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May 20, 2008 A Penton Media Publication Vol. IV No. 10

The Power of Information -- Take 2

Motor Maintenance Tip, Part 13

Electrical Troubleshooting Quiz

Circuit Breaker Repair Tips

Sizing Fuses

NEC in the Facility


Learn About the Changes in the 2008 National Electrical Code

Answer to Electrical Troubleshooting Quiz

About This Newsletter
This twice-a-month
e-newsletter is brought to you from the publisher of EC&M magazine.

MRO Insider addresses topics such as:

  • Working with management and supervision
  • National Electrical Code® on the production floor
  • Safety procedures and programs
  • Troubleshooting techniques
  • Equipment maintenance and testing tips
  • Managing motors and generators
  • Trends in training and education
  • Managing energy use

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    The designations "National Electrical Code" and "NEC" refer to the National Electrical Code®, which is a registered trademark of the National Fire Protection Association.




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    The competition has honored innovation and excellence in product development in the electrical industry for the past seven years.

    The Power of Information -- Take 2
    The previous issue of MRO Insider looked at some types of information you can use to make your maintenance system truly effective. Your system should also have the following information for each piece of equipment:

    1. Maintenance procedures and schedules. Base these on the manufacturer's recommended practices. Also see the relevant industry standards, such as NFPA 70B, Recommended Practice for Electrical Equipment Maintenance and NETA's Maintenance Testing Specifications.
    2. Maintenance history information. This includes dates of installation, inspection, repair, modifications, and upgrades. Be sure it provides details as to what was done, who did it, and what test equipment was used.
    3. Maintenance test and inspection records. This should include the following data: as found, as left, trending, and analysis.
    In the next issue, we’ll examine three information sources that help make maintenance cost-efficient: better maintenance, same budget.

    Motor Maintenance Tip, Part 13
    When a motor is restarted too frequently, you have overcycling. This is a problem because the resultant excess heat dramatically shortens motor life. Good maintenance focuses on preventing root causes of failures, such as overcycling.

    But if you have a temperature monitoring system, can’t you just let it tell you if there’s a problem? Wouldn’t that simultaneously increase output and eliminate the hassle of enforcing cycle times administratively? No. The fly in that particular ointment is this: Temperature is an inherently slow process variable to monitor. By the time the instrumentation can reveal an overcycling condition, the damage is already done.

    Temperature monitoring, while highly beneficial, isn’t an overcycling protection system. The purpose of temperature monitoring is to reveal abnormal spot temperatures during normal operating conditions. With that information, you can schedule preventive repairs.

    For maximum uptime, supplement the temperature monitoring system by periodically performing thermal imaging on critical motors. Today’s thermal cameras make accurate temperature reading easy and inexpensive. If there’s a discrepancy, you can schedule a calibration of the monitoring system. Or, if the thermal image shows a hotspot you’re not monitoring, you may add more data points to the system.

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    Electrical Troubleshooting Quiz
    Your facility has three similarly constructed conveyor systems that carry similar loads. Occasionally, they jam and stop. The operators are supposed to clear the jam, wait for 5 minutes after the motor stopped, and then restart the conveyor.

    In reviewing the maintenance logs, you notice the drive motor for Line Two has been replaced four times as often as the drive motors on the other two lines. It always fails during the second shift or shortly after the third shift begins. You suspect the second shift operator is overcycling the drive motor. However, the temperature monitoring system shows only slightly high temperatures. How can you determine what’s going on?

    The answer to this question appears at the end of this newsletter.

    Circuit Breaker Repair Tips
    Circuit breaker repair or replacement usually involves a tight window of time. Running into problems during that window can force you into an incomplete or delayed repair. Address those problems ahead of time. For example:

    • Do you have the cranking and racking tools for each model of breaker, and are they in good condition?
    • Do you have the proper lifting brackets and equipment?
    • Do you have power and lighting you can use when shut down?
    • Do you have the recommended spare parts?
    If the answer to any of the above questions is "no" for any critical breaker, then you have some cost-saving, outage-shortening work to do. But it won’t save you money or shorten an outage if you wait until you’re in an outage to do it.

    Sizing Fuses
    Generally, but not always, you should size a fuse at 125% of the noncontinuous load. See the following NEC Articles:
    • Services: 230
    • Feeders: 215
    • Branch Circuits: 210
    • Motors: 430

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    NEC in the Facility
    If you have a multi-section motor control center, the sections must be bonded together. You’ll see the word “grounding” in the subtitle of 436.96 where this requirement is found. But here the NEC means “bonding.” Don’t drive a ground rod at each section to achieve an equipotential plane, because driving rods won’t produce that result. Use an equipment grounding (bonding) conductor or equivalent grounding (bonding) bus sized per Table 250.122. See the Art. 100 definitions of bonding and grounding.

    You’ve undoubtedly heard “knowledge is power.” When it comes to your personal safety, this is especially true. You give yourself the power to prevent injuries to yourself or others when you learn and follow the safety policies and procedures applicable to your work and your location.

    Sometimes, the policies and procedures are updated to be more stringent. Some people, confronted with new rules, think, “I was perfectly safe with the old rules, so these new ones don’t apply to me.” What they fail to realize is that management is applying “lessons learned” from someone else. Often, those lessons result from actual injury or death at another location. Updating the existing policies can help you apply those lessons and avoid a similar fate, but only if you follow the updated policies.

    Show & Events

    Learn About the Changes in the 2008 National Electrical Code
    In two informative and interest-filled days with Mike Holt, you'll learn about major NEC changes that will impact your work, whether you're an electrician, contractor, engineer, designer, or plant/facility maintenance person. You'll also earn continuing education hours and professional development hours.

    Two conferences are scheduled for 2008:
    --September 4-5 in Portland, Ore.
    --September 8-9 in San Antonio
    For more information and to register online, go to

    Quiz Answer
    Answer to Electrical Troubleshooting Quiz
    The temperature monitoring system could easily be averaging out the temperature readings, due to where the temperature sensors are placed and the fact that temperature is a slow-responding process variable. You can overcome part of this issue by using a thermal camera to get a more detailed view of the motor. A hotspot that would “average out” at the sensor will show up in the thermal image.

    To determine if the motor is being overcycled, watch the operator. If it’s not being overcycled, then you need to send the next failed motor to a motor shop for forensic analysis so you can determine what problem you are really facing.

    If it is being overcycled, you have an application mismatch. Five minutes is a long time for operators to wait. Examine the application for the practicality of ducting in air to cool the motor. Is the motor of the right insulation rating? Contact the manufacturer to discuss how you can shorten that waiting time to something the operators can live with.

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