ENERGY SAVING
2: Pumps operating outside their natural curve
Perhaps the most important technical issue to address is the choice of control strategy. Capacity-based control focuses on the equipment being at its most effi cient when operating at 100% design fl ow. In reality, however, the system will operate at between 10% and 60% of design fl ow nearly all of the time. So, demand-based control improves effi ciency by focusing on meeting the actual load most eff ectively. Pumps incorporating Sensorless control have signifi cant advantages in delivering demand-based control, as they automatically adjust to changing demand whilst reducing system complexity. When a variable frequency drive is added to an HVAC component, such as a pump or fan, there is enormous potential to improve part-load effi ciency due to the pump affi nity laws (change in power is proportional to the change in rotary speed cubed: (P � N³). If a rotating device is allowed the fl exibility to operate along its peak effi ciency natural curve, this can increase operating effi ciency by 400%. These effi ciency improvements can only be achieved, however, if the pump affi nity law relationship between pressure and rotary speed, along the natural curve, is maintained at decreased speeds. The latest generation of intelligent pumps incorporates
on-board inverters, making them capable of automatically adjusting to changes in load. Design point and setpoints can be adjusted to match on-site conditions, and the pumps are sequenced to operate along their peak effi ciency natural curve automatically, for all load conditions. Equipment loading can be optimised across the system as a whole to achieve signifi cant reductions in energy consumption.
3: Ineffi cient staging of pumps As well as ensuring the effi ciency of each pump, it’s essential to make sure the control methodology is in place to eff ectively balance the diff erent pumps against each other, managing the entire plant room in the most effi cient way possible. The latest generation of control technologies can optimise energy effi ciency by phasing components such as pumps and boilers in and out more eff ectively as demand on the system rises and falls. Traditional pump staging strategies, for example, turn on the next pump when the existing or current pumps reach 95% of maximum speed. Pumps are typically staged off when the existing or current pumps slow down to 55% of maximum speed. Both of these scenarios (staging pumps on too late and off too early) involve lost effi ciency. The best practice alternative is to adopt effi ciency-based staging points (as opposed to staging points based on pump speed). With this control strategy in place, the system ‘surfs’
across the top of the effi ciency curves throughout the day, eliminating the wastage inherent in pump speed-based control approaches. This improved strategy can achieve energy savings of over 30%.
Number 4 - Operational drift Throughout the lifetime of the pump, ineffi ciencies such as operational drift can develop over time, perhaps as a result of adaptations to the system after installation of the pump, which undermine its performance. These issues can now be
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overcome easily, however, by utilising recent advancements in cloud computing and machine learning. Today’s pumps provide far greater connectivity and allow the user or custodian to keep up to date with real-time monitoring on browsers or apps. The ability to monitor pump performance in real-time is extremely valuable for reducing energy costs, improving environmental performance, and predicting potential technical issues at any stage in the lifecycle of a building. This level of Active Performance Management, for example, is available from Design Envelope pumps with the use of Pump Manager. This is a cloud-based service that provides smart analytics, diagnostics, and alerts to support HVAC system effi ciency. With Active Performance Management, operational drift can be identifi ed and rectifi ed early to ensure that energy effi ciency does not deteriorate over time. It’s important to remember that improving effi ciency does not always involve replacing the complete pump. Many Armstrong pump models, for example, are designed to enable the pump head/rotating assembly to be updated whilst leaving the pump body in place. This reduces cost and disruption for the upgrade of the pump and can unlock signifi cant savings. In conclusion, there are various stages throughout the lifetime of a pump when rapid, eff ective action can be taken, to avoid building ineffi ciency into a design from the outset, to optimise the system throughout its working life, and to detect and remedy operational drift.
'The latest generation of pump models is inherently more effi cient than its
predecessors. The latest motors don’t just meet effi ciency standards; they outpace them entirely.'
www.acr-news.com • January 2026 19
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