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December 23, 2008 A Penton Media Publication Vol. IV No. 24

Maintaining for Energy Savings, Part 4

Electrical Troubleshooting Quiz

Prioritizing Repairs

NEC in the Facility


Answer to Electrical Troubleshooting Quiz

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MRO Insider addresses topics such as:

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    Maintaining for Energy Savings, Part 4
    Correcting power factor and installing variable drives reduces energy waste in air-handling systems. To push system efficiency further, answer these two questions:
    1. Are you using all of the air you’re pushing?
    2. What load are you pushing against?
    Pushing conditioned air into spaces where it’s not used (e.g., above the ceiling) means your system must condition more air to maintain the desired temperature and humidity. Duct leakage is the primary cause of this waste. Ductwork can leak at every joint, and often those joints aren’t readily accessible.

    In older facilities, one “solution” to excessive leakage is to “upgrade” to larger air handlers (e.g., replace a 15-ton unit with a 20-ton unit). The resulting mismatch between blower output and ductwork capacity lowers efficiency and nearly always degrades temperature regulation.

    Rather than oversize the blower, reduce the leakage. Due to accessibility issues, performing a comparative flow analysis to determine the leakiest runs is a recommended approach. Where you have access to the ductwork, however, you can use your thermal camera to spot exact locations of leaks — a job made easier during the heating season. Fixing just these leaks is a fast, inexpensive way to get results. It might even make the other work unnecessary.

    Now, what about that second question? Where a system has high back pressure (load), the culprit is almost always poor filter maintenance. Keeping filters clean also reduces duct pressure ahead of the filter and thus reduces upstream leaks.

    Question: How do you know when to change air filters?

    Answer: Set up pressure monitoring across the filters and tie this to your building management system for an automated alert.

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    Electrical Troubleshooting Quiz
    Over the past few weeks, you’ve received numerous complaints about “nuisance breaker trips” from office personnel. The affected circuits supply employee workstations in various departments, such as accounting and customer service. Each time you go to examine the affected panels, you discover “someone” reset the breakers before you got there, making this a safety problem as well.

    The facility has a power monitor watching the feeders, and no anomalies appear in the logs. You took some voltage measurements at a few receptacles and found things to be normal. Why are those breakers tripping?

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

    Prioritizing Repairs
    Equipment never breaks down on a set schedule or in an orderly fashion. Some days, it seems everything breaks at once. On those days, what do you fix first?

    Set your equipment priorities based on plant safety and revenue flow. Your safety-related systems and equipment are clearly identified (or should be), so what about revenue flow? What exactly is that?

    A production plant makes revenue by shipping product. Work In Progress (WIP) flows through the plant the way water flows through a piping system. Every plant has certain “pipes” through which everything must flow.

    At some point in the system, a particular pipe limits flow though the entire system. Elihu Goldratt (author of “The Goal,” an operations management book) refers to this pipe as “the bottleneck.” When you have to choose what to repair first, safety comes first. Next in line are those revenue-restricting bottlenecks.

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    NEC in the Facility
    A site can contain both Class I and Class II locations. Confusing the two can be easy, so take care that doesn’t happen.

    The seal requirements for Class I locations [501.15] are more detailed and extensive than those for Class II locations [502.15]. The difference is this: Class I addresses the presence of combustible (or flammable) vapors, while Class II addresses the presence of combustible dust. It’s much harder to control vapors than dust, so Class I requirements are more stringent than Class II. If the location has vapors, apply Class I.

    Even legal drugs can have catastrophic consequences in electrical work. You don't want to be slow to react or hyperactive when working on live circuits or equipment. Some common examples:

    • Antihistamines. If the label says it “may” make you drowsy, don’t take it before or during work.
    • Decongestants. Typically, a decongestant speeds up your entire system. Its effects are comparable to those of other stimulants, such as coffee or diet pills.
    • “Energy” drinks (e.g., Jolt, Red Bull). It’s safer to overcome “the drowsies” by going to bed earlier rather than by caffeine overload.
    What should you do?
    • Always read the label and use as instructed. If in doubt, ask a pharmacist.
    • If you’re taking other medications, ask a pharmacist about drug interactions.
    • If you’re on any medications, let your supervisor know. If something happens and you’re unconscious or incoherent, this information may save your life.

    Quiz Answer
    Answer to Electrical Troubleshooting Quiz
    The timing is a good clue. We’re now into winter, so don’t be surprised if you see personal space heaters tucked under desks.

    One downside of “going green” is that some companies embrace it by lowering thermostats too far. No longer kept warm by an efficient central heating system, occupants resort to point-of-use heaters and often supplement them with small coffee makers. This typically results in a rat’s nest of daisy-chained surge strips and extension cords.

    What about the nuisance trips? Count up all of the loads on each circuit (including coffeemakers kept in desk drawers), to determine which breakers are being overloaded. These should be tripping — replace any that aren’t. To correct the overload, you must correct the underlying problem.

    One choice is to add more circuits to accommodate the heaters and other devices. Another is to simply turn up the thermostat. The first choice will require an investment in labor and material, and it will be more energy-consumptive than achieving the same effect per the second choice. Management needs to decide if it wants the appearance of green based on an unrealistic thermostat setting, or if it wants to actually be green.

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