The cafe­teria at the Diakonie-Klinikum Stuttgart is a place for everyone: patients can dine with their loved ones, visi­tors can grab a coffee and staff can take a short break from their daily hospital routine. In the kitchen behind the cafe­teria, fresh meals are prepared daily—for many people and a wide range of needs. For the cooks, this daily routine can some­times be stressful, espe­cially when the venti­lation system fails—which is exactly what happened in the spring of 2026.

Cooking gener­ates heat, mois­ture, odors and greasy exhaust air. All of this must be safely vented while simul­ta­ne­ously allowing an inflow of fresh air. So when the roughly 25-year-old belt-driven fans in one of the kitchen’s four venti­lation systems were no longer able to cope with the load, the system failed. The situ­a­tion rapidly became critical—for working condi­tions, hygiene and food service. 

“It was impor­tant to us that the kitchen staff could quickly return to working under safe and reli­able condi­tions,” says Klaus Uetrecht, tech­nical director of the Diakonie-Klinikum Stuttgart. Accord­ingly, ProAc­tiveAir, a long-standing partner of the hospital, under­took a retrofit of the kitchen venti­lation system, and turned to ebm-papst for the design of the new fan tech­nology. Together, they iden­ti­fied four systems for modern­iza­tion: one large supply-air system and three exhaust-air systems for the various kitchen areas.

This also aligned with a broader goal of the hospital. The Diakonie-Klinikum Stuttgart’s Green Team spans various profes­sional groups—from medi­cine and nursing to engi­neering and human resources—and is committed to the hospital’s sustain­ability goals. In the tech­nical depart­ment, the primary focus is on reducing energy consump­tion and CO₂ emis­sions. Outdated venti­lation systems are a key area for improve­ment here: They often don’t operate according to actual needs, and thus they consume energy unnec­es­sarily.

Retrofit without disrupting hospital oper­a­tions

Despite the venti­lation system being out of service, staff, patients and visi­tors natu­rally couldn’t go without meals. Kitchen oper­a­tions there­fore continued as usual—and the retrofit had to take place during breaks in food prepa­ra­tion. For the teams from the building services, ProAc­tiveAir and ebm-papst, this meant an unusual work schedule—the systems that were still oper­a­tional would be shut down starting in the after­noon and had to be running reli­ably again by around 6 a.m. each morning.

The tech­ni­cians removed the old fans, installed the new equip­ment, inte­grated it into the existing building manage­ment system, and brought the systems back online—all overnight. The exhaust air from the hot kitchen posed a partic­ular chal­lenge: The grease-laden air gener­ated there must be safely and sepa­rately vented for fire safety reasons. For this reason, each of the four systems required its own tech­nical solu­tion.

In the large supply-air system, a FanGrid consisting of four RadiPac C fans oper­ating in parallel has replaced the previous single fan. If one of the modules fails, the others continue to run, ensuring unin­ter­rupted operation—a crucial advan­tage in a kitchen envi­ron­ment. The smaller exhaust-air system was modern­ized with a single RadiPac C. In the two large exhaust systems for greasy kitchen exhaust air, a total of six special radial fans with exter­nally cooled elec­tronics are now in oper­a­tion. The advan­tage: The motor elec­tronics are cooled sepa­rately so that they operate reli­ably and do not overheat—even with warm, greasy exhaust air. 

On consec­u­tive nights the team upgraded the kitchen venti­lation system in the existing building—without inter­rupting hospital oper­a­tions. A total of eleven new fans are now in oper­a­tion.

Digital retrofit with NEXAIRA

But the retrofit was not complete with only the fan replace­ment. In addi­tion to the imple­men­ta­tion of the energy-effi­cient retrofit, ebm-papst recom­mended an addi­tional digital connec­tion for the new fans. For Klaus Uetrecht, this was a logical next step. “Digital moni­toring gives us the ability to detect issues in the system earlier,” he says. “This allows us to schedule main­te­nance more effec­tively and not wait for a malfunc­tion to react—as was the case with the old system.”

(Video | Lukas Zwies­sele)

NEXAIRA analyzes the data and presents it clearly via a dashboard—including oper­ating status, runtime, other rele­vant fan data and any alarms.

“A retrofit demon­strates its greatest value when it notice­ably simpli­fies the operator’s day-to-day work—through lower energy consump­tion, greater oper­a­tional trans­parency and a reli­able tech­nical infra­struc­ture. With NEXAIRA, we not only make existing venti­lation systems more effi­cient, we also make them smarter. This creates tangible benefits—economically, ecolog­i­cally and in day-to-day operations—especially in sensi­tive build­ings like hospi­tals”, says Dr. Klaus Geißdörfer, CEO of the ebm-papst Group.

One sensor in each system also measures the differ­en­tial pres­sure across the filter. This allows NEXAIRA to detect when a filter becomes clogged and the fans need to increase their output. In addi­tion to detecting filter clog­ging, NEXAIRA offers other digital services: “Fan Health Status” assesses the condi­tion of the fans and provides an esti­mate of their expected service life, and moni­toring, alerts and heat maps show how the system is performing and where devi­a­tions occur. This allows the system to detect malfunc­tions earlier, supports targeted main­te­nance and ensures the systems operate effi­ciently.

Less energy, more visi­bility

The retrofit is paying off. The new fans consume about 40 percent less energy than the old equip­ment. In addi­tion, digital moni­toring provides greater trans­parency into ongoing oper­a­tions. The tech­nical team can now assess system condi­tions more easily and iden­tify poten­tial opti­miza­tions more rapidly.

The payback period is also only around two years. For Klaus Uetrecht, it is precisely this combi­na­tion that is crucial. “For us, oper­a­tional reli­a­bility is clearly the top priority,” he says. “Of course, the fact that the modern­iza­tion pays for itself through energy savings makes the project all the more worth­while.”

For the Green Team and the tech­nical depart­ment, the kitchen venti­lation system is an impor­tant first step toward more effi­cient building services. This is why the retrofit in the hospital kitchen won’t be their last project. Klaus Uetrecht and his team are already eval­u­ating other systems and deter­mining the optimal sequence for modern­iza­tion. In this way, this rapid solu­tion for the hospital kitchen is becoming a model for other systems in the building.