Today, impor­tant measures to save energy include building highly insu­lated low-energy houses and reno­vating existing build­ings by using insu­lating windows and thermal insu­la­tion composite systems on the building enve­lope. Sealing it off in this way means that only a small amount of heat energy is lost. However, this often results in no guar­antee of suffi­cient air circu­la­tion, as the manual venti­lation is usually less than is required. This may result in mold forma­tion, the repro­duc­tion of pathogens and a lack of oxygen.

Central­ized or decen­tral­ized?

Depending on how the building is used, plan­ners and oper­a­tors can choose between central­ized, decen­tral­ized or combined solu­tions. In the past, central­ized venti­lation has shaped the market.

In the mean­time, decen­tral­ized solu­tions for indi­vidual rooms or smaller units of use are also widely used, as they offer options for adapting to the user’s indi­vidual wishes, enable detailed indi­vidual billing and can usually be easily retro­fitted. In addi­tion, these devices are inte­grated directly into the building façade or windowsill and they do not require a duct system for supply and exhaust air. That is why they are ideal for reno­vating old build­ings.

In central­ized systems, heat recovery and air filtra­tion are easier and more effec­tive to imple­ment and performing main­te­nance work is easier to execute according to plan. Both solu­tions there­fore have advan­tages and can be combined if neces­sary.

Of course, the devices designed for the various venti­lation concepts require different fans. Motor and fan manu­fac­turer ebm-papst offers the right fan solu­tion for the various require­ments. The centrifugal fans in the RadiCal series are among those suit­able for the AHUs used in central­ized venti­lation concepts.

RadiCal in scroll housing for central­ized solu­tions

ebm-papst has taken a deci­sive step forward with the RadiCal in scroll housing. For the back­ward-curved EC fan, the company devel­oped a vane anemometer for the most precise air flow deter­mi­na­tion – with just a one percent toler­ance in the final value – and a closed scroll housing with inte­grated control elec­tronics. In addi­tion, the centrifugal fans are designed as a plug & play system, enabling venti­lation system manu­fac­turers to install them easily. Sensors for humidity and temper­a­ture are already inte­grated in the RadiCal. Other sensors, including those from third-party manu­fac­turers, can also be connected and the entire system can be read, moni­tored and controlled via an open MODBUS RTU inter­face.

Avail­able in five sizes between 133 and 225 mm, the RadiCal can be used in different build­ings and, in the largest version, achieves an air flow of up to 1,800 m³/h. The EC fans also achieve a 34 percent higher effi­ciency than compa­rable centrifugal blowers and are up to 3.5 dB(A) quieter than these. This means that the blade passing noise is also signif­i­cantly reduced. The compact construc­tion and new design enable different mounting vari­ants depending on the design of the venti­lation system.

Compact centrifugal fans for high air flow rates

Ever-lower energy consump­tion is required for devices in central­ized resi­den­tial venti­lation and air condi­tioning. Manu­fac­turers are responding to this by designing their devices for minimal pres­sure losses resulting from instal­la­tion. At the same time, venti­lation and air-condi­tioning devices need to be as compact as possible so as to mini­mize their foot­print and have suffi­cient space inside for addi­tional compo­nents. For this reason, there is a demand for compact fans that deliver large air flows with low back pres­sure while oper­ating as energy-effi­ciently and quietly as possible. ebm-papst designed the centrifugal fans in the RadiCal 2 series to meet precisely these require­ments.

Several design details contribute to this, making it possible to achieve a ‘wound’ blade geom­etry that helps signif­i­cantly increase effi­ciency and reduce noise. The blades are tilted both forwards and back­wards and the profile of the inlet and outlet edges has been revised. This improves the flow behavior while at the same time increasing the strength of the fan impeller, which is made of resis­tant plastic. The wavy cover plate also improves the aero­dy­namic char­ac­ter­is­tics and, as a result, the air perfor­mance.

With the centrifugal module, i.e. the housing box, the inclined struts further increase the air perfor­mance. The axial height of the struts is selected to fill the back­flow areas in the best possible way. There is also an enlarged intake diam­eter, which ensures a greater air flow rate through the impeller. The new, improved Flow­Grid reduces the fan’s noise gener­a­tion even with undis­turbed inflow and thus repre­sents a logical further devel­op­ment of the existing air inlet grille.

Room for room: decen­tral­ized venti­lation

Decen­tral­ized resi­den­tial venti­lation units installed in the façade are not only suit­able for reno­va­tion measures, but are also gaining in impor­tance in new build­ings where rooms have to be indi­vid­u­ally controlled, as in some resi­den­tial build­ings, in hotels and schools. Push-pull venti­lation units convey used air from the living space to the outside (push) for a defined period of time, usually around 60 seconds. The fan installed in the venti­lation unit then changes its direc­tion of rota­tion, i.e. it reverses (pull).

During push oper­a­tion, an inte­grated heat accu­mu­lator stores the heat energy from the exhaust air. In the pull phase, it is trans­ferred to the fresh outside air so that it flows into the building preheated. A filter also clears dust and pollen from the air coming in from outside. Two units per room or zone are required to ensure balanced venti­lation. In some cases, several rooms are venti­lated using one pair of units. Due to their posi­tion in the resi­den­tial and commer­cial rooms, decen­tral­ized units have to be partic­u­larly space-saving and quiet.

Push-Pull-Profi: AxiRev

In decen­tral­ized venti­lation units, the direct prox­imity of the fans to the outside air poses a partic­ular chal­lenge: they have to deliver constant, level air flows even in changing wind forces. The AxiRev 126 reverse fan from ebm-papst was specially devel­oped for this purpose. The char­ac­ter­istic curve for the pressure/air flow is very steep, which means that, even in stormy weather condi­tions, there are only slight fluc­tu­a­tions in the air flow. This means that wind and storms have little influ­ence on the effi­ciency and func­tion of the decen­tral­ized resi­den­tial venti­lation unit. In addi­tion, the conveyed air volumes are almost iden­tical in both direc­tions of rota­tion.

This is ensured by the “flat” symmet­rical blades that enable higher pres­sures and generate a very steep char­ac­ter­istic curve. Adjusting the number of blades and struts with an aero­dy­namic profile reduces turbu­lent trails. Together with the newly devel­oped, extremely low-noise EC motor, this creates an oper­ating noise that is perceived as pleasant.

The improved design also opti­mizes the effi­ciency: with a typical flow quan­tity of 42 m³/h per unit, the compact fan consumes less than two watts in a stan­dard device and remains partic­u­larly quiet, even in partial load and minimum oper­a­tion with high effi­ciency, thanks to the EC motor. The large speed range from 500 rpm to 4,200 rpm (vari­ants also up to 4,700 rpm) ensures optimum adap­ta­tion of the air perfor­mance to the require­ments. The compact design based on the prede­cessor model enables users to use the AxiRev 126 as a retrofit in a plug & play complete system. Compared to its prede­cessor, the new AxiRev 126 is more powerful, more pres­sure-resis­tant and quieter.

ebm-papst in venti­lation tech­nology