Maintenance for energy efficiency is really a subset of thorough maintenance for reliability. Review your power supply maintenance program to ensure it's complete, and you'll have both bases covered. Once you've eliminated energy losses in your power supply, you can turn your attention to saving energy in your power distribution system. This topic will be addressed in the next newsletter.


Repair
Electrical Troubleshooting Quiz
Your power monitor is set up to show the voltages at the load end of each feeder. Your supply is 484V. You have 10 feeders. All of them are within 2% of supply voltage, except two -- those are at 448V and 443V. What might be the cause?

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


Energy Repairs
Transformer replacement offers potential energy savings. Before ordering a replacement transformer, calculate the total load. Use the method appropriate for the type of circuits being supplied (service, feeder, branch). Then, select the transformer size that most closely optimizes efficiency.

Characterize the load -- is it mostly linear or nonlinear? Would it make sense to split some of this load up and buy two transformers? You might want to do this if, for example, 20% of the load consists of resistive heaters and 80% consists of motors.

These are just some of the considerations in proper transformer selection. Careful selection can turn an equipment failure into energy cost-savings.


Operation
NEC at the Facility
You might be surprised if you inspect your bottom-fed panels. Anytime a raceway enters a switchboard, floor-standing panelboard, or similar enclosure, it has to allow sufficient space for NEC-compliant installation of the conductors.

If raceways enter the enclosure below the busbars (or their supports or other obstructions), they must allow conductor clearance of 8 inches for insulated busbars and 10 inches for uninsulated busbars. In any case, raceways can't rise more than 3 inches from the bottom of the enclosure [408.5].


Confined Entry Attendants
Remember the old Maytag repairman commercials? That's kind of what a confined entry attendant's job is like, most of the time. This can lead to some false assumptions.

The attendant may falsely assume that the attendant job involves doing nothing, or that the work inside the confined space is just routine. Either assumption can lead to inattention and poor preparation.

The person going into the confined space may assume the attendant is familiar with the permit, but this may not be the case. Always review the permit with the attendant. Note if extraction gear is required, what monitoring duties the attendant has, and what the communication means are.


Show & Events
Let's Go Racing! Win a free Road America race weekend for two.
EC&M magazine and Generac Power Systems have teamed up to offer an expenses-paid weekend (August 10-12, 2007) featuring two of the world's fastest racing series. The third annual Generac Power Weekend is one thrilling day of American LeMans series racing (the Generac 500) and an equally exciting day of Champ Car racing at its finest (the Generac Grand Prix). It's your chance to see both series compete in a single weekend at one of North America's most beautiful tracks. Located in the hilly heart of Wisconsin's scenic Kettle Moraine area, Road America is a 4-mile permanent road course that tests drivers with 14 challenging turns.

Enter by July 10, 2007. Visit the Generac Power Systems virtual booth at the EC&M E-Tradeshow. Full contest rules are available online in the Generac E-Tradeshow booth. For more information about the Generac Power Weekend, go to www.roadamerica.com.


Quiz Answers
Answer to Electrical Troubleshooting Quiz First, you'll need to perform voltage drop calculations. Voltage drop is the calculated (not measured) loss due to resistance of the wire over a distance. If your calculations show excessive voltage drop (see 215.2(A)(3) FPN No. 2), you need to replace the cables with larger ones and/or distribute at a higher voltage for a longer distance.

If you have a large difference between the calculations (voltage drop) and measurements (voltage loss), you have either cable leakage or a potential across connections. You can use infrared, split cable tests, or other methods to locate bad cable sections or bad connections. It's more efficient to test an entire feeder and repair all problems than to shut down and repair just the worst connections or cable sections. But time and money may constrain you to do only partial repairs.