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Can VSDs compete with all-in-one EC fans?

30 November, 2021

Oliver Woolley, ABB’s key account manager for the HVAC sector, discusses the merits of variable-speed drives in HVAC applications, and how they stack up against electronically-commuted fans.

Electronically-commuted (EC) fans are motor-and-drive packages integrated together as a single assembly. They are an increasingly popular option in HVAC applications because of their perceived efficiency, especially at full load. Against the backdrop of sustainability and, in particular, Ecodesign regulations, EC fans might sound on paper like a compelling option. After all, why buy multiple devices (a fan, a VSD and a motor) when you can buy just one? However, any variable-speed product (AC or DC) needs to adhere to the Power Drive Systems standard EN61800-3 (PDS) to comply with the current EU EMC Regulations.

Importantly also, it is key that any integrated variable-speed product in the mechanical package is linked to the electrical requirements in your VSD specification, and that declarations of conformity are required in accordance with EN61800 for electrical safety (-5-1) and EMC (-3).

Efficiency and sustainability

Real efficiency has to be evaluated based on wire-to-air efficiency, so when a fan motor is blocking the air flow, it affects the system’s efficiency. New optimised designs mount the motor outside of the fan wheel, which does increase its size, but also improves its static head and airflow, improving wire-to-air efficiency. A key factor in HVAC systems in the global quest for net-zero targets is sustainability. Ensuring that we provide the most sustainable and efficient systems during the specification process can only help to meet these strict targets.


The most common reason for EC fan failures are the motor bearings. The life expectancy of an EC fan is around 40,000 hours, which is 4-5 years of continuous operation. In the event of a bearing failure, the whole EC fan package would need to be replaced. This can be costly, time-consuming (because of product and engineering lead times), inefficient and unsustainable for the end-user.

Engineering optimisation

VSDs pack in many more functions, with the latest generation offering superior I/O connections for building management communications, as well as carrying out the duties of other traditional panel components such as thermostats, relays, timers, safety contactors and energy management tools. Consequently, these devices are no longer needed in the control cabinet, freeing up panel space, while offering extra functions such as fireman’s override – which is exclusive to VSDs.

To learn more about how EC fans and VSDs compare, you can download a white paper from

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