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
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.
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.
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.
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.
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.
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