Heat recovery and distribution at optimum temperatures

There is still more to be gained

Fig. 2: Maria and Harald Landerl think the new heating concept in their SPAR market is simply brilliant.

“In our case, it was a defective circulation pump that tipped the scales,” recalls senior partner Harald Landerl. For 37 years, his wife Maria has been running the only grocery store in Reichraming, Upper Austria. They have been living there for just as long, as has their son Harald with his family. “Our well-known heating engineer Raimund Aschauer came by and took the opportunity to have a look at everything. His conclusion: Harald, there’s something to be gained from your system.” “Our trusted heating engineer Raimund Aschauer came by and took the opportunity to take a look at everything. His conclusion: Harald, there’s something to be gained from your system.”

At first, Harald Landerl was hesitant. After all, saving money always means investing money first. Ten years ago, this happened on a large scale.

The size of the market nearly doubled to its current area of 416 m². The 55 kW pellet boiler and a new 45 kW refrigeration system were installed. At that time, the size of the market nearly doubled to its current area of 416 m². The 55 kW pellet boiler and a new 45 kW refrigeration system were installed. Since then, a small portion of the condenser waste heat from the refrigeration system has been used to heat the small pool on the terrace from time to time. However, most of the heat energy was wasted in the environment, as is the case with many commercial refrigeration systems. There was indeed something to be gained here.

Aschauer came by and took the opportunity to take a look at everything. His conclusion: Harald, there is something to be gained from your system. the environment, as is the case with many commercial refrigeration systems. There was definitely something to be gained here.

Aschauer noticed another ‘weak point’. Since the conversion nine years ago, his son’s house, which is located higher up, has been connected to the heating system for the shop and his parents’ house via an approximately 20-metre-long pipe. This was a decoupled heating circuit, because due to the distance and, above all, the height difference of 22 metres, a heat exchanger had to be installed. Although this was a sensible idea, since then it had been necessary to switch manually between the two heating circuits. This was not very convenient and often meant unnecessarily high operating hours for the pellet heating system. A buffer storage tank was not available. Here, too, there was certainly room for optimisation. And then there was the heat distribution in the shop and the living areas via radiators and underfloor heating. There was no buffer storage tank. There is certainly room for optimisation here as well.

And then there was the heat distribution in the shop and living areas via radiators, underfloor heating and ceiling radiators. Since the entire hydraulic network is connected to only one heating system, the desired flow temperatures were achieved by adding cold water and distributing it with circulation pumps. This is still the case today in countless installations. Effective, but nevertheless a waste of energy.

50 per cent is possible

Fig. 3: Buffer tank with heat exchanger

Fig. 4: Heat supplier pellet boiler

With this knowledge, Raimund Aschauer then sat down with his partner Albert Koppenberger. After an initial rough assessment, they were able to give Harald Landerl some good news:

“If we couple the waste heat from the refrigeration system, install a buffer storage tank, convert the hydraulic system to Baunach rendeMIX mixers and equip the entire heating system with a modern control system, you can roughly halve your annual pellet consumption.”

refrigeration system

That was a promise! Since, according to initial calculations, the expected payback period for the conversion was around seven years, entrepreneur Landerl did not hesitate for long and placed the order. After all, the attributes ‘environmental protection’ and ‘resource conservation’ are very important to the trained toolmaker and helped him make his decision.

Two doers at work

Fig. 6: Holger Müller explains the functions of the rendeMIX in Wohnaus 1 (a second 2×4 mixer of the same design is now installed in the junior’s home).

Aschauer and Koppenberger (A & K) then developed a sophisticated system, hydraulic and control scheme. The subsequent discussion with Hauser was positive and resulted in the supplier of refrigeration units and refrigeration technology attaching a heat exchanger module to the new buffer storage tank customised by A & K . Since then, this module has been used to extract the condensation waste heat generated from the refrigeration circuit and feed it directly into the buffer at a temperature level of between 45 and 50 °C. As a supermarket refrigeration system has to be in operation all year round, there are hardly any phases without heat dissipation. If, however, the waste heat from the refrigeration system is not sufficient to generate the required storage temperatures, only then does the pellet boiler heat the double-layer buffer. However, if the waste heat from the refrigeration system is not sufficient to generate the required storage temperatures, only then does the pellet boiler heat the double-layer buffer storage tank with a capacity of 2200 litres. And if no waste heat is required, the installed axial condenser of the refrigeration system continues to be available for release into the outside air. the installed axial condenser of the refrigeration system is still available to release heat into the outside air.

The new hydraulic conductors

This measure alone was expected to result in significant savings. The second major potential then lay in heat distribution and heat buffering. Raimund Aschauer recalled a seminar held by HG Baunach GmbH. Holger Müller presented the rendeMIX in Wels at the time. A multi-path mixer that was just right. “When it comes to the efficient coupling of radiators and underfloor heating, our patented system delivers the best results,” said Müller. Fig. 7: Successful project partners (from left): Holger Müller, Harald Landerl Jr., Albert Koppenberger, Raimund Aschauer.

Fig. 7: Successful project partners (from left): Holger Müller, Harald Landerl Jr., Albert Koppenberger, Raimund Aschauer.

Another plus: the suction-operated circulation pump for the mixing circuit is already integrated into the assembly. Hydraulic switches, sensors or an additional control module are also unnecessary.

Conversion in just four weeks

Work began in August 2014. And within just four weeks, the job was done. The sheep’s wool insulated double-layer buffer storage tank was installed in the boiler room, which is located in an outbuilding between the two residential buildings (see diagram).

