HOT | COOL NO. 2/2022 - "Conversion from gas - Diversity...

Transition towards low-temperature operations Key strengths & differentiators are that this concept is a world 1 st type of solution that allows for dry installation, provides con- tinuous valve commissioning, and solves both hydronic imbal- ances & return temperature optimization. However, there is a mass of opportunities with the solution: its unmatched versatility - as it can be used as a stand-alone solution without connecting it to the internet. In public build- ings, the solution can be bundled with accessories, such as tamper-proofing (protective cases) and main power supply modules. The concept endeavors to solve key pain points with hydronic imbalance removing costly installer calls and labor needed to fix claims that may arise. It provides preemptive maintenance, live access, and monitoring in a simple and eas- ily integrated, digitally fit solution.

costs. In boiler applications, the boiler’s efficiency will be in- creased, and the solution implementation will also have a larg- er positive effect on the hydronic balancing in buildings. The concept will address both buildings with known problems with return cooling and balancing issues, as well as typical buildings where cooling and energy efficiency can be at least optimized, if not radically improved. Testing the functionality The prototypes of the thermostat were installed on all radia- tors in part of two buildings to test the functionality of the new thermostat. Measurements on the heating system operation before, during, and after the test were collected and analysed to document how the thermostats performed to limit the re- turn temperature to the district heating substation and ensure hydraulic balancing in the heating systems. The new electronic thermostats were tested in two multi-fam- ily buildings in Denmark, both connected to the local DH net- work. The results documented that this prototype thermostat can embed the functionalities of the traditional thermostatic radiator valve and the riser balancing valves in the same de- sign. Integrating an extra return temperature sensor ensured better flow control through the radiators and the lowest pos- sible return temperature. In addition, installing these thermo- stats can allow the automatic hydronic control of the heating system, making the risers balancing valves redundant. It was found in Building A that the DH cooling – defined as the dif- ference between the supply and return temperature – was 4-12 °C higher in 2019 during the test compared to winter and spring 2020 when the prototypes were replaced with state-of- the-art thermostats. The measurements also suggested how the optimal oper- ation in large buildings is sensitive even though the build- ings have a well-controlled heating system. Only two un- controlled radiators out of 175 were able to contaminate the overall return temperature in Building B. In one case, the reason was a manufacturing problem – which was an acceptable issue in the development of a new product – whereas, in the second one, it was due to the end-user tam- pering with the thermostat. This last aspect can be poten- tially critical for any space heating system control. The results highlighted the importance of remotely connected devices. The measurements from the thermostats helped pinpoint the faults in the heating system, although the end-users were not experiencing any discomfort. By also correcting the pump setting and closing the string balancing valves in the two risers to limit the flow to the uncontrolled radiators, it was possible to reduce the overall return temperature to 35°C, neutralizing the negative effect of the malfunction- ing thermostats. Hence, the digitalization of the demand side represents a critical element for the transition towards low-temperature operations and can support and improve the quality of the activities of the building service person- nel, currently, labor and time-consuming because manually performed.

The concept is also ground setting for savings through sched- uling in large-scale public buildings.

These learnings will lead to further improvements of the sys- tem and give a lot of learnings of the effect in district utility grids and larger gas-boiler-fired installations. Furthermore, based on the massive amount of data gathered in the two test buildings, we can now see that the data can be used to diagnose various kinds of errors in how the heating systems are built and used. This could potentially lead to ad- vanced diagnostic systems that can monitor vast amounts of radiators and buildings. Having this in place could save a lot of time for janitors and en- gineers to supervise and troubleshoot installations, saving time and money in housing associations, municipalities, etc. The key finding for future product development is to secure the most robust design that could minimize the negative im- pact of the end-user’s misuse of local controllers in the heat- ing elements. An improved design may integrate a new safety functionality that closes the valve or limits the flow to a min- imum in case of damaged thermostats or wrong signal from the sensors. This will not be detrimental for the indoor com- fort in the flats and avoid a few radiators compromising the low-temperature operation of an entire building. The assessment of implementing low-temperature district heating grids shows that the existing grid can lower the tem- peratures. It might be legally possible for the district heating companies to support the transition to low temperatures by investing in intelligent thermostats. Furthermore, the results showed that the digitalization of the demand side represents a critical element for the transition towards low-temperature operations and the overall green transition.

For further information please contact: Ida Bach Sørensen,

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