NEMA Premium® Motors Help Deliver Extra Cost Savings Taking a total-cost-of-ownership approach to motor replacement can result in significant savings

The Department of Commerce estimates that there are more than 12.4 million electric motors larger than 1 hp in service throughout industry in the United States, and that nearly 3 million of these workhorses will fail in the next 12 months. The chances are good that you’ll face the prospect of selecting the right motor to replace a failed unit sooner rather than later. You also should evaluate the economics of replacing all the motors in your operation to help save energy and contribute to improvements that are environmentally friendly.

Compared with other equipment, an electric motor is an exceptionally reliable device. It’s not unusual for a properly installed motor to achieve its expected lifetime of 20 years to 30 years. That leads to an interesting fact. The cost of the energy a motor consumes during its useful life is many times the motor’s purchase price. Studies have shown that a motor’s purchase price represents just 2% of its lifetime cost, whereas the electricity it consumes accounts for more than 97% of the life-cycle cost.*

This clearly indicates that total life-cycle costs are the right way to evaluate the replacement of a motor and its selection. Also, there are several governmental regulations to consider in the selection process, as well as opportunities for tax credits and utility rebates that may affect your decision. With this in mind, let’s take a look at the options you have for replacing a motor, whether it’s serviceable, sick or failed.

Choose the right efficiency If a high efficiency motor (EPAct) is still in serviceable condition and was installed before Dec.2010, when the E.I.S.A Federal Legislation came in force, you might choose to rewind it rather than replace it. In general, rewinding a motor costs about 40% of the purchase price of a new unit — a reasonable savings.

But, the Department of Energy (DOE) indicates that even best-practice rewinding brings a penalty in operating efficiency. The rewinding process raises the amount of energy consumed and, therefore, the motor’s operating cost during its remaining life. The DOE suggests that motors smaller than 70 hp should be replaced, not rewound.

If a motor is beyond repair and rewinding, you have several replacement options to consider. Because E.I.S.A grandfathered in definite-purpose motors (motors that have been built for a specific application such as a pump or a compressor) that were installed before 2010, you might be able to replace your motor with a new custom-built standard efficiency unit. In this case, you’d expect the same ongoing energy cost profile during the next two or more decades. Remember, however, that electricity costs have been rising during the past five years and this trend is expected to continue.

As an alternative, you should consider a NEMA Premium efficiency motor that meets the current EISA efficiency standards that came in force in December 2010.

Their cost premium of less than 10% compared to high efficiency motors is offset by their 1% to 4% better operating efficiency within a couple of months (Table 1). In fact, the reduction in energy usage, on average, will pay for the entire motor within a few years or

even months and continue to deliver additional savings during the two decades or more of useful life you might expect from the motor.

Size (hp) EPAct NEMA Premium 5 88.2% 90.5% 10 90.0% 92.2% 15 91.0% 92.6% 20 92.6% 93.4% 25 93.1% 94.0% 50 93.9% 94.5% 100 94.1% 95.0%

Table 1. Average efficiency (at 75% load) for various sizes of standard efficiency, EPAct and NEMA Premium motors

You should always consider the option of replacing a motor rather than rewinding it. In order to make this decision easier you can use a “Return of Investment” calculator available at www.weg.net/green .

If you are truly concerned about energy savings, operate a factory with a good number of electric motors, and several of your applications are variable torque such as pumps and fans there are even more options you might want to consider such as installing variable frequency drives for those application that do not need to be running t full speed all the time. As well, there are new lines of electric motors such as the Super Premium Efficiency which offers efficiency levels higher than NEMA Premium. There are also lines of motors that use new technologies with permanent magnets that deliver efficiencies close to 100% and are capable of direct-on–line starts without the need of a special starter or a drive.

Utilities and state and federal energy regulators have several programs in place that make these alternatives even more attractive. These combinations of rebates, tax incentives and cost-sharing programs vary by state and municipality, but all of them can be substantial, significantly reducing the payback period for energy-efficient motors and taking additional actions. These incentives are inducing a number of companies to replace perfectly serviceable motors with higher efficiency units as part of green initiatives that help improve a company’s brand positioning in the marketplace.

Calculate the Savings Calculating the potential savings from replacing a standard efficiency motor with a NEMA Premium unit is straightforward:

Savings = 0.746 x hp x hr x rt x (1/Eo – 1/En)

Where: hp = motor size (in horsepower) hr = operating hours per year rt = utility rate in $/kilowatt-hour

Eo = efficiency of the existing motor (decimal fraction) En = efficiency of the replacement motor (decimal fraction)

Replacing a 100 hp standard efficiency motor (Eo = 0.936) that runs 8,000 hours per year with a 100-hp NEMA Premium motor (En = 0.95) will result in an annual energy savings of more than $750 when a kilowatt-hour costs $0.08.

Savings = 0.746 x 100 x 8,000 x 0.08 (1/0.936 – 1/0.95) = 47,744 x (1.06838 – 1.05263) = 47,744 x (0.01575) = $751.97 per year

Clearly, this would help cover the motor’s cost premium in a few months and the entire cost in a few years, while producing significant savings in lifetime costs beyond that.

Nevertheless, simply replacing a standard efficiency motor with an alternative doesn’t guarantee reduced electricity bills. Factors such as duty cycle, motor oversizing, unbalanced phases and other application variables can reduce the potential savings. Always consult with your motor OEM or distributor to determine the exact savings to expect.

Consider the future To help maximize the economic benefit from your motor-replacement choice, the Industrial Efficiency Alliance (IEA), a nonprofit organization dedicated to making energy efficiency a core business value, suggests establishing a continuous energy improvement program. The first step in such a program is to appoint a motor system champion who has the training and authority to make decisions about future motor purchases. The champion should conduct a comprehensive motor management assessment or energy audit to gather appropriate data about the motors installed in your plant. Using this data, your champion can advise plant management about ways to improve motor purchasing, rewinding and maintenance issues. In addition, the champion can work with qualified vendors and contractors, as well as utility representatives, to optimize the motor system efficiency throughout the plant.

If you aren’t currently evaluating NEMA Premium or more efficient motors as replacements for failed or functional standard efficiency motors, you’re probably leaving valuable dollars on the table. The IEA estimates that a dollar saved on energy, maintenance and production is equivalent to $17 in sales revenue having a 6% gross margin.

Further, the DOE estimates indicate that switching from standard efficiency motors to NEMA Premium Efficiency motors could help save our economy more than $10 billion annually and reduce carbon emissions by nearly 80 million metric tons — the carbon equivalent of taking 16 million vehicles off the road. That’s not only good business — it can make a real environmental difference.

* The remaining 1% is made up of other expenses such as rewinds, re-greasing, etc.

Grainger offers a wide variety of NEMA Premium® motors including those manufactured by WEG Electric Corporation. Several online calculators are available to help determine anticipated cost savings when choosing high efficiency motors.

For more information, visit www.grainger.com/green