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October 24, 2006 A Prism Business Media Publication Vol. II No. 20



CONTENTS
Maintaining Heating Systems

Electrical Troubleshooting Quiz

Replacing HVAC Blower Motors

NEC at the Facility

OSHA Misperception

Answer to Electrical Troubleshooting Quiz

North Texas Facilities Expo



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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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    Maintenance
    Maintaining Heating Systems
    Do you have a formal HVAC maintenance program, or will you simply react to failures while production workers complain about the bitter cold indoors this coming winter?

    HVAC manufacturers specify maintenance practices, but few owners follow them. Among those that employ the recommended maintenance practices, there's a tendency to treat suggested schedules as maximums. This can cause unnecessary expense and preventable discomfort to occupants. Some things to consider:

    • Perform insulation resistance tests on the blower motors (annually). For two-speed motors, check both sets of windings. When a blower fails in the summer, the condenser may ice up and not thaw for several hours. A winter blower failure may go undetected until the occupants finally complain. By the time you troubleshoot and obtain a replacement, the heat loss may be significant and result in extended indoor cold.
    • Use infrared or ultrasound regularly to nearly eliminate "surprise" motor bearing failures. Bearing failures typically result from maintenance failures -- such as improper lubrication and inadequate filter changes.
    • Understand that the recommended filter change interval is based on a "typical" application, not necessarily your application. You can inspect filters frequently, or you can automate detection by installing d/p instruments (delta pressure) across the filters.
    • When the cooling season has ended, cover condenser units so they don't accumulate winter grime. Schedule time in early spring or late winter to clean and comb the condenser fins.
    • Have a qualified person conduct the full battery of heating system inspections, if these inspections were not performed during the summer.



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    Repair
    Electrical Troubleshooting Quiz
    During several periods of deep chill last winter, the offices stayed frigid until late afternoon -- about the time people started going home. This problem first arose last year, and the system has been in service for many years. So your boss naturally concluded this must be an "electrical problem." Spring came, and other priorities took over.

    Now with cold weather approaching, the plant manager remarked that maybe the plant should issue gloves and mittens with the company logo to all office personnel -- not a good sign.

    The system uses a modern furnace with heat pump, and you can hear the furnace kick in during high demand. Is this really an electrical problem? What should you do?

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

    Replacing HVAC Blower Motors
    The primary modes of blower motor failures are:

    • Bearing loss. This is typically due to overloading from dirty filters.
    • Phase on phase shorting. Manufacturing defects (insulation deficiencies) or power quality issues in your plant are the probable causes.
    • Open conductors or connectors. Manufacturing defects or severe power disturbances are the likely culprits.
    If your blower motor is relatively new, have a motor shop do a post-mortem on it to determine the cause of failure. Yes, this motor is probably only a few hundred dollars, so a replacement is not a big budget item. But that's not the point. The point is to identify problems that may cause the remaining blower motors to fail. If you have several HVAC units, consider this step mandatory.

    If your blower motor has been in service for a long time, it's not likely you have a preventable cause of failure. But it is likely that other motors installed at about the same time will fail soon. Have replacements on hand. If there's an accessibility problem or extreme temperatures are forecast, don't wait for failure to happen. Do a post-mortem on the failed motor and then check the remaining motors for signs of a similar failure.

    For example, the motor shop tells you the insulation failed. Do an insulation resistance check on the remaining blower motors, and replace the ones that appear marginal.


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    Operation
    NEC at the Facility
    Check your enclosures for openings, such as those left by unused knockouts. Plug any that exist. [312.5(A)].

    OSHA Misperception
    Smart safety directors know there's a difference between fulfilling a "check off the box" corporate mandate and truly communicating the safety message. Make sure your safety performance reflects this same knowledge.

    Managers, take note. The goal isn't to protect your company from OSHA fines. It's to protect your workers from unsafe conditions and unsafe acts. Go beyond formal activities, and engage people on safety in the field. Ask an electrician to stop working for a moment, then ask about the safety issues involved in whatever task is at hand. Ask how that person is addressing each of those issues.

    This practice gets people "thinking safety" outside of safety training sessions. It makes it far less likely OSHA will have a reason to fine your company. But more importantly, people are less likely to get hurt.


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    Quiz Answers
    Answer to Electrical Troubleshooting Quiz Multi-stage heating systems improve energy efficiency. When the temperature differential is minor, the system uses only one stage and maintains the desired temperature. If your system has a heat pump, you might think the heat pump is stage one and the furnace is stage two. But that's not the case -- the furnace operates in a multi-stage mode (typically, two stages).

    The programmable controller or setback thermostat in your system allows the nighttime temperature to drop below what's needed for comfort. In the morning, the system tries to close a large gap between actual and desired temperatures. If it has only the heat pump and the first stage available to it, this won't happen. Most systems have an "Emergency heat" control, and you can use this to test whether the blower and furnace are getting the control signal to boost into second stage.

    You should probably get an HVAC service call authorized and have a specialist examine the system. Otherwise, you may spend time digesting the schematics and manual, only to discover you need a proprietary component.

    Now, here's where the electrical part often gets overlooked. The most likely cause of a controller failure is an unbonded grounding electrode (or connection to a discontinuous water pipe). Your system doesn't need to be grounded -- it needs to be bonded. See Art. 100 of the NEC for definitions of these key words.

    Proper bonding prevents the high potential that can produce an electronics-destroying flashover. The technician will be back for the same problem, unless you correctly bond everything.


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    Show & Events




    North Texas Facilities Expo

    The North Texas Facilities Expo will take place from Oct. 31 to Nov. 1 at Dallas Market Hall in Dallas. Seminars at this year's event include "2005 NEC Requirements for Concrete-Encased Electrodes and Other Grounding Electrodes," "Infrared Technology for Electrical Applications and Beyond," and "Who Is a Qualified Electrical Worker?" For more information, a full list of exhibitors, and to register, visit the expo's Web site.

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