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Notes


GENERATOR SAFETY

3 Tips for Generator Safety

Generators Can Be Helpful During Times Of Natural Disaster

Disasters of any kind, natural or man made, are exactly that… disastrous and extremely costly. Let’s quickly look at what some of the worst disasters in North America have cost to clean up and fix.

Hurricane Katrina 2010 – $145B
Northridge Earthquake 1994 – $60B
Hurricane Andrew 1992 – $43.5B
Drought and Heat Wave of 1988 – $76.4B

Electricians have acquired a special knowledge that can make these disasters a little easier to bear by knowing how to install backup generators, be it portable or permanent , for just such emergencies. One must remember however, that connecting a generator directly to the wiring of a building, house or otherwise, can be dangerous if done incorrectly.

A generator directly connected to a service or sub-panel can “back feed” onto the connected power lines or other circuits attached to the sub-panel, which could in turn injure you, neighbors or utility workers.

Disconnecting Means

NEC article 445.18 states: “445.18 Disconnecting Means and Shutdown of Prime Mover. (A) Disconnecting Means. Generators other than cord-and-plug-connected portable shall
have one or more disconnecting means. Each disconnecting means shall simultaneously open all associated ungrounded conductors. Each disconnecting means shall be lockable
in the open position in accordance with 110.25.”

Enter the manual transfer switch.

transfer-switchInstallation of a manual transfer switch to safely tie a generator into a power system is a must. By doing so, you satisfy the requirement for the ability to open all associated ungrounded conductors in the sub-panel that the generator is feeding, as well as disabling the power company’s ability to feed electricity back onto the circuits currently powered by the generator, until the generator is turned off, and the manual transfer switch is returned to the non-backup position.

Transfer switches can also be locked out when they are in the OFF, or open position satisfying the requirement of article 110.25. Portable generators, like those found here , don’t have to abide by this requirement because they typically have cords plugged into them that can easily be removed from their receptacles or from a flanged inlet to which they may be connected. The removal of the plugged in cord acts as the disconnecting means.

Common sense

Article 445.10 of the NEC states: “445.10 Location. Generators shall be of a type suitable for the locations in which they are installed. They shall also meet the requirements for motors in 430.14.”

430.14 talks briefly about exhaust ventilation for motors, and NFPA 37 does as well, which is mentioned in an informational note at the bottom of article 445.10. This is where common sense comes into play. I can’t help but be reminded of a story my brother told me of a job he was working on. The power company was taking their sweet time getting the temp power hooked up, so one of the other contractors decided to bring a generator on site so they could get started. They didn’t like how noisy it was so they decided that the best place to put the generator would be in the crawl space. Can you think of any immediate reason why this would be a bad idea? If not, let me help you out a bit. Putting anything that could let out harmful fumes or exhaust in a confined space is a bad idea. One of the contractor’s employees went into the crawlspace to do some work. Needless to say,they didn’t see him for a while. In fact, they didn’t see him until they went into the crawlspace to get him. They had to drag his body out of the crawlspace because he had passed out under the house from the exhaust fumes. He lived to tell the tale, but he could have just as easily died from such an irresponsible decision.

Use your common sense when dealing with such matters.

Isolation

stand-by-generatorLast but not least is the ability to isolate one generator that may be tied in parallel with one or more other generators.

NEC article 445.18(C) States: “ 445.18(C) Generators Installed In Parallel. Where a generator is installed in parallel with other generators, the provisions of 445.18(A) shall be capable of isolating the generator output terminals from the paralleling equipment. The disconnecting means shall not be required to be located at the generator.”

To be adequately safe when you need to work on a generator that has been installed in parallel with another, you need to be able to isolate it from the others as you work on it. Another generator can and will backfeed onto the dead generator just as a utility line will back feed if the main breaker is left on or if there is no transfer switch installed.

At the end of the day, the most important thing is that you are able to go home safe to your families. Following codes and basic safety procedures will ensure that.

 

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