electric motors

Electric Motors – Repair or Replace?

Over 50% of all the electricity used in the United States runs through electric motors. It’s clear, the decision about what to do when a motor fails in your facility is important.

Electric motors today are much more efficient than the motors manufactured before the Energy Policy Act took effect in 1997. That legislation transformed motor efficiency into a major consideration when determining whether to repair or replace.

It’s not uncommon for plant maintenance teams to have carefully created policies applying to repair or replace decisions, such as:

  • Standard motors that are 25 hp or less are cost-effective to have the bearings replaced, but not to be rewound. Motors greater than 25 hp should have the bearings replaced and get rewound if the cost to rewind is less than 60% of the new premium efficient motor.
  • For a non-standard motor, the rules are different. Taking into account the higher initial costs and potential lead times might put a greater emphasis on replacing the bearings and/or rewinding the unit. Some shops choose to rewind a motor if the cost is less than 75% of the cost of a new premium efficient motor.

There’s also an individual motor consideration: is the failed motor causing downtime to a significant portion of the plant? If so, the concealed costs could mean that the new, premium efficient motor is well worth it.

 

How Important is an Energy Efficient Motor?

 

electric motors

 

The graph above compares several motors and the average performance for a rewound motor VS a premium efficient. The final column shows the simple payback period for the added cost of the premium model.

The motors shown in the comparison are general purpose motors operating at 1800 rpm. The chart demonstrates the price and efficiency differences between a rewound motor and a premium efficient model. The final three columns provide data about whether to rewind a motor or replace it.

For instance, a standard, general purpose 10 hp motor, operating electric motors120 hours per week for 51 weeks will cost approximately $625 to rewind. A new, premium efficient version will cost $814 shipped free to your loading dock. At almost $200, it may seem that a rewind is a better decision – saves money, guaranteed fit, and more. Look further, and you will see that the efficiency of the rewound motor is 83%, but the new, premium electric motor is 91.7%.

That difference means the premium efficient motor will cost $522 less per year to operate than the rewound motor. At that rate, the simple payback period for the added expense of the new motor would be a mere four months, and from that point, your facility will save on operating costs for the rest of the motor’s service. The overall payback period for the total cost of the motor, at $814, would be 1.5 years.

 

The Importance of a Replacement Plan for Electric Motors

Even though a failed motor might be the perfect candidate for rewinding, a new, energy-efficient motor will produce significant energy savings and improved reliability. In fact, the U.S. Department of Energy recommends considering an energy-efficient model for any of the following circumstances:

  • All new installationselectric motors
  • As part of an equipment package (compressors, HVAC systems, pumps)
  • During large modifications made to facilities or processes
  • In place of rewinding an older, standard efficient motor
  • Replacement of oversized and underloaded motors
  • As part of a preventative maintenance or energy conservation program

Once your team has outlined the plan for what to do when a motor unexpectedly fails, it’s also a good idea to develop a proactive plan. A growing number of building management teams recognize the savings potential of replacing not just failed motors, but older inefficient models that are still operating.

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