Circuit Breaker Maintenance
Motor System Repair Mistakes,
NEC in the Facility
Answer to Electrical
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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.
To have an effective and efficient maintenance program,
you need good written procedures. Follow these four tips to tune up
- Review for accuracy against manufacturers' recommendations and
- Review for usability, clarity, and conciseness.
- Seek and utilize user input.
- Include references to prints, manuals, and online
Lubrication should slip (that's what it does), but your
circuit breaker lubrication schedules should not. Over time, the grease
(which is the carrier for the oil) dries out and loses lubricity. Heat
accelerates this process. Pressure is another enemy of lubrication,
because you most need the lubricant in the very places where surfaces
meet and squeeze it out.
How this affects you: You depend on that breaker to open
during a fault. Lubrication deficiencies will delay operation or
What to do: Ensure your preventive maintenance (PM) program
includes the manufacturer-recommended breaker maintenance, adjusted for
You can't perform PM on breakers without de-energizing them. This is
why a maintenance bypass or dual-feed system is essential for critical
equipment. To get funding for such items, calculate the cost of not
having fault protection (including lost revenue).
It's helpful to present costs for three scenarios of outcome: most
likely, best possible, and worst. If that breaker fails, the most
outcome is the fault will destroy the supplied equipment and cabling.
The best outcome is the fault will destroy just that breaker. The worst
outcome is the fault will cause catastrophic damage, resulting in
widespread equipment loss and severe hazards to personnel.
Unfortunately, "best-outcome" scenarios are rare, but "worst-outcome"
scenarios are not.
ITC Infrared Certification and Electrical Training
FLIR's Infrared Training Center offers certification in infrared
thermography and focused training for electrical inspection. In the
Level I Thermography Certification course, you'll explore temperature
measurement, image interpretation, hotspots, and more. The Infrared
Electrical Inspection course focuses on commercial electrical systems
from the building input through switchgear, bus ducts, motor control
centers, electrical distribution panels, and breakers. Register at www.infraredtraining.com.
A 50-hp drive motor failed on line three. Before going
out to the line, you look at the PM history and pull up a graph. This
graph shows a line sloping gently downward, left to right. Suddenly,
line "breaks" into a sharp downward turn. The date is one month ago.
Ask yourself three questions:
The answers to these questions appear at the end of this
- What chart are you looking at?
- What's wrong with that motor?
- What must you do to get line three running again?
Repair Mistakes, Part 3
Skimping on "as-left" information may seem like an easy
way to reduce work overload. However, the law of unintended
produces the opposite effect. This bad habit is one reason preventable
breakdowns occur in the first place.
Two compelling reasons to take complete and accurate "as-left" data
It's easy just to check off "OK" boxes on a PM/PdM form when you're in
hurry and nothing is obviously wrong. Taking a measurement means you
have to get objective rather than subjective data. So, make sure PM/PdM
forms require filling in actual values.
- You know what changed, making it easier to solve problems the next
- You can see a change during the next PM/PdM and take corrective
action to prevent the failure from occurring.
The static (motor not running) "as-left" data should include:
The dynamic (motor running at operating temperature) "as-left" data
should include such things as:
- Input waveforms (noted as "motor de-energized").
- Insulation resistance tests.
- Alignment data.
- Condition of air filters, if applicable.
Of course, taking data takes time. Develop "as-left" requirements that
meet your needs without being such a burden that people will cheat on
data sheets. How? Update existing forms, one at a time, per the
- Input waveforms (noted as "motor running").
- Bearing temperatures (simplify to "front" and "rear" rather than
"load" and "thrust").
- Vibration, expressed in engineering units.
Save time by using digital cameras to record nameplate data. A picture
may be worth a thousand words, but it's also faster and more accurate
than re-keying information into a PDA or scribbling onto paper.
- Identify items to add (use manufacturers' guides, industry
standards, and equipment history as sources). Note why any
particular item was added.
- Have maintenance personnel review step 1 results and listen to
what they say. This increases compliance, and you get better PM/PdM
- Prioritize and select. You can't afford to have people
gathering every possible useful scrap of data, and they probably won't
do it anyway. Pare down your form to something manageable. Collect only
what is most important. Apply Pareto analysis, if you can't
It's always a good idea to use a heat gun to take bearing
temperatures. Even better, you can use a thermal imaging camera to get
an entire temperature profile.
NEC in the
Do you consider your fixed electric space heaters to be
periodic duty loads? Article 100 defines a periodic duty as
operation in which the load conditions are regularly recurrent. Heater
use recurs regularly each winter, so what would your answer be?
Answer carefully. Article 100 also defines a continuous load as one
expected to run at maximum current 3 hours or more. Whether something
runs seasonally or not is irrelevant. When it's running, your
distribution system needs to be able to carry that load. This is why
424.3(B) says branch circuits for fixed electric space heaters are
After a scorching summer, most of us are happy about
cooler fall temperatures. However, there's something uncool that
each fall. When it's crisp but not cold, people wear light jackets and
"windbreakers." These are typically made of material such as polyester
that melts into your skin if it catches fire. Don't wear such items
around electrical equipment.
Caution: "Microfiber" is polyester. Wear a jacket suitable
electrical work or no jacket at all. You can find proper apparel
wherever electrical supplies are sold.
Electrical Troubleshooting Quiz
- It's the winding insulation resistance chart,
trended over time.
- That downward break in the slope means the insulation has
accelerated its normal deterioration, and a problem is going to happen
- This motor has a failed winding. For this size of motor, that's
rarely a "repair-in-place" situation. Thus, the motor needs to be
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