipe size, the meter determines the velocity and flow rate.

A clamp-on ultrasonic flow meter is ideal for use with hydronic components since it eliminates the need to alter process piping and can be installed in a fraction of the time required for traditional inline and insertion devices. Designed to attach to the outside of pipes using standard silicone for a hard rubber connection to the line without losing connectivity over time, this type of non-invasive meter does not contact the internal liquid, allowing for installation without shutting down the operation. Hot tap in-field drilling and welding are not required when installing the device. In addition, there is no pressure drop through the meter as there would be with other technologies and no O-rings or seals to maintain. Unlike Doppler-type ultrasonic meters requiring large particles or bubbles in the flow path to read a flow rate, a transit time measurement device provides an accurate and reliable output without modifying cooling water flow.

Technical Air, a qualified HVAC representative for Badger Meter, worked with the controls contractor and facility engineers at the New York City hospital to implement the latest non-intrusive flow and energy measurement technology, which would reduce installation costs and speed up project handoff. The decision to install a TFX-5000 ultrasonic clamp-on flow meter from Badger Meter allowed the entire installation to be completed and commissioned with chillers remaining in full operation. Furthermore, the clamp-on flow meters could be installed by a single technician in accordance with current social distancing guidelines.

The TFX-5000 ultrasonic clamp-on flow meter provided the hospital with a complete flow and energy measurement solution from one instrument, eliminating the need to add a separate BTU monitor to existing flow meters like other solutions. The TFX-5000 meter enables users to obtain flow and energy data out of a single, non-intrusive device. This capability is beneficial for monitoring chiller performance and capacity as well as measuring the refrigerant temperature at cooling towers to avoid system failures. Users can also choose from a wide output offering, including BACnet MS/TP, Modbus RTU, BACnet/IP, Modbus TCP and others.

Facility operators have found that ultrasonic clamp-on flow meters like the TFX-5000 meter serve as a valuable measurement and diagnostic tool for both chilled water and condenser water and refrigerant loops in hydronic HVAC systems. For example, the meters can be installed at any point on water distribution lines to help balance the chilled water process, ensure pumps are not overworked and verify chiller performance under rigorous operating conditions. The meters also help operators maintain refrigerant in heating/cooling coils at the proper temperature. The current fluctuating occupancy level at hospitals demands optimal HVAC system performance to maintain adequate heating and cooling. The days of using differential pressure sensors across chiller pumps to get an idea of flow rate are largely over due to the constant recalibration and inaccuracies this older technology requires.

The ultrasonic transit time flow meters measure the water temperature on both the inlet and outlet sides of a chiller based on established setpoints to ensure the temperature differential does not become too wide. Using measurements taken at various locations along the heating or cooling loop, facility engineers can verify that thermal energy is distributed properly. When this is the case, they can reduce their hot and chilled water production—saving energy and operating costs—and minimize the need for additional maintenance and/or equipment.

A key feature of the TFX-5000 meter for energy monitoring is its high-capacity data logger with eight gigabytes of data storage. The meter offers microSD card data storage and does not require software or download cables. Employing built-in data logging and a real-time clock, this advanced instrument records flow rate, total and diagnostic information with a time/date stamp, thus providing the baseline and load profile information needed to optimize equipment operating efficiency. Its large volume backup data storage can be used for troubleshooting or reporting purposes.

Most importantly, implementation of the TFX-5000 meter as a non-invasive clamp-on design enabled hospital engineering staff to eliminate the costly hot tap procedures of drilling and welding into piping while their chiller system was running. The use of a hot tap during installation could have caused metal pipe shavings to enter the piping and chiller pump system, resulting in irreversible damage to the chiller and condenser pumps.

Benefits to Facility Operators

Experience has shown that ultrasonic transit time clamp-on flow meters are valuable tools for helping building operators measure and manage their hydronic HVAC system performance in a number of ways. These units provide the baseline and load profile information needed to effectively optimize system efficiency and reduce energy consumption and costs.

These benefits are particularly important in times of increased global health concerns, when hospitals and other healthcare facilities are dealing with rapidly changing patient numbers and the subsequent higher loads on their HVAC equipment.

For facility engineers at a large New York City hospital, the Dynasonics TFX-5000 ultrasonic flow meter provided an accurate solution for flow and energy measurement without shutting down their hydronic chiller system. These advanced meters offer advantages such as:

• High accuracy transit-time ultrasonic technology
• Single solution for flow and thermal energy/BTU measurement
• Clamp-on sensors using standard silicone with no pipe cutting
• Free SoloCUE^® setup software eliminates the need to touch the keypad
• Real-time liquid density compensation
• Robust system diagnostics

While other flow measurement technologies are also used in HVAC applications, ultrasonic clamp-on flow meters are often an optimal solution due to their external mounting. The meters are especially well-suited for use with existing hot or chilled water distribution lines, where they are quick, easy and less expensive to install than other flow meter options since there is no need to cut the line, interrupt service or drain the pipe. They do not require the installation of bypass piping and valves for removal, and maintenance expense is minimized since the meters do not have moving parts and, used outside the pipe, do not require periodic cleaning.

Ultrasonic clamp-on flow meters like the TFX-5000 meter are also very versatile in HVAC environments. They can be installed on the full range of hot and chilled water line sizes found in hydronic systems, employed anywhere in the water distribution process, and used to measure two applications simultaneously. These flow meters may be installed where an intrusive meter is not possible or appropriate. All measurements can be logged and time-stamped for creating analyses and reports.

By choosing the TFX-5000 meter, the New York City hospital saved more than $750 per hot tap for 12 measurement points. This eliminated over $9,000 in total installation costs. Deployment of the flow meters was done while the hospital’s chillers were in operation and did not require hot tapping or welding during the installation process.

Last, but not least, the hospital engineering department was able to complete the flow meter project and have balancer confirmation in record time thanks to close cooperation amongst the vendor and end-user stakeholders. Fast project hand-off saved time and money for everyone involved in this successful effort.

Conclusion

There’s no question that chiller and condenser operational effectiveness can greatly impact building operating costs. Predictive maintenance and optimization of these crucial hydronic HVAC system components requires real-time operational data, including accurate information about hot/chilled water loops, BTU tonnage and energy consumption.

A major New York City healthcare facility worked with its instrumentation partners to evaluate various flow measurement technologies and decided the Badger Meter Dynasonics TFX-5000 ultrasonic transit time clamp-on flow meter was the answer to addressing performance, reliability and operating cost issues for its HVAC equipment. This approach has proven to be effective in ensuring hospital occupants are comfortable during difficult times, and the environment for delivering patient care is optimized while keeping important systems in check and running efficiently.