RadiPac & FanGrid – Optimum Solution for AHU’s

By Helen McHugh - Head of New Product Research - 19th February 2018

HVAC equipment typically accounts for 40% of a commercial buildings electrical power consumption. This statement provides a compelling case for businesses to install the most energy efficient equipment in their buildings. Whether you are planning to install new equipment or upgrade existing equipment, one of the essential elements in delivering the best energy efficiency is to install EC fans. Fans account for as much as 60% of the power consumption of equipment such as AHU’s, therefore by selecting the most efficient fans and optimising the system design, significant savings can be achieved.

Traditionally AHU’s have used large belt driven AC blowers, however backward curved centrifugal fans or plug fans with EC motors are becoming increasingly popular. The EC plug fan not only gives the maximum energy efficiency, but is also a much more flexible solution which can adapt to varying conditions and easily connect to the Building Management System (BMS) as a result of the built-in speed control and electronics.

The ebm-papst RadiPac centrifugal fan is ideally suited for use in AHU’s for both new equipment and as a retrofit option. It has been designed to give optimum performance and efficiency, combining the Greentech EC motors with an aerodynamically optimised impeller. In addition, the RadiPac construction as either a cube or spider frame design makes it simple to mount in any orientation, and ideal for using in a FanGrid arrangement which gives added flexibility and enables a wide range in performances to be achieved.

  • RadiPac Sizes 250 to 1,000mm
  • Output power 500W to 12kW
  • Airflow 300 to 40,000 m³/h.

RadiPac Design

Using aerodynamic modeling, the impeller geometry has been optimised to reduce losses created through turbulence, which in turn leads to improvements in airflow, efficiency and noise.

Design changes include the inlet ring which is adapted to suit the new blade geometry, the motor position has been pushed back to allow air to be drawn into the fan more smoothly, whilst still maintaining a compact design.

The unique impeller geometry incorporates an airfoil blade with a hollow aluminium construction, this design reduces pressure losses at the inlet. The hollow construction reduces the overall weight of the impeller which increases efficiency and stability. The trailing edge of the blade combined with the integrated rotating diffuser results in reduced pressure losses at the outlet.

The result is a higher airflow, improved energy efficiency and noise reductions in excess of 3dB(A).

The design of HVAC applications can often be a compromise due to space restrictions, and as a result the fan can have insufficient space to operate at its optimum efficiency. This not only results in reduced performance but also increased noise. The RadiPac centrifugal fan is designed to discharge the air at an optimised angle to reduce turbulence and pressure drop in the application, thus enabling a higher performance to be achieved together with reduced power consumption and noise.

Performance - Peak efficiency

The RadiPac range provide airflows of up to 40,000m3/h and efficiency of well over 60%, and crucially this peak efficiency can be maintained across a wide performance range, which means the lowest possible power consumption at any operating point. This wide peak efficiency can result in significant increases in the overall system efficiency.

Easy commissioning: Plug & Play

The EC motors with their onboard electronics enable infinitely variable speed control and communication via 0-10V input or MODBUS RTU making commissioning simple, and accurate adjustment of fan speed to meet individual requirements.

Noise Reduction

In addition to the advances in impeller design, the FlowGrid inlet grille can be combined with the EC fans to further reduce noise.

In an ideal fan installtaion sufficient space would be left around the fan to allow a laminar airflow, however this is rarely possible as most installations have limited space which compromises the airflow resulting in turbulant air. On entering the fan the turbulant air hits the rotating blades generating a tonal noise or blade passing frequency.

Fitting FlowGrid to the inlet of the fan straightens the airflow resulting in a considerable reduction in sound pressure level of up to 3dB(A), and a drastic reduction in the low frequency tonal range of up to 12db.

FanGrid is a simple but effective addition used with RadiPac fans in FanGrid arrangements.

System Design - FanGrid

Whilst the performance and efficiency of the individual fans is optimised, this is no guarantee that the overall system efficiency will be maximised, to achieve this it is important to consider the installation.

The RadiPac is supplied with support brackets making installation simple. The bracket design can either be an X frame or a Cube construction, both have integrated inlet ring & the option to decouple the fan from the environment by the addition of suitable anti vibration fixings. The RadiPac construction enables numerous mounting options to suit a range of applications. One approach that can deliver maximum performance and flexibility is to adopt a modular approach and install in a FanGrid arrangement.

In a FanGrid, multiple fans are mounted together and operated in parallel, the result is a much higher performance and an improved use of the available space. This modular approach has unlimited scalability and gives increased operational reliability through redundancy. Coupling this with the EC RadiPac fan allows control and monitoring via MODBUS-RTU and/or 0-10 V/PWM; this gives a flexible, easily transported, efficient solution that has much better control of airflows and simple integration into BMS (Building Management Systems).

As FanGrids incorporate multiple fans, it is simple to build in redundancy, whereby if one fan fails, the speed of the others is automatically increased to provide the best possible compensation for the loss of air performance.

The RadiPac impeller design is well suited to the FanGrid installation, as its angled blades ensures the best possible airflow even when the space is restricted.

To assist with the design of the optimum FanGrid solution, ebm-papst have created Product Selector software FanScout. The most economical solution is worked out based on parameters such as the duty point range, installation space, and the desired level of redundancy, and can also take account of any installation losses.

Unlike traditionally fan selections which use the maximum operating point of a system to calculate the most efficient solution (even though the maximum operating point may only be required for a few days a year), the ebm-papst software uses the range of duty points that are required and the percentage time spent at each duty over a year, this calculation means the overall efficiency is optimised resulting in significant savings.

Case Study – Birmingham Ariport

This FanGrid design was used in a recent upgrade for Birmingham Airport.

A contra-rotating axial fan served the air conditioning system for the check-in area of Birmingham Airport. When the motor of the fan broke down, the entire air conditioning system shut down. Instead of replacing the big contra-rotating axial fan, ebm-papst UK replaced it with a new FanGrid design with five RadiPac EC fans.

The retrofit has reduced Birmingham Airport’s power consumption of 24 kW to 6.6 kW. Its energy consumption is reduced by 72 percent and saves the airport over €12,000 per year.

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