As of March 9, general-purpose small electric motors with open drip-proof enclosures have to meet new Department of Energy efficiency requirements. The requirements apply to single-phase and polyphase motors built in a two-digit National Electrical Manufacturers Association frame and rated between 1/4 and 3 hp. Split-phase, shaded-pole and permanent-split capacitor motors don't qualify as general-purpose motors and thus aren't covered under the new rule.
The DOE asserts on its website that the new standards will result in approximately $35 billion in energy-bill savings for products shipped from 2015 through 2044 and prevent about 133.6 million metric tons of carbon dioxide from being emitted.
Long-term savings from the use of more-efficient motors aren't in dispute. But end users needing to replace small electric motors may find that their new choices in the market are larger and more expensive than the motors they're used to purchasing.
New-model motors in most cases may be slightly larger in both length and diameter than older motors because the higher efficiency specified by the DOE's new standards demands the use of more active material. Users of single-phase motors also may see some ratings change from capacitor-start–induction-run to capacitor-start–capacitor-run.
Figure 1 shows the average full load efficiency required for polyphase and single-phase motors manufactured after March 9, 2015 (or after March 9, 2017, for the small subgroup of small electric motors that require listing or certification by a nationally recognized safety testing laboratory).
For a manufacturer like Baldor Electric, preparing for the small-motor rule to take effect has meant reaching out to customers to help them understand the rule's implications in their facilities. "All of our district offices have contacted customers who had motor designs that were affected," says John Malinowski, senior industry affairs manager at Baldor.
Users dealing with significant size restraints in their machinery configuration may find that replacing an older-model motor with one of the new, larger designs is impractical, Malinowski says. In this case, choosing an enclosed motor that is not covered by the small-motor rule may be a more suitable solution at least in the short term, he says.
Challenges for OEMs and end users
Complicating the situation for users, according to Malinowski, is that the small-motor efficiency rule is the first that the DOE has constructed unilaterally. Not only are general-purpose base-mounted motors (with and without C-face or D-flange) covered, but also footless motors are covered. In addition, motors with shaft lengths outside of standard NEMA dimensions are covered. (Special-purpose shafts are not covered, as they are designed for a particular application.)
Sometimes lost in the discussion about motor efficiency is the fact that motors are one of a plant’s more durable and consistent pieces of equipment over their lifetime, and pumps, fans and compressors are equally important parts of the efficiency equation, Malinowski says.
“(Let’s say) we put a 96% motor on a very poor pump,” he says. “A better pump could use a lower-horsepower motor” and produce greater energy savings than using that 96%-efficient motor. Correct installation, too, will go a long way in helping plants maximize efficiency gains in pumps, notes Brent McManis, industry engineering manager at Baldor Electric. “You can have a huge impact on the efficiency depending on how you install it,” McManis says.
Correct installation, too, will go a long way in helping plants maximize efficiency gains in pumps, notes Brent McManis, industry engineering manager at Baldor Electric. “You can have a huge impact on the efficiency depending on how you install it,” McManis says.
Additional considerations
Beyond motor design, motor enclosures and thermals in are addressed in the DOE’s new rule.
Open drip-proof designs are covered; open air-over and enclosed designs are not. Motors using manual or automatic thermal overloads that are not UL-recognized must comply with the efficiency standards by March 9, 2015; those using thermal overloads that are UL-recognized have an additional two years—until March 9, 2017—to meet the requirements.
Important to note, too, is that motors mounted to machinery and imported into the United States are covered by the rule and must be compliant by March 9 of this year. Motors built before March 9 that are in use or that remain in inventory can still be used and sold.
“The paradigm we have to fix in energy efficiency is that we largely reward our purchasing people for saving on first cost,” Malinowski says. “The industry has got to get out of that mindset. With the cost of a motor, the purchase cost is only about 2% of its life cost; 97% is the energy used for operation.”