ECFanGrid

ECFanGrid

What is an ECFanGrid?

ECFanGrid is a multiple fan array designed to improve reliability, flexibility and efficiency in new or existing ventilation systems.

An ECFanGrid consists of several modular backward curved centrifugal fans or plug fans arranged in a grid construction offering numerous advantages over conventional technology. It is equally suitable for new projects and as a replacement for large single fans in retrofit air handling units.

In addition to being compact and flexible, the ECFanGrid is easy to clean, replace and maintain while expelling low noise and delivering uniform air stream. A uniform air stream improves the efficiency of other downstream components, for example, a thermal wheel. Learn more about the benefits of installing the ECFanGrid.

Axair will work with you to develop a specification that suits your project requirements. We supply the complete ECFanGrid kit which includes all mechanical parts: fans, wiring cabinet, grid construction and screws. We hold stock of all components to ensure short lead times and, on request, we will also supply the control cable, pressure hose, connectors and other ancillaries.

If you would like us to specify an ECFanGrid for your application, please complete our retrofit enquiry form with the necessary details and send it to sales@axair-fans.co.uk. One of our team of product sales engineers will be in contact.

Efficiency

Typically 40% of a commercial buildings energy use comes from heating, ventilating and cooling with 50% of the HVAC energy consumption coming from fans. The move from AC to EC fans in newer projects, has been significant due to their numerous advantages over their AC comparisons. EC fans can operate outside of their preferred operating range and still maintain a high efficiency, have reduced noise operation when speed controlled and the integrated motor and electronic makes for a compact design. Rosenberg EC fans also have built in controls and monitoring capabilities, enabling users to interrogate alarm outputs for fan faults, allowing individual problems to be addressed before total failure of the AHU. Savings as a result of moving from AC to EC occur from both improved motor efficiency and optimising system design.

EC plug fans

Redundancy

ECFanGrids provide superior reliability as a result of their inherent redundancy. If one fan fails, only that portion of the airflow is lost, unlike single fan systems where the entire air handler goes offline. Moreover, the loss of airflow from one plug fan can be offset by increasing the speed of the remaining fans; this can be achieved automatically in conjunction with the building’s BMS system. It allows for the facilities management team to plan for the downtime to suit the need of the building, for example, when the demands on the AHU are lowest. Read more about air flow in the case of a fan failure on the technical info tab.

Flexibility

The number of plug fans in each ECFanGrid system can vary according to the airflow requirements. For example, in a wall of 9 fans in a 3×3 configuration where only 7 fans may be required for normal operations to deliver the designed duty, the 8th and 9th space can be blanked off with a plate. If the demands on the AHU increase through building expansion for example, the blanking plates can be removed and 1 or 2 fans added to the grid to meet the new requirements.

Ease of Installation

ECFanGrids are ideally suited for retrofit AHU projects, particularly where a single large radial fan is being replaced. It is often the case that buildings have expanded around an AHU over its years of operation. This can make the extraction of the old fan problematic but the install of the new fan impossible without minor works to the fabric of the building. The ECFanGrid, due to its smaller component size, can be walked through standard pedestrian doorways by no more than two operatives: a significant factor in maintaining a tight replacement schedule and reducing costs when compared to alternatives. The use of plug fans, where time and space is an issue, risks the least downtime and offers the best opportunity for a rapid return to normal system operation.

ECFanGrid plug fans

Ease of Maintenance

Unlike a traditional belt drive unit which covers a large floor space, the ECFanGrid is completely free of the floor. This means that maintaining the hygiene of the AHU is quicker, simpler and more effective. No dust is released into the supply air as there are no belt drives to degenerate over time. Furthermore, component failure is quickly dealt with due to the modular nature of the ECFanGrid. For example, a single fan module could be replaced and the AHU back online within an hour of being shut down.

Noise Attenuation

Case studies show that sound is not an issue when using an ECFanGrid, on the contrary there will be more possibilities to significantly lower noise. When using an ECFanGrid there are two major advantages to attenuate noise. First, the noise spectrum of smaller impellers contains higher frequencies, thus the wave lengths are shorter, allowing for the use of shorter attenuators. Second, the required length of the fan section in a typical air handling unit, using a single large radial fan can be reduced dramatically – in some cases up to 50%. Read more about efficiency and noise within fan systems in our technical article.

Introduction

Axair’s team of product sales engineers are able to advise on best practice and provide technical support regarding the selection and installation of the ECFanGrid.  To provide an insight into ECFanGrid’s technology, information is listed below on:

  • Development of the ECFanGrid
  • How to determine spacing within an ECFanGrid
  • How to set up a constant air flow control
  • How to cover and handle a failure

To view the data sheets of the fans used within ECFanGrids, please see our backward curved centrifugal fans page and click on the product code.

