Understanding SFP in Air Handling Units

The air handling HVAC market is highly competitive, with a large number of AHU manufacturers working hard to improve the energy efficiency of client’s systems, improve sustainability, reduce carbon emissions and gain a competitive edge in the market. Therefore, the better their systems, the better their offer.

Specific Fan Power (SFP) is a parameter that measures and quantifies the energy-efficiency of fan air movement systems such as air handling units. It is typically expressed in terms of power consumption per unit of airflow, or expressed a different way, it is a measure of the electric power that is needed to drive a fan (or collection of fans), relative to the amount of air that is circulated through the fans. It is not constant for a given fan, but changes with both air flow rate and fan pressure rise. The SFP principle in fan selection is to choose a fan to deliver one flow at one pressure in a particular system using as less electrical energy as possible and all other factors being equal.

To calculate the specific fan power of a fan unit, you need to know the power consumed by the fan which can be found in your fan manufacturers documentation, along with the volume flow rate of air being moved.

SFP = (Fan Power Consumption) / (Air Flow Rate)  

The air flow rate can be determined from the design data, by taking airflow measurements or through calculations using the well documented fan laws formulas. For airflow measurement, situate a measurement device such as an anemometer or a flow sensor at a suitable location within the AHU ductwork and measure the airflow rate directly. Using fan speed information, you can use the fan laws to estimate the airflow rate. The fan laws state that the airflow rate is directly proportional to the fan speed. Specific fan power is an important metric for air handling unit manufacturers providing a measure of the energy efficiency of their equipment, that in a highly competitive market, can differentiate HVAC systems using comparable data.

A key factor is the fan-motor combination used in air handling systems. Energy efficient EC plug fans are invaluable in helping to provide the best efficiency, so the SFP figure is the measure often used for comparison. More often than not, utilising a low slippage high efficiency EC motor and drive combination is the key to achieving the highest efficiency. Many countries have implemented energy efficiency regulations and standards to promote the use of energy-efficient equipment. AHU manufacturers ensure that their products comply with these regulations. SFP is often used as a benchmark to determine the energy efficiency of AHUs.

Lower SFP values indicate higher energy efficiency, which can help manufacturers meet regulatory requirements and gain a competitive advantage in those markets. A lower SFP contributes towards operational cost savings. AHUs are typically operated continuously or for long periods, consuming significant amounts of energy. By designing AHUs with lower SFP values, manufacturers can help their customers reduce energy consumption and operating costs. Energy-efficient AHUs with lower SFP values require less power to move the required airflow, resulting in energy savings over the operational lifespan of the unit.   Energy consumption in buildings, including HVAC systems like AHUs, contributes to greenhouse gas emissions and environmental impact. AHU manufacturers are increasingly focused on developing sustainable and eco-friendly solutions. Lower SFP values translate to reduced energy consumption, resulting in a smaller carbon footprint and lower environmental impact. We have discussed sustainable air handling units and multiple fan arrays previously. Learn more about BREEAM assessments and how we can assist with removing old belt driven fan systems and replacing with EC plug fans, reduce scope 2 emissions and improve energy efficiency on short payback periods.

Building owners and operators are increasingly aware of the importance of energy efficiency and sustainability in their facilities. They often prioritise equipment with better energy performance to meet their sustainability goals and reduce operational costs. AHU manufacturers that can offer energy-efficient products with low SFP values are more likely to attract customers and secure contracts. The use of the SFP approach in the fan selection process will result in a quieter, more efficient, and more reliable system.

Talk to our highly experienced OEM team to discuss the benefits of using Rosenberg EC Plug fans from our wide range of energy efficient free running or modular centrifugal fans.