Choosing the best fan solu­tion for a partic­ular appli­ca­tion is crucial to the perfor­mance and effi­ciency of the system as a whole. If the fan selected is not powerful enough it will not provide the required volume of air. If it is over-dimen­sioned, the fan will use an unnec­es­sary amount of energy. The FanScout from ebm-papst helps plan­ners and users find just the right fan for the specific appli­ca­tion involved.

Figure 1: The FanScout selec­tion program from ebm-papst enables the most econom­ical fan combi­na­tion to be iden­ti­fied, including FanGrids.

Choosing the wrong fan for a computing center can prove to be a costly busi­ness, as cooling accounts for around 37 per cent of the energy costs in such cases. It is there­fore imper­a­tive to ensure that fans oper­ated in parallel, so-called FanGrids, are of optimum design (Fig. 1, page 6). The parallel oper­a­tion of multiple small fans has huge advan­tages over large indi­vidual fans in venti­lation tech­nology. The more uniform flow through the heat exchangers or filters leads to better heat transfer perfor­mance and more effi­cient filtering of the air (Fig. 2). In addi­tion, several small fans require much less space, which reduces the costs of the system.

Real measured values as a basis

Figure 2: Air flow through a heat exchanger with a FanGrid solu­tion (top) and an indi­vidual fan solu­tion (bottom). The latter exhibits non-uniform flow through the heat exchanger and thus poorer heat transfer values.

To avoid the nega­tive conse­quences of using inap­pro­priate prod­ucts, ebm-papst has created reli­able fan selec­tion soft­ware known as the ebm-papst FanScout. This provides air condi­tioning and venti­lation system plan­ners and manu­fac­turers with a quick and easy means of finding the ideal product for a partic­ular appli­ca­tion. The soft­ware takes up to five different oper­ating points into consid­er­a­tion and works with real measured values. The discrep­ancy between the calcu­lated oper­ating data and the actual measured data is so slight that the TÜV SÜD certi­fi­ca­tion body has confirmed the top accu­racy rating of the soft­ware. This means users receive absolutely reli­able and above all extremely precise data. The program does not simply measure the perfor­mance of the indi­vidual fan compo­nents, but rather assesses the fan system as a whole, made up of the fan impeller, EC drive motor and inte­grated control elec­tronics, based on the “Wire-to-Air” prin­ciple (from elec­trical hookup to the avail­able air perfor­mance).

High-preci­sion selec­tion proce­dure

The selec­tion process outlined below shows just how easy it is to design a FanGrid, for example, using the FanScout. Following initial consul­ta­tions, ebm-papst first narrows down the number of poten­tially suit­able fans and produces a so-called FanScout collec­tion. Users can already pick out fans at this stage with the help of the actual soft­ware. Up to five different oper­ating points can be entered. The oper­ating times at each of these oper­ating points viewed over the course of the year yield the usage profile which then serves as a basis for calcu­la­tion. This method provides a reli­able indi­ca­tion of the annual energy consump­tion and thus of the expected oper­ating costs. Such an approach is far more accu­rate than the commonly employed method of performing calcu­la­tion on the basis of the rarely attained maximum oper­ating point.

Redun­dancy provides oper­a­tional reli­a­bility

Figure 3: Three FanGrid oper­ating situ­a­tions: Normal oper­a­tion with all fans, redun­dant oper­a­tion (here n+1) with back­ward flow and redun­dant oper­a­tion (here n+1) without back­ward flow.

FanGrids for air handling systems are designed with some level of redun­dancy to guar­antee the required air can be deliv­ered to the building at all times.This para­meter spec­i­fies how many fans can be switched off without drop­ping below the required air flow. Two impor­tant aspects have to be consid­ered. Firstly, the reserve capacity of the remaining fans must be suffi­cient to make up the amount of air not being supplied by the non-func­tioning fans. Secondly, it must also be possible to provide compen­sa­tion for the amount of air flowing back through the stationary fans. A distinc­tion is made between the version with a back-flow flap, in other words with no back­ward flow, and the version without a back-flow flap. This is also presented in the FanScout (Fig. 3).

The space avail­able for instal­la­tion can also be spec­i­fied. This option is partic­u­larly useful in cases where the instal­la­tion space for the fans is extremely restricted, as the func­tion takes into account the pres­sure losses which arise if fans are fitted too close to walls or other fans. A further option then makes it possible to narrow down the fan type required and the total number of fans to be fitted.

Detailed infor­ma­tion on possible options

Figure 4: The results list provides an overview of various FanGrid combi­na­tions and their energy consump­tion.

The FanScout calcu­lates various possible FanGrid combi­na­tions on the basis of the para­me­ters entered and lists them according to their energy effi­ciency (Fig. 4, page 7). In addi­tion to energy consump­tion, the results table provides infor­ma­tion on the recom­mended fan type, the number of fans oper­ating in parallel and the speed factor. This factor indi­cates the differ­ence between the oper­ating speed of the selected fans and the nominal speed of the fans and is thus a measure of the “reserve capacity” of the chosen alter­na­tive.

Figure 5: The sound power of the indi­vidual fans can be shown for either the intake or the outlet side.

Air perfor­mance, power consump­tion and effi­ciency are presented in map form for each fan combi­na­tion. The spec­i­fied oper­ating points are also entered in the maps and the oper­ating time share of each is indi­cated by the size of the points. In addi­tion, the FanScout provides infor­ma­tion on noise for the possible fan combi­na­tions (Fig. 5). It shows the sound power of a fan – either on the intake or the outlet side – for each oper­ating point. This feature is partic­u­larly useful if a FanGrid is to be used in noise-sensi­tive envi­ron­ments such as offices or resi­den­tial areas.

Life­cycle costs in focus

To add further weight to the assess­ment of the various options for the user, the FanScout offers a func­tion for deter­mining the life­cycle costs of the combi­na­tion under consid­er­a­tion (Fig. 6).

Figure 6: Calcu­la­tion of the life­cycle costs provides a solid foun­da­tion for invest­ment deci­sions.

This involves multi­plying the power consump­tion of the fans at the respec­tive oper­ating points by the oper­ating time and the 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 the user with a real­istic cost assess­ment and forms a reli­able basis for invest­ment deci­sions.