Development of the ECFanGrid

Continuous and consistent airflow is essential to virtually every facility, making under-performing or unreliable fans simply unacceptable. In addition to reliability concerns, inefficient fans can be a building’s biggest energy consumer. Given the increasing cause for environmental concern, designers should look to select EC plug fans which will not only provide the necessary reliability, but also provide optimum efficiency and environmental benefits. In most fan systems a single fan is selected for the required system and various methods of control are also installed to meet other operating points defined by the system duty such as dampers or variable pitch blades. In some instances, it is advantageous to use more than one fan in a system, for example when it is necessary for the required operating range of the system to include multiple plug fans running closer to their peak efficiencies, instead of one large fan controlled over a wide operating range. Multiple fans for capacity control may be more economical if the cost of operation is critical. By running fans in parallel, when one motor fails, only a portion of the airflow is lost, unlike single fan air handlers.

Working with supply partner Rosenberg, we have developed an energy efficient solution to refurbishing old and outdated ventilation systems such as air handling units with an ECFanGrid.

How to determine spacing within an ECFanGrid

One of the more common questions regarding the design of the ECFanGrid relates to the recommended space between the fans to maintain optimum performance. To answer this, measurements were carried out in the Rosenberg certified testing labs on the impeller diameter and the duct dimensions to see how performance is affected by plug fan spacing. As a result, the following ratio was established:

A/D > 1.55

In the ECFanGrid selection process, if this ratio or a larger value is achieved, there will be no negative effect on performance. The calculation of the ratio consists of two basic steps:

1. To establish the A value, both the x and y dimensions of the duct are divided by the number of fans in each direction.

2. The result must be divided through the impeller diameter D of the fan

A good rule of thumb is:

Surround each fan with a quarter of its impeller diameter

How to set up a constant air flow control

Air flow with an ECFanGrid is measured by pressure taps in the inlet cone. Every inlet cone used with a Rosenberg EC Fan has a circular measurement tube with four measurement taps. The taps are arranged in order to obtain a correct mean value. This feature is critical if the air flow at the inlet is not even.

The pressure measurement is converted to actual air flow through the inlet cone. With the use of Bernoulli’s Incompressible Flow Equation and the Law of Continuity, the air flow is calculated by measuring differential pressure and applying a calibration factor. The actual measurement is the differential pressure between the inlet cone (measurement tube) and the inlet area of the application.

ECFanGrid fan wall plug

Air flow in the case of a failure

Shown in the graph below is an operating constant air flow control with a 3×3 ECFanGrid. As the curve indicates, the speed is changing and therefore the desired air flow is always maintained – 22.500 m3 /h (13,243 cfm). At the time t0, the damper was slightly closed and so the air flow in the system decreased. Hence, the ECFanGrid increases the speed to enlarge the air flow. The air flow reaches the desired 22.500 m3 /h (13,243 cfm) and the speed remains.

The ECFanGrid can be set up as a constant air flow system with a pressure controller used in 0-10 V open loop speed control as illustrated in the second image below. The desired set point is adjustable in the pressure controllers display menu.

Air flow in the case of a failure
ECFan Grid with pressure controller

How to cover and handle a failure

Redundancy is a major aspect as to why fans are connected in parallel.

Detecting a failure

Every fan used in a ECFanGrid has a potential free alarm contact. The contacts are COM, NO (normally open) and NC (normally closed). “Normally” means the fan is powered and no alarms occurred.

One approach is to connect and evaluate the alarm relay. It is possible to get one terminal for no failure and another terminal for failure. If two LEDs are connected to the respective terminals, the green one will light when all fans are running and the red one will light if one fan fails.

If a PLC is used to control the ECFanGrid, the fans can be connected. Again if one fan fails, the Digital 1 will appear at the input of the PLC.

In most cases, it is enough to know that there is a failure on the site. However, it is also useful to know exactly which fan has failed from a remote location. Therefore, using ModBus RTU to evaluate the alarms is recommended.

ECFanGrid Alarm Relay 1
ECFanGrid alarm relay 2

Closing off the open cone of the defective fan

There are three possible solutions. The first is to leave the cone open until the fan can be repaired. In this option, there are large losses and a high probability that the remaining fans will not succeed due to their performance limitations. If, despite of the losses, it is decided to leave the cone open, it may be an option to set the remaining fans to maximum speed to maintain an emergency mode.

However, if it is decided to close the open cone of the defective fan, there are two options:

  • Option A: Close off the open cone with a metal sheet
  • Option B: Provide auto-backdraft dampers for all fans

Backdraft dampers would only be of value in rare cases of a fan failure. The main benefit of using backdraft dampers is that the cone is closed automatically, however they will cause some losses. In units under lab test, a simple, sealed metal sheet was used to close open cones. In addition, the metal sheet should be reinforced due to possible static pressures of 1.000 Pa (4 inches) or higher while an average sized metal sheet of 0,25 m2 (2.69 f t2 ) – the actual force acting on the sheet is 250 Newton or about 25 kg (55 lb).

