Jul 01, 2020

How Variable Speed Pumps & Pressure Sensors Can Improve Water Systems

This article originally appeared in WQP Commercial Water Summer 2020 issue as "High Rise & High Efficiency"

pressure sensors
Alternative solutions, such as pressure sensors and variable speed pumps, can help improve the efficiency and reliability of water systems in high rise buildings.

For many decades, successfully distributing water on a large scale has been a challenge. Now, combined with the necessity of architects and designers to build up rather than out in many urban areas, the water supply infrastructure has become an integral part of a building’s design. 

In high-rise structures, the occupants—office and factory workers, apartment and condo residents—are all sensitive to failures of the water distribution system. People become upset if their hot water for showers and baths are intermittent or run out because people on other floors use up the available allocation of heated water. 

What happens when hot water does not immediately start flowing? Often, people let the water run until the flow finally heats up, potentially wasting a great deal of water as well as the energy required to pump and distribute the water. In addition, consistent water pressure is a must for correct operations of appliances like dishwashers and laundry machines as well as for industrial and manufacturing machinery.

The challenge to improve the mechanics of building water distribution systems is driven by two fundamental needs: First, the need to increase efficiency, and in doing so, decrease water wastage; and second, to improve the reliability of the installed systems, thereby increasing resident’s satisfaction and reducing the ongoing cost of maintenance and repair.

Traditional Pump Technologies

Older pump technologies in large industrial water systems typically use pressure switches calibrated to switch the pump on if the water pressure falls to below a specific point (for example, below 50 psi) and off if the pressure exceeds a given parameter (for example, 70 psi). This operation is fine up to a point, but it essentially means that the pump is either working at full speed or not at all. These sudden and repetitive surges in demand can lead to problems with reliability and repair. Although undoubtedly rugged, the industrial systems of old also tended to be expensive and inefficient.

New Alternative Solutions

Therefore, pump and water system designers have looked for newer, alternative solutions. First amongst them are the new variable speed pumps (VSPs)

VSPs use a variable frequency drive (VFD) or variable speed drive (VSD) to continuously optimize the pump speed and power consumption while maintaining constant outlet pressure of the pump. In such scenarios, pressure sensors are essential. A pressure sensor measures the outlet pressure and converts the data to an electrical signal which the VFD uses to adjust the pump’s speed. The pressure sensor can be designed as an integral part of the pump design or it can be mounted externally as part of a total solution.

In many cases, a high cut-out pressure switch is also used to prevent the pump from outputting extreme pressure. An additional pressure sensor can also be mounted on the inlet of the pump to monitor efficiency. 

Benefits of Variable Speed Pumps

The benefits of pressure sensors in modern-day VSP design can be categorized into three key areas: efficiency, reliability and the user experience:

  • Reliability—VSPs often run at lower speeds and do not run on a stop/start cycle. Therefore, there is less stress on the pump which results in greater reliability, a longer life cycle and less downtime. This in turn means a lower cost of maintenance.
  • Efficiency—Pumps that utilize VSDs in conjunction with pressure sensors to maintain constant pressure output are proven to be more efficient. Indeed, in tests, they are proven to be up to 30% more efficient than “traditional” technologies (Hydraulic Institute, Europump, & U.S. Department of Energy, 2004).
  • User Experience—The efficiency and reliability of a VSP ultimately translates into an improved customer experience. By using a VSP, even in the more challenging environments such as high-rise buildings, a constant, reliable water pressure can be maintained. Beyond the undoubted benefit of a more reliable water supply, customers are also able to easily modify the pressure supply (depending on load and preference). The digital nature of the technology also allows for greater connectivity with the Internet of Things (IoT), effectively making the pump an intelligent device providing key data that can be acted upon in the event that a problem is identified, such as a burst pipe or leak, or to determine water usage. By using IoT connectivity, building managers can remotely monitor and regulate water use, as well as respond in an emergency by either turning the water systems off to reduce spillage, or by allocating the highest water press to combating emergencies, such as fighting fires on the higher levels of a building. 

Use & Application of Variable Speed Pumps

Traditionally, VSPs have been used in larger, commercial and/or industrial applications, given the previously high costs involved. As costs have come down, and designs improved, notably with the cost and size of electronics in the VFD and VSD, VSPs have become affordable in more mainstream and residential applications. 

This growth has been driven not simply by falling costs but, more importantly, by rising demand. Increasing urbanization on a global scale, often combined with a less than consistent municipal water supply, and power supply mandates, means that the effective delivery of water is a very real challenge. This in turn has prompted the sensor manufacturers to innovate.

It is notoriously difficult to maintain a constant water pressure to every story of a high-rise building, but this is again where the new generation of pumps and sensors come into their own, replacing the inefficient and inconsistent traditional approach to water provision via a rooftop water reservoir. Sensors can detect variations in water pressure to determine when the pump needs to work harder to maintain a constant pressure and when it can relieve the pressure, but without the extremes of being either fully off or fully on. Not only do pumps work more efficiently if they are run at a constant rate, they are also less prone to failure, reducing the associated costs of ongoing repair and maintenance. 

Pressure Sensor Innovation

Sensata offers a range of sensors for use in industrial pumps where components require rugged, industrial housings. For example, its 60/70CP range pressure sensors are proven for use in other industries that require the reliable pumping of liquids, such as oil, and with a high degree of reliability (10 million cycle life-span). They are also robust enough to withstand potentially damaging phenomenon, such as pressure spikes and hydraulic shock.

In addition to the 60/70CP sensors, Sensata has recently launched a cost-efficient pressure sensor family (116CP/126CP), for smaller residential booster pumps. The patented 116CP/126CP sensor design is derived from reliable and proven automotive grade pressure sensing technology. The sensors’ plastic housing has options for use in drinking water applications and makes them ideal for residential and other lower cost pump applications 

The pressure sensor converts the pressure signal into an electronic value, which the pump VFP uses to control or maintain the output pressure. The sensor measurement pressure value is usually presented on the pump’s display, and in some cases, customers can view and monitor pressures via an application on their smartphone or tablet. In addition, a notification can alert users of irregularities and assist in preventative maintenance. 

The world’s water systems are in need of improvement, especially as water resources continue to shrink and become more critical. Many have predicted with the advent of global warming and climate change that access to clean, potable water will be the most critical element of life in the next century. Anything we can do to improve overall water distribution efficiency and reduce waste will be of benefit as the world’s population continues to grow and migrate in response to changing climates and rising ocean levels. 

Manufacturers who are developing and implementing new technologies for water pumps and pressure sensors will play a crucial role in the design of residential and commercial solutions that drive system efficiency and reliability and help to reduce waste while improving the user experience. 

About the author

Daniel Mullen is product line manager for Sensata Technologies. Mullen can be reached at [email protected] or 508.236.3800.

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