Fig. 8: Simplified diagram of the entire heating circuit, based on the actualconditions on site

The hot gas side of the combined system was connected to the heat exchanger module by the Hauser company. Then, an rMIX DN25 2x4 RH 35 was installed in the cellars of both residential buildings and connected to the heat supply on the flow and return sides, as well as to the radiator and underfloor heating circuits. At the same time, three circulation pumps became redundant. For the control system, electrical specialist Albert Koppenberger had devised a sophisticated concept. With the freely programmable UVR controllers from the manufacturer Technische Alternative, the system could be optimally adapted to the specific conditions on site. The system was then commissioned and tested. Electrical specialist Albert Koppenberger devised a sophisticated control concept. With the freely programmable UVR controllers from the manufacturer Technische Alternative, Amaliendorf, the entire heating system is now intelligently networked.

Fig. 9: New UVR controller in the boiler room

This has made manual intervention unnecessary. Instead, the heat energy is efficiently generated and buffered on the production side according to a logical function and only transferred to where it is needed. The flow temperatures for all heating circuits are now reduced to such an extent that there is no loss of comfort, but also only as much thermal energy as is required. This is ensured by the two rendeMIX mixers. The weather-compensated control system ensures that rooms do not cool down too much at night. The water in the heating circuits is therefore constantly circulated at a temperature between 38 and 40 °C. If one of the two boilers in the residential buildings requires higher temperatures between 6 a.m. and 10 p.m. , the flow temperature is temporarily increased to 55 °C and then lowered again once the storage tank has been filled. Only the boiler in the department store is electrically reheated to maintain the temperatures required by hygiene regulations.

Expected savings in sight

It was already clear at the time of the plant inspection at the end of February 2015 that Aschauer and Koppenberger had not promised too much. “Since the pellet boiler was installed nine years ago, I have always ordered fuel twice a year,” recalls Harald Landerl. “Thirteen tonnes in September and another ten tonnes in February. And now look how much is left after the first delivery since September 2014.” A glance into the storage facility reveals that it is still just under half full. “I won’t need to reorder until the end of the 2014/15 heating season. And there will probably even be some left over, meaning that we will effectively save between 10 and 12 tonnes of pellets.” This means that the reality is very close to the estimate of 50% that was made at the start of the project. Almost a perfect landing, in other words.

A positive conclusion

Fig. 10: The wonderful confirmation of a visionary idea. Albert Koppenberger with the certificate for the Energy Globe Award Upper Austria.

To sum up: the waste heat from a refrigeration system can be used to heat and provide hot water when there is a simultaneous demand for heat. Intelligent control is the key to demand-oriented heat supply. And the rendeMIX mixer prevents heat from being lost in heating circuits with different flow temperatures. The combination of these measures has saved the SPARmarkt Landerl around 50 per cent in energy and costs, and earned the two plant engineers, Aschauer and Koppenberger, the special distinction of the Energy Globe Award Upper Austria 2014 in the ‘Fire’ category. in energy and costs and earned the two plant engineers, Aschauer and Koppenberger, a special distinction: the 2014 Energy Globe Award for Upper Austria in the ‘Fire’ category. Once again, congratulations to everyone involved for a truly exemplary project – one that was made easy.

A positive conclusion

To sum up: the waste heat from a refrigeration system can be used for heating and hot water production when there is a simultaneous demand for heat. Intelligent control is the key to demand-oriented heat supply. And the rendeMix mixer prevents heat from being destroyed in heating circuits with different flow temperatures.

The combination of these measures has resulted in energy and cost savings of around 50 per cent for the SPARmarkt Landerl, as well as the Energy Globe Award Upper Austria 2014 in the ‘Fire’ category as a special distinction for the two plant engineers Aschauer and Koppenberger. Congratulations once again to everyone involved for a truly exemplary project – made simple. The combination of these measures has resulted in energy and cost savings of around 50 per cent for the SPARmarkt Landerl, as well as a special distinction for the two plant engineers, Aschauer and Koppenberger, in the form of the Energy Globe Award Upper Austria 2014 in the ‘Fire’ category. Congratulations once again to everyone involved for a real showcase project – made simple.

The rendeMIX can do more

In addition to coupling a high-temperature and a low-temperature circuit, as in the SPARmarkt Landerl example, the rendeMIX four-way mixer can also be used to couple a high-temperature and a low-temperature circuit with different flow temperatures.

The rendeMIX can do more

In addition to coupling a high-temperature and a low-temperature circuit, as in the SPARMarkt Landerl example, the rendeMIX four-way mixer can also be connected directly to a stratified buffer tank. It then enables two-zone charging and discharging. The advantage is that hot, cold and mixed water (through return flow utilisation) only flows in and out of their respective zones. This creates a safety shield in the middle of the buffer. The stratification in the storage tank is thus maintained. In addition to this effective loading, the rendeMIX also discharges a storage tank efficiently. This allows, for example, the operating time of solar systems or small CHP units to be extended economically. And because the return flow from the radiators becomes the flow to the underfloor heating, the water flows back to an oil or gas condensing boiler at a lower temperature. This produces more condensate and more condensation heat from the exhaust gas enters the heating water. This creates more condensate and more condensation heat from the exhaust gas enters the heating water. This effectively saves primary energy.

Achim Frommann

PR Werkstatt NutzWort

Sasbach (Germany)