With pressure or speed control, closing the inlet cone is all that is required. With the use of speed control, the superordinate system must increase the speed. Whereas in case of a pressure control, the failure will be recovered automatically, within the fan’s performance limitations.

Action to take if the master fan fails

The solution is to change the master fan by using the measurement tubes from a different fan. This can be achieved by changing the wiring of the measurement tube. Therefore it is recommended to make all circular measurement tubes accessible from the outside. The air tube must be plugged from the master fan’s measurement tube to another fan’s tube.

Following a fan failure the ECFanGrid can be back in operation within approximately 15 minutes.

For example, take a 2×2 ECFanGrid with constant air flow control 25.000 m3 /h (14,715 cfm) with a selection of covering one fan failure. The key for the selection is to check if three fans are able to maintain the operating point. When a failure occurs, it is detected by evaluating the alarm relay of the EC Fans, as discussed previously. At this point, the Building Management System is displaying an alarm and the duty officer goes on site to check which of the four fans has a malfunction. They proceed to close the cone by screwing on the reinforced, sealed metal sheet. If it is a master fan failure, they would additionally change the measurement tubes. The duty officer must also increase the set point to maintain the designed operating point. The black vertical line in the diagram below is the required air flow per fan. The demanded total operating point is 25.000 m3 /h (14,715 cfm), which in turn is 6.250 m3 /h (3,679 cfm) per fan. The intersection between this line and the blue curve is the regular set point, which should be adjusted in case of no failure. In this example, one fan failure would mean the number of fans is reduced to three. Now, the set point of the intersection between the black vertical line and the red curve (representing 3 fans) should be set. Finally, the duty officer changes the set point from 600 Pa (2.4 Inches) to 1.050 Pa (4.2 Inches).

ECFanGrid air volume failure

ECFanGrid Case Studies

The ECFanGrid can be used in numerous applications due to its adaptability. Below are three examples of retrofitted ECFanGrids that replaced large single fans in air handling units (AHUs). The different sizes and configurations highlight the flexibility of the ECFanGrid.

Supply air for airport entrance hall

Specification
Input Power
CO2 Reduction
Payback Period
3×3 ECFanGrid with centralised controlling through a standardised wiring cabinet with integrated air flow measurement ECFanGrid 27kW 41A Forward Curved Impeller 35kW 67A 20 tonnes per year 2 years, 3 months

ECFanGrid airport supply air fan applications

Banknote printing

Specification
Input Power
CO2 Reduction
Payback Period
Two 3×3 ECFanGrids, one supply, one exhaust with centralised controlling through a standardised wiring cabinet 2 x ECFanGrids 46kW 70A 2 x Forward Curved Impellers 67kW 105A 100 tonnes per year 1 year, 6 months

ECFanGrid banknote printing fan applications

Supply air for drying wood

Specification
Input Power
CO2 Reduction
Payback Period
3×4 ECFanGrid with centralised controlling through a standardised wiring cabinet with integrated air flow measurement ECFanGrid 23kW 34A Axial fan 27kW 40A 12 tonnes per year 3 years, 4 months

ECFanGrid air drying wood fan applications

Axair supply the complete ECFanGrid kit which includes all mechanical parts: fans, wiring cabinet, grid construction and screws. We hold stock of all components to ensure short lead times and, on request, we will also supply the control cable, pressure hose, connectors and other ancillaries.

If you would like us to specify an ECFanGrid for your application, please complete our retrofit enquiry form with the necessary details and send it to sales@axair-fans.co.uk. One of our team of product sales engineers will be in contact.

How to Build

Part of the Axair team demonstrate the assembly of the ECFanGrid in the video below. This example uses three plug fans in a 2×2 grid. If you would like us to specify an ECFanGrid for your application, please complete our retrofit enquiry form with the necessary details and send it to sales@axair-fans.co.uk. One of our team of product sales engineers will be in contact.

Products in this range

ECFanGrid / Fan Wall

ECFanGrid is a multiple fan array designed to improve reliability, flexibility and efficiency in new or existing ventilation systems

B Wheel Motorised Impeller

Designed to increase energy efficiency by up to 6% and reduce noise by 3 decibels

E Wheel Motorised Impeller

The latest design which significantly increases energy efficiency and reduces operating noise levels

Meet our product specialists

Geoff Edwards

Business Development Director

Geoff has a background in engineering and many year’s experience in air movement. The next generation in the family business, he is passionate about delivering the best solution to our customers. His main focus is to drive down customer energy costs, improve system efficiencies and provide products that are easy to install and maintain.

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