Many appli­ca­tions require high air perfor­mance. Data centers, large indus­trial building complexes, hotels, resi­den­tial complexes and hospi­tals are all typical exam­ples. Replacing one large fan in central air condi­tioning systems with FanGrids containing several smaller fans that func­tion in parallel provides many bene­fits in prac­tice.

Smaller, more light­weight and simply better

Figure 1: To achieve high air perfor­mance in venti­lation tech­nology, large, single fans are no longer today’s preferred solu­tion. Instead, we recom­mend FanGrids: combining several smaller fans that work together in parallel. (Photo: ebm-papst)

In this way, the indi­vidual fans can be stacked or arranged in rows to use the avail­able space to maximum advan­tage (Fig. 1). Small fans require less instal­la­tion space and are easier to handle than one large fan. Thanks to the latter benefit, trans­port and instal­la­tion are less compli­cated and when a fan needs to be serviced, the system can keep running. The speed of the other fans is adjusted to main­tain constant air perfor­mance. During the selec­tion process, the rele­vant redun­dancy require­ments can be taken into account.

And the air distri­b­u­tion is much better when several fans are used. Upstream or down­stream compo­nents such as filters and heat exchangers receive a more even airflow (Fig. 2). This results in more effi­cient air filtering and improved heat transfer perfor­mance.

Today, the bene­fits of a FanGrid can be lever­aged in a wide range of appli­ca­tions. Motor and fan specialist ebm-papst supplies FanGrid modules with RadiPac or RadiCal centrifugal fans. Several fans func­tioning in parallel ensure the required volume of air. Axial fans can also be used in FanGrids: today, more and more data center oper­a­tors rely on “free cooling” (Fig. 3). In clas­sical AHUs, we recom­mend centrifugal fans instead because they are designed to work with higher back pres­sure. Various sizes with diam­e­ters between 400 and 560 mm are avail­able.

Figure 2: The air distri­b­u­tion in the FanGrid (right) is much better, upstream or down­stream compo­nents such as filters or heat exchangers receive a more even airflow than if a single fan is used. This results in more effi­cient air filtering and improved heat transfer perfor­mance. (Photo: ebm-papst)

Energy-effi­cient EC tech­nology with conve­nient closed-loop control

The driving force behind FanGrids are modern Green­Tech EC drives that func­tion highly energy effi­ciently in full and partial-load oper­a­tion, are designed for long service lives, and feature infi­nitely vari­able speed control. With over 90% effi­ciency, the motors deliver much more than the values required in effi­ciency class IE4. The flow machine design also contributes to increased effi­ciency and quiet oper­a­tion.

The FanGrid line is rounded out by a new controller from ebm-papst that easily acti­vates fans oper­ated in parallel. It requires minimal wiring work: all fans are simply connected via a RS485-MODBUS cable (passthrough). Autoad­dressing makes commis­sioning easier and indi­vidual addresses can be adjusted directly. The controller has even more to offer. It has a 0-10 V inter­face for posi­tioning commands for synchro­niza­tion from 0 to 100 percent, for example.

A pres­sure sensor on one of the fans enables volume flow control to opti­mally adjust air perfor­mance to changing circum­stances such as clogged filters. Temper­a­tures and speeds can be read out for indi­vidual fans or specific groups. The rele­vant status and failure messages can be trans­mitted directly to the moni­toring system. Users always have an eye on the FanGrid fans and if neces­sary, can plan preven­tive main­te­nance on their AHUs.

Figure 3: “Free cooling” is becoming an increas­ingly popular alter­na­tive for data centers. Multiple Green­Tech EC centrifugal fans from the RadiPac or RadiCal product range operate in parallel to supply the neces­sary volume of air. FanGrids with axial fans may also be used. (Photo: ebm-papst)

Cubes prevent instal­la­tion loss

Each centrifugal fan comes with tried and tested support brackets and can be installed in a cube made of molded aluminum parts and a support plate on the intake side. During the design phase of the cube-shaped housing, a key factor was taken into consid­er­a­tion that is often neglected in prac­tice: instal­la­tion loss. If fans are installed too close together, they will influ­ence one another. The rule of thumb: The greater the volume of air to be moved, the further apart the fans should be. To avoid instal­la­tion loss, the FanGrid module’s cube has extra generous dimen­sions.

