© ebm-papst

Making the perfect bath­room fan

Three years of joint devel­op­ment efforts by LUNOS and ebm-papst went into Silvento ec venti­la­tors – along with the under­standing that candor and trust are essen­tial to the successful comple­tion of such an exten­sive project.


If Rainer Müller were asked what his dream devel­op­ment project looks like, he would answer: “It would be great if we always knew from the begin­ning what we wanted at the end – and if nothing ever changed after that.” Müller says that with a laugh. As head of the Devel­op­ment Depart­ment for Product Section A1 at ebm-papst in Mulfingen, he knows that his wish will never come true, espe­cially when a new product is involved. The Silvento ec from LUNOS is an example. Rainer Müller’s project team devel­oped it in coop­er­a­tion with its Berlin-based manu­fac­turer. By using EC fans in these venti­la­tors, LUNOS took a pioneering role and needed to approach the market cautiously. The features the new venti­la­tors would need in order to stand out were clear. “High effi­ciency and low noise were the top prior­i­ties for us,” says Michael Merscher, tech­nical director at LUNOS.

Constant change

Michael Merscher, technical director at LUNOS

Michael Merscher, tech­nical director at LUNOS (Photo | Ange­lika Gross­mann)

The two compa­nies worked on the inline venti­la­tors for bath­room and restroom appli­ca­tions for three years, an unusu­ally long time for a devel­op­ment part­ner­ship.
The main chal­lenge was that there were two parallel devel­op­ment processes for the Silvento ec venti­la­tors. While ebm-papst worked on its fan, LUNOS tinkered with its end product. The effects every change had on the other compo­nents had to be taken into account.
“We didn’t have final control elec­tronics until shortly before the start of produc­tion, and our fan also changed during the devel­op­ment process,” says Müller. “Of course that’s a chal­lenge for both sides. The condi­tions can change suddenly because there are some things that can only be tested at a certain time.” So both sides had to be flex­ible – and willing to call the current status into ques­tion at any time.

Could be even quieter

Müller and his team (Image above: project leader Johannes Ehrhardt and Rainer Müller) adopted different approaches during the project’s three-year dura­tion. The orig­inal motor design fulfilled the effi­ciency and noise require­ments spec­i­fied at the begin­ning, but the project group still wasn’t really satis­fied with the way the venti­la­tors sounded. “So we dumped the initial design and started with another one,” recalls Müller.

Silvento ec – quiet and effi­cient:

  • The Silvento ec has a power consump­tion ranging from 1.8 to 13.8 watts. For the previous version, the range was 5 to 35 watts.
  • The lower power consump­tion means that the Silvento ec saves about 45 euros per year in contin­uous oper­a­tion at 60 m³/h.
  • Its noise level is up to 3 deci­bels lower, making it only about half as loud as its prede­cessor.

Until then, energy effi­ciency had played no role in bath­room and restroom venti­la­tion. But both compa­nies saw an oppor­tu­nity to score points with end customers, and they made use of it. AC fans had been used for these appli­ca­tions previ­ously. For the new venti­la­tors, ebm-papst devel­oped a new fan using EC tech­nology. “But for easy replace­ment, it had to be compat­ible with the prod­ucts that were already installed,” says Müller. The result is a logical refine­ment of the AC design, with the require­ment to reduce noise and increase effi­ciency.

Combined exper­tise

“When we started the project, we estab­lished that we would bundle our core exper­tise. A quiet and effi­cient fan from ebm-papst combined with appli­ca­tions exper­tise from LUNOS,” says Müller. “We did that using an inter­face that Michael Merscher and his team based on the regu­la­tion tech­nology they devel­oped.” LUNOS changed the pres­sure-air flow curve with a regu­la­tion algo­rithm to keep the air flow constant in every conceiv­able instal­la­tion scenario. “Without addi­tional sensors, the venti­la­tors can attain air flow constancy for wind loads up to more than 400 pascals,” says Merscher. “Both compa­nies contribute their expe­ri­ence here: ebm-papst provides optimum control for the venti­la­tors and LUNOS gives them the unique char­ac­ter­is­tics of its regu­la­tion tech­nology.”

Shared trust

What nobody knew when the devel­op­ment part­ner­ship started is now clear: The effort was worth it. The Silvento ec venti­la­tors have been well-received by the market and have even won prizes. They received the Plus X Award, an inno­va­tion prize for tech­nology, sports and lifestyle prod­ucts, as product of the year for 2016/2017. Looking back, Merscher and Müller agree that flex­i­bility and mutual trust are the basis for success in a devel­op­ment part­ner­ship. “After all, both sides reveal things with a lot of inno­v­a­tive content at an early stage,” says Müller. “You really need a partner you can trust,” agrees Merscher. And an ongoing, in-depth exchange of infor­ma­tion is indis­pens­able for reacting quickly to possible changes. “Who knows at the begin­ning of such a project exactly what he’s actu­ally going to need in two years?” says Müller with a wink. “We’re constantly refining the tech­nology.”

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