Circuit Breaker Maintenance
Common Repair Mistakes, Part
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.
Review your PM system to see if it conforms to the
overall purpose of the maintenance department -- the typical PM
What is your overall purpose? You may be surprised to learn that
not to prevent downtime. The goal of any maintenance department is to
protect the revenue stream. Implicit in this, of course, are the
requirements of protecting the facility and the people in it.
Each piece of equipment makes a different level of contribution to
the revenue stream. Thus, each deserves a different level of
attention. Focus on completely maintaining the most critical systems
equipment. Systems are "most critical" in this order:
For systems and equipment of lesser importance, production managers
have to decide what rate of failure is acceptable and what maintenance
resources they will pay for to get there.
- Those that protect people, the environment, or the facility (e.g.,
fire protection systems). Allow no compromises.
- Common systems on which the facility depends for operation (e.g.,
service entrance and main feeders).
- Those that produce the highest revenue or handle critical
accounts. The production managers know exactly which are which, here.
Get this information from them.
Don't put yourself in the position of saying you "tried" to keep
everything running when something critical fails. It's better to lose
$3,000 on an auxiliary production line than to lose a $20 million
customer because chronic power quality problems once again caused a
Don't let individual department managers sway you, no matter how
loudly they complain. Have your plan reviewed and approved by the plant
manager and by the production managers as a group. Let them work out
must take a hit and who can't take one.
Experts advise following the manufacturer's maintenance
recommendations. However, those same experts (and manufacturers) are
quick to point out that those recommendations assume certain things.
Although many customers see these recommendations as "targets" that
are costly to meet, the reality is the opposite. Operating conditions
other factors render the manufacturer's recommendations less than
adequate in many applications. This is why breaker manufacturers advise
customers to make adjustments for environments with high levels of
humidity, or dirt.
The manufacturer's recommendations are a starting point. Avoid the
"check-off-the-box" mentality. Instead, determine what's needed to
ensure your breakers work when you need them to. It's not about what
can get away with -- it's about what loss of property, life, or
operations you can prevent.
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A motor drive fails, and you look up its repair
You notice it's failed several times over the past two years. On the
bright side, the repairs take half as long as they did a year ago.
What's wrong with this picture? What should you do?
The answers to these questions appear at the end of this
Mistakes, Part 2
Maintenance techs that perform certain repairs often
know exactly what to do the next time a line goes down. But being
efficient at restoring equipment to operation is not the same as
The culture in many facilities rewards ineffectiveness. Here's the
Though costly, this pattern is typical. People are rewarded for solving
problems, because problems bring stress.
- Equipment breaks, production stops.
- A maintenance tech rides in on a white horse, six-shooter in
- Shortly thereafter, production lines are up again.
- The tech rides off into the sunset, while admiring production
supervisors look on.
Preventing problems prevents the stress that comes with them, so the
emotional rewards aren't evident. From a larger financial and
competitive viewpoint, it's far better to prevent problems than to fix
them. Nevertheless, that's not the viewpoint many people operate under
in nitty-gritty daily life.
Compounding this paradox is the fact that repair techs are under
pressure to get things running again, and every minute counts. The one
who satisfies the immediate need looks better than the one who does a
thorough job. This affects raises, promotions, training slots, and
perquisites. The "slower" tech loses, even when preventing the problem
from ever happening again.
How can you correct this quandary? If you're a maintenance tech
rather than a manager, you may feel powerless. But you aren't. What you
must do is document the dollar value of correcting the root
cause. Talk with a maintenance supervisor to get the revenue per
hour on that machine. Then, incorporate that dollar figure into your
repair report or trouble ticket. To ensure your supervisor understands
the value of your contribution, ask what the annualized value is of
If you're a maintenance manager, don't wait for repair techs to take
the step just outlined. Insist on it for every repair. This also helps
you clearly see where maintenance dollars are being spent effectively
NEC in the
When you size the overcurrent protection devices
for motor circuits, a kind of reverse logic applies and it's
confused. Article 430 provides a tool that, if used correctly, will
prevent that. Perform your motor calculations in the order shown in
Figure 430.1, rather than in the order in which the requirements appear
in Article 430.
Industrial-grade DMMs come with many safety features.
However, no design can protect you from unsafe use. Unfortunately,
who misuse DMMS usually don't know they are doing so. Don't assume you
know test equipment safety rules just because nothing has happened to
Electrical Troubleshooting Quiz
There are several things wrong with this picture. First
of all, today's drives are very reliable. When they do fail, it's
usually for a reason that has nothing to do with the drive itself. So,
repairing or even replacing the drive is usually an ineffective
Your first step should be to assess the drive environment:
If you find and correct problems in the drive environment, you're still
not home free. Go through the manufacturer's recommended
steps, which can be found in the product manual.
- Put a power analyzer on the incoming power.
- Inspect the system for proper bonding. See Article 250, Part V and
IEEE Standard 142 (The "Green Book").
- Conduct insulation resistance tests on all cabling in the motor
system and on motor windings.
- Check the load.
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