The cubes can be stacked or arranged in rows in the device or pres­sure chamber. The FanGrid also reli­ably sepa­rates the intake and pres­sure sides from each other and customers only have to close the gaps on the wall or housing with bulk­head plates. FanGrid modules come as plug & play units with the asso­ci­ated mounting brackets or as complete kits for direct, on-site instal­la­tion. The kits consist of the fans, an air inlet grill, bulk­head plate, corner connec­tors, spacer profiles and bolts.

Figure 4: Flex­ible FanScout selec­tion soft­ware makes it easy to find the ideal fan combi­na­tion. (Photo: ebm-papst)

Fan selec­tion made easy

ebm-papst has a flex­ible selec­tion tool to help customers find their optimal combi­na­tion of fans: the ebm-papst FanScout (Fig. 4). Based on up to five appli­ca­tion-specific oper­ating points and the antic­i­pated oper­ating times, this selec­tion soft­ware deter­mines the most effi­cient FanGrid solu­tion. The amount of instal­la­tion space avail­able, maximum number of fans required, and redun­dancy require­ments can also be taken into account.

For the redun­dancy eval­u­a­tion, the soft­ware spec­i­fies how many fans can be switched off without drop­ping below the required air flow. Two impor­tant aspects have to be consid­ered. First, the reserve capacity of the remaining fans must be suffi­cient to make up for the amount of air not being supplied by the non-func­tioning fans. Second, it must also be possible to compen­sate for the amount of air flowing back through the stationary fans. There are two vari­ants: without back­flow and with back­flow. FanScout also maps this.

To add further weight to the eval­u­a­tion of the various options for the user, FanScout has a func­tion for deter­mining the life cycle costs of the combi­na­tion under consid­er­a­tion. This involves multi­plying the power consump­tion of the fans at each oper­ating point by the oper­ating time and elec­tricity costs, and adding up the total. The result repre­sents the pure oper­ating costs of the instal­la­tion over a spec­i­fied period. If the costs for purchase, instal­la­tion and service are also entered, the overall costs of the FanGrid over time will be displayed. This provides users with a real­istic cost assess­ment and a reli­able basis for their invest­ment deci­sions. 

Auto­matic reso­nance detec­tion for more oper­ating reli­a­bility

Centrifugal fans are used in a wide range of air condi­tioning systems. Depending on the instal­la­tion situ­a­tion, there may be reso­nance in previ­ously unfore­seen speed ranges. If the fan is often oper­ated in such crit­ical ranges, the drive motors’ bearing system may be damaged, leading to fan failure. For system oper­a­tors, these vibra­tions can be measured but are not easy to suppress. In its RadiPac centrifugal fans, ebm-papst solves the problem with an auto­matic reso­nance detec­tion func­tion that mini­mizes the effect of vibra­tions.

Figure 5: If exces­sive vibra­tion veloc­i­ties are detected in specific ranges (above), the control soft­ware auto­mat­i­cally sets itself to fast-forward through these speed ranges in the future (see fig. below). (Photos: ebm-papst)

A test start-up is carried out during commis­sioning in which the vibra­tion levels over the entire speed curve are analyzed. If exces­sive vibra­tion veloc­i­ties are detected in specific ranges, the control soft­ware auto­mat­i­cally sets itself to fast-forward through these speed ranges in the future (see Fig. 5). In this way EC centrifugal fans can be oper­ated without risk of damage. Oper­a­tors can manu­ally edit the soft­ware settings at any time and always have full control.