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The End of the VFD Revolution: What’s Next in Outpatient Healthcare Energy Efficiency

When first introduced, Variable Frequency Drives (VFD’s) were truly revolutionary as the first practical way to take advantage of the energy savings available from variable speed motor operation. For the past 10-20 years, retrofitting constant-speed or two-speed electric induction motors with VFD’s or replacing constant-speed motors with VFD-equipped motors has been a “go-to” energy savings solution for building Heating, Ventilating and Air Conditioning (HVAC) systems.

As an industry, we are going to run out of constant speed induction motors at some time in the future. The need for energy saving solutions however, will not go away. Building owners will be turning to architects, engineers, equipment manufacturers and installing contractors to deliver the next generation of building energy optimizing technology.

A trend in the healthcare industry which will demand energy efficiency is the migration of services into outpatient and urgent-care facilities. These buildings are generally smaller and operate with fewer facilities management staff than a traditional inpatient hospital. This trend means that energy efficiency technologies will need to be more reliable, lower maintenance, and easier to use.

Three current technology types that could be part of the future of energy efficiency after the end of the VFD revolution and are well-suited to smaller health care facilities are:

  1. Non-media air filtration technologies

  2. Lighting control technologies

  3. Larger horsepower, three-phase electronically commutated motors (ECMs)

Air Filtration Technologies

HVAC fan power is a big chunk of building energy use. Fan motors consume energy to push air through all sorts of obstructions such as coils, filters, duct systems, and diffusers. The less restrictive these components are, the less energy is required. Traditional media-based filters act like a sieve to remove dust and dirt particles from the air stream, inherently restricting flow. As non-media based filtration technologies, such as electrostatic precipitators, advance, there is the potential for significant energy savings. In addition, non-media filtration usually needs less frequent maintenance as media changes are eliminated.

Lighting controls becoming more accessible, widely understood and accepted

Sunshine is free and always has been. Recent reductions in cost and widened industry acceptance of light emitting diode (LED) based lighting positions the building industry to take advantage of the free sunlight better than ever before. LED lighting, with its inherent dimmability, will likely combine with the shrinking cost and greater acceptance of lighting control technologies such as space light level sensing, multiple sensor occupancy sensors, and wireless switching. These technologies will allow more lighting systems than ever before to reduce electric lighting based on the natural light of the space, the absence of people to need that light, or both. Since lighting controls are essentially miniature computers and software, the overall trends of web-based systems, and mobile phone-style computing is also likely to speed overall acceptance of these technologies while minimizing maintenance requirements.

Larger horsepower, three-phase permanent magnet integral driver electric motors, also known as electronically commutated or ECM motors

An industry trend towards permanent magnet motors with integral drivers and controllers is already taking hold for many smaller electric motors. Presently they are commonly available at one-half horsepower and less, though some manufacturers will go as high as two horsepower in some applications. Sometimes called electronically commutated motors (ECMs) these motors inherently have a sophisticated driver that allows small motor applications to achieve all the benefits of variable speed operation previously only available in larger motors with separate and more complex VFDs. ECM motors come from the factory with optimized control sequences that make them well suited to direct drive (non-belt drive) fans and equipment. Additionally, they operate at a higher efficiency than induction type motors. These motors usually use single-phase electrical power which traditionally limits them to one-half horsepower and less to maintain building power system efficiency. Most electrical engineers prefer to see motor loads larger than one-half horsepower utilize three-phase power. As motor and driver technology evolves to allow for larger versions of these ECM motors that utilize three-phase electrical power, the efficiency and control benefits of ECM motors could be realized at motor sizes which were previously only available to induction type motors. The suitability of ECMs to direct-driven equipment can also reduce the number of belt-driven items in a building. Utilizing direct-drive ECM equipment for replacements and new equipment installations to the largest degree possible maximizes energy and maintenance savings. As commercially available ECM motor sizes increase, the upper limit of this strategy will increase correspondingly.


Building owners will be turning to architects, engineers, equipment manufacturers, and installing contractors to deliver the next generation of building energy optimization technology. Non-media air filtration technologies, lighting control technologies, and the development of larger horsepower, three-phase ECM motors are three such technologies that presently exist. They all could be part of the future of outpatient and urgent care healthcare energy efficiency after the end of the VFD revolution. What do you think? Keep the discussion going by adding to the comment section below. Special thanks to David Mayer of Greenheck and Dean Lees of Buckley Associates for their help on this blog post.


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