How to get an ‘A’ on your building efficiency exam

When we talk about making commercial and institutional buildings more energy efficient, we often mention energy retrofits as the best way to get started. Making small adjustments to your building’s envelope, energy sources or energy flow that can have a big impact on your overall energy usage and carbon footprint. 

The latter aspect – active control of energy flow – is addressed in the new ISO 52120 standard, which is based on the “Energy on demand” approach. The standard defines four different Building Automation and Control Systems (BACS) energy efficiency classes – ranging from D to A – with Class A representing the solutions enabling the highest energy efficiency.  To get a Class A rating, a building must be equipped with a dynamic hydronic balancing solution at the terminal units and modulating room control for both heating and cooling. Not only is making the switch from on/off to modulating actuators a key to getting to the top of the Energy Class, it’s also an example of a relatively small change that can have a big impact on a building’s energy consumption, costs and efficiency. How big an impact? That’s what we wanted to find out.  

Measuring the benefits of modulation 

To answer those questions, we conducted a test at our offices in Trata, Ljubljana, Slovenia. We equipped one office floor with two different hydronic systems: Pressure Independent AB-QM Control Valves with on/off actuators, and AB-QM valves with modulating AME actuators. We ran the test during the summer, where we cooled the office with fan coil units for one month; two weeks using the on/off solution, and two weeks using the modulating solution.  

The difference between the actual and set temperature for the on/off solution was +/- 1° C. With the modulating solution, the difference was only +/- 0.5° C. This translated to a savings of EUR 42 during that period. With the price difference between the two solutions factored in, the payback time for the solution was less than a year.  

Similar results were achieved in a test performed in the laboratory of the Faculty of Mechanical Engineering at the University of Ljubljana. Here the deviation between actual and set temperature was +/- 1.4° C for the on/off solution versus +/- 0.3° C for the modulating solution. This translates to a pump savings of 25.8%; a chiller savings of 6.9% and a temperature control savings of 9% annually. For an average building with 300 fan coil units equipped with PICV valves and modulating actuators instead of thermal on/off actuators, this gives an annual potential savings of approximately EUR 7,800 and a payback time of 1.15 years. 

Fig. 1: Measurements from Laboratory Test 

The graph illustrates the performance of two control methods: On/Off control (left side of the red line) and modulating control (right side of the red line). 

The blue line represents the set temperature, while the orange line shows the actual room temperature. It is evident that the On/Off actuator struggles to maintain a stable temperature around the setpoint. When the set temperature is lowered by 1˚C, the actual temperature decreases accordingly, but the instability persists. 

On the right side of the red line, the graph shows how modulating control performs. In this case, the actual temperature gradually aligns with the set temperature. When the set temperature is raised by 1˚C, the actual temperature similarly adjusts and stabilizes near the setpoint, with minimal fluctuations. 

The grey line represents the room inlet air temperature from the FCU. Under On/Off control, this temperature fluctuates significantly. However, with the switch to modulating control, it stabilizes, mirroring the improved stability of the actual temperature. 

Modulation and temperature stability   

Yet, improving efficiency is only half the equation. Our buildings are more than just empty shells. They’re occupied – filled with people who expect the areas where they work and live to be comfortable. And this is where modulation also comes into the picture. A number of studies as well as our experience of working with heating and cooling installations in commercial and institutional buildings have shown that temperature stability impacts people’s perception of comfort. If the temperature fluctuates significantly, occupants’ complaints increase significantly as well.  

With on/off actuators, there’s a greater difference in flow through the valves, which leads to greater room temperature deviations. This can lead to room occupants adjusting the room thermostat away from the set temperature, which causes even more temperature deviations, and leads to more complaints.  

Modulating actuators, on the other hand, keep the room temperature stable. Instead of the sudden temperature swings with on/off actuators, adjustments occur gradually, giving the heating source or chiller enough time to adjust to the right level. This even means you can increase cooling setpoints and decrease heating setpoints without impacting the perceived comfort level, because temperature control is stable. So, you lower the energy bill, increase the perceived comfort level and lower the pumping cost needed to achieve the desired room temperature setting – all in one go.  

This is not to say that on/off actuators don’t have their place within a building’s heating or cooling system. They work well for heating and cooling applications with a slower response, such as with floor heating. However, if a building’s heating or cooling is air-based, such as the fan coil units in our test scenario, the response time is shorter, and modulating actuators are better suited.  

Raising the efficiency bar with the new AME 110NL/X   

So, modulating actuators offer greater energy efficiency and more stable temperatures than their on/off counterparts. Job done? Not quite. Our development team has been looking for ways to make modulating actuators even better, and the results are the new AME 110NL/X actuator.  

The second-generation AME 110NL/X uses less power than its predecessor, which helps to lower the system’s overall energy costs. It features a digital step motor with a resolution of 1,000 steps per millimeter over the AB-QM 4.0 design flow valve stroke. This enhances the control performance of AB-QM valves, which also improves system efficiency and flow regulation. The AME’s improved IP54 rating provides robust protection against water ingress, so the actuator can be used in a wide range of environments and locations. And with its simplified setup process and user-friendly features, it’s never been easier to ace a building efficiency exam. Let us help you get to the top of the Energy Class.  

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