© Ricardo Wiesinger | Fotogloria

Clever panels ensure lower costs

Systems specialist company hdt imple­mented a new venti­la­tion system solu­tion for the swim­ming pool at the Ring­hotel in Celle. The retrofit saves an enor­mous amount of energy.


A swim­ming pool and pigsty are more similar than you might think – at least when it comes to venti­la­tion require­ments. Although the air might smell consid­er­ably stronger in the sty, there is also a high humidity level there. At the Celle Ring­hotel, the task of removing this humid air was carried out by an old system equipped with AC fans until March 2019.

Retro­fitting to reduce costs

Love for the details: produc­tion manager Holger Bohlmann ensures the best quality with the final steps. (Photo: Ricardo Wiesinger | Fotogloria)

The system, which had become outdated, was resulting in oper­ating costs of around 12,250 euros per year. This encour­aged the hotel oper­a­tors to think about installing a more modern and energy-effi­cient system. The inquiry led them to hdt Anla­genbau GmbH in Diepholz. Word had got around about the exper­tise of company manager Hein­rich Dönsel­mann-Theile and his sons in all matters venti­la­tion.

“We carry out 20 projects each year and tailor every­thing to fit the design of the air duct on site,” says Christo­pher Dönsel­mann-Theile. “And what makes us special is that we make the hous­ings of our systems out of glass-fiber rein­forced plastic panels that resist corro­sion.” This is a major advan­tage when installed in a swim­ming pool, where the air is humid and contains chlo­rine, affecting metal compo­nents over time.

Instal­la­tion with obsta­cles

On an initial inspec­tion, the experts visited the site to get a first impres­sion of the system. It quickly became clear that access to the venti­la­tion system was very tight. There­fore, hdt quickly produced a 3D image of the aisles and the old system to deter­mine the best way to carry out the retrofit. The result: the deci­sion was made to supply the new system in two parts and to install them together on site. After a three-month plan­ning phase, the instal­la­tion began.

This came to fruition within two weeks. The old system was disman­tled and the new one was installed. It was not neces­sary to touch the eight venti­la­tion ducts on site. Instead, hdt designed the new system in such a way that neces­sary adjust­ments to the indi­vidual compo­nents of the system could be made in domestic produc­tion before instal­la­tion. It consists of a supply air filter, a supply air fan, a heating register, a heat exchanger module, and an exhaust fan. Both RadiCal fans are manu­fac­tured by ebm-papst and each offer a contin­u­ously adjustable power output of 0.14 to 0.79 kW.

Effi­ciency is every­thing

The new system is much more energy-effi­cient, and there­fore cheaper, than the old one. “Admit­tedly, it is slightly less effi­cient at heat recovery, but it is more effi­cient at venti­la­tion, which makes up for it,” says Christo­pher Dönsel­mann. The oper­ating costs following the retrofit speak volumes: they were cut to around 4,800 euros, i.e., by almost two thirds. To achieve this impres­sive result, hdt made use of the dryness of the outside air.

“With a swim­ming pool, it’s about dehu­mid­i­fying the air,” says Christo­pher. “If you can do this using an air condi­tioner that heats the air, you very quickly reach an output of 10 to 20 kW.” To do it more effi­ciently, a different approach is needed. “The outside air that we bring into the pool reduces the humidity inside. We simply venti­late and bring back the energy that we would lose, using heat recovery. Another benefit is that fresh air is always coming into the system,” explains Christo­pher. On a final note, he says that a key feature of this kind of system is that it does not require main­te­nance: “You take a look at it every two years and it’s still going.”

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