The U.S. Department of Energy (DOE) is empowered by congress to review efficiency regulations for covered products every five years. Electric motor manufacturers are currently operating under the Energy Independence and Security Act of 2007, which went into effect in December 2010. Around this time, the DOE started to review the regulation to see if raising the levels above premium efficiency was warranted.
Motor manufacturers that are members of the National Electrical Manufacturers Association (NEMA) discussed the potential rulemaking and decided to collaborate with energy efficiency advocacy groups and form a coalition to make a proposal to the DOE that might be easily adopted as a direct and final rule. The Motor Coalition proposed at the first DOE meeting that the efficiency levels be maintained at premium efficiency level (NEMA Standard MG 1-2011, Table 12-12, 20A and 20B) for 1- to 500-horsepower (HP) motors rather than raising the level above premium efficiency. This 12-12 level is equivalent to IE3 (premium efficiency) as defined in International Electrotechnical Commission (IEC) Standard 60034-30. Furthermore, the proposal recommended that most definite-purpose and special-purpose motors would be included along with options that previously exempted motors from coverage. During this process, some loopholes from the previous Energy Policy Act of 2005 and Extended Industry Standard Architecture (EISA) rules were also closed.
To accept the expanded scope, the DOE was required to issue a final rule on how all these motor configurations could be tested. This rule was released in late 2013. The final rule for integral HP motors was published in the Federal Register on May 29, 2014, and will take effect June 1, 2016.
The voltage range now includes all three-phase, 60-hertz (Hz) designs, 600 volts and less. Additionally, motors with special shafts and mountings along with 56-frame enclosed motors will now be covered at premium efficiency levels. Partial motors built without a drive endplate are also covered. Both NEMA and IEC motor designs are included, as are motors mounted to equipment imported to the U.S. for use here.
For the pump industry, close-coupled pump motors are categorized in the 1 to 200 HP Subpart II category. In the new rule, they change from an energy efficient level (NEMA MG 1-2011, Table 12-11) to premium efficiency (Table 12-12). Hollow-shaft pump motors and medium- and high-thrust vertical pump motors are now included at the premium efficiency level as well.
More efficient premium motors use additional active material (copper and electrical steel) and higher grade electrical steel. These materials may mean a price increase over energy-efficient motors.
Table 1 shows the differences between the EISA and the new Integral Horsepower Motor Rule.
The DOE defined a motor covered under the new rule by nine attributes:
- Is a single speed motor
- Is rated for continuous duty (MG 1) operation or for duty-type S1 (IEC)
- Contains a squirrel-cage (MG 1) or cage (IEC) rotor
- Operates on polyphase alternating current (AC) 60-Hz sinusoidal line power
- Has two-, four-, six- or eight-pole configuration
- Is rated 600 volts or less
- Has a three- or four-digit NEMA frame size (or IEC metric equivalent), including those designs between two consecutive NEMA frame sizes (or IEC metric equivalent) or an enclosed 56 NEMA frame size (or IEC metric equivalent)
- Has no more than 500 HP but greater than or equal to 1 HP (or kilowatt equivalent)
- Meets all the performance requirements of a NEMA design A, B or C electric motor or an IEC design N or H electric motor
With the new Integral Horsepower Rule, many motor configurations were upgraded to premium efficiency. These include:
- NEMA Design A motors from 201 to 500 HP
- Electric motors with moisture-resistant windings, sealed or encapsulated windings
- Partial electric motors
- Totally-enclosed non-ventilated (TENV) electric motors
- Immersible electric motors
- Integral or non-integral brake electric
- U-frame motors
- Design C motors
- IEC 100 frame, NEMA 66 frame
- Electric motors with non-standard endplates or flanges
- Electric motors with non-standard base or mounting feet
- Footless motors (C-face or D-flange less base)
- Electric motors with special shafts
- Close-coupled pump motors
- 56J Jet pump motors (enclosed)
- Vertical, hollow-shaft electric motors
- Vertical, medium- and high-thrust, solid-shaft electric motors
- Electric motors with sleeve bearings
- Electric motors with thrust bearings
- Pre-NEMA frame motors
- Arbor saw motors
Even with these added motor configurations, many motors are not covered under this rule. Some that include only general purpose NEMA frames 42, 48 and 56 with open drip-proof (ODP) enclosures are covered by the 2010 Small Motor Rule. Single-phase capacitor-start/induction-run and capacitor-start/capacitor-run along with three-phase induction motors are included at specific DOE average efficiency levels. However, the following configurations are not included:
- Single-phase ODP motors (may be covered by Small Motor Rule)
- Single-phase enclosed motors
- Direct current motors
- Two digit frames (42 \'96 48) (may be covered by Small Motor Rule)
- 56 frame ODP (may be covered by Small Motor Rule)
- Multi-speed motors
- Medium voltage motors
- Totally enclosed, air over or open air-over motors
- Submersible motors
- Water-cooled motors
- Intermittent duty motors (S2-S8)
- Stator-rotor sets
- Design-D motors
- Motors designed for inverter power (MG 1, Part 31) with no line start
- Synchronous AC motors
- Permanent-magnet rotor AC motors
- Servo motors
These DOE integral HP motor regulations apply to motors manufactured for use in the U.S. Motors built before June 1, 2016, may still be used. No restrictions were set limiting the repair or rewind of older motors below these efficiency levels.
OEMs and end users should contact their motor suppliers and prepare a plan to convert their motors to premium efficient designs if they are not already being used. Note that the performance of more efficient motors may be slightly different because they have less slip and operate at a higher speed. Impeller designs may need trimming to prevent overloading the motor from increased flow.
- CFR Part 431 Energy Conservation Program: Energy Conservation Standards for Commercial and Industrial Electric Motors; Final Rule, Federal Register, Vol. 79, No. 103, Thursday, May 29, 2014
- NEMA Standards Publication MG1-2014, Motors and Generators, National Electrical Manufacturers Association, 1300 N 17th Street, Suite 1752, Roslyn, VA, December 2014