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Main breakers in Generator panels


mgbinspect
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Here in Richmond, probably 8 out of 10 sub-panels for generators don't have that special linkage that makes it impossible to receive current from two sources at the same time or back feed into the main system and fry some poor power company lineman.

I'm wondering:

1. Is that actually required by code?

2. Can a couple of you electrical gurus offer some good terminology for identifying the condition and recommendations for a remedy.

3. What is the proper name for that main breaker linkage or assembly?

This is one I always more or less fumble through. I always call it out. I just wish I had a good authoritative statement and remedy. Help?

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The code (NEC 2002), Article 445.18, says

"445.18 Disconnecting Means Required for Generators.

Generators shall be equipped with a disconnect by means of which the generator and all protective devices and control apparatus are able to be disconnected entirely from the circuits supplied by the generator except where:

(1) The driving means for the generator can be readily shut down; and

(2) The generator is not arranged to operate in parrallel with another generator or other source of voltage."

1. From the above, I don't see a requirement. But that's only one paragraph, and , i may be looking in the wrong place.

2.I do not have any standard verbiage for the condition you cite (rarely see generators here in NW Georgia.)

3.Now If that linkage is not called a transfer switch, I don't know the answer to question 3 either.

(eediteed fer pore speeling)

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I'm no electrical guru, but I do see quite a few generators out here.

1. For residential, it is referred to as "Optional Standby Systems" if you want to look up a reference. It will say something about it being required to have transfer equipment installed to prevent inadvertent interconnection of normal and alternate power supplies.

3. In the absence of a transfer switch, there should be linkage between the main breaker and the generator breaker called a "breaker interlock mechanism".

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Originally posted by mgbinspect

Here in Richmond, probably 8 out of 10 sub-panels for generators don't have that special linkage that makes it impossible to receive current from two sources at the same time or back feed into the main system and fry some poor power company lineman.

I'm wondering:

1. Is that actually required by code?

Abso-freaking-lutely. As Bill said, it's in the section on optional standby systems, Section 702.6.

2. Can a couple of you electrical gurus offer some good terminology for identifying the condition and recommendations for a remedy.

The generator lacks a transfer switch. Without this important safety device, electricity from the generator can travel backwards on the utility power lines. Linemen who might be trying to repair these lines could be killed by this improper installation.

A secondary concern is that, without a transfer switch, certain circuits in your house could receive power from both the power utility and the generator at the same time. This could damage appliances and might even start a fire.

Have an electrician install a transfer switch.

3. What is the proper name for that main breaker linkage or assembly?

This is one I always more or less fumble through. I always call it out. I just wish I had a good authoritative statement and remedy. Help?

It's called a transfer switch. There are several different kinds.

- Jim Katen, Oregon

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Thanks Jim, I was hoping you'd chip in. So, to be perfectly clear. The "transfer switch" is the assembly or linkage that forces one breaker to be in an "off" position in order to permit the other to be in an "on" position?

That's the heart of my second question.

I can't believe so many electricians around here don't install them! It's mind boggling. And, I see more generator panels every day here. I always think to myself, "How many homeowners have any idea at all what needs to be done when the power goes out and they plug in that generator?" There never seems to be any manual or instruction plate handy. I think that should be a requirement as well, to have some sort of instruction plate similar to the one chained to a metal prefab gas log fireplace.

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Originally posted by mgbinspect

Thanks Jim, I was hoping you'd chip in. So, to be perfectly clear. The "transfer switch" is the assembly or linkage that forces one breaker to be in an "off" position in order to permit the other to be in an "on" position?

A "transfer switch" is a switch that transfers incoming power from one source to another using a single switch that's designed for that purpose.

There are also things called "transfer panels." These use two regular circuit breakers with an interlock device between them that only permits one of the breakers to be in the "on" position at a given time.

As far as I know, either set up will fulfill the requirements of 702.6. That section refers only to "transfer equipment."

That's the heart of my second question.

I can't believe so many electricians around here don't install them! It's mind boggling. And, I see more generator panels every day here. I always think to myself, "How many homeowners have any idea at all what needs to be done when the power goes out and they plug in that generator?" There never seems to be any manual or instruction plate handy. I think that should be a requirement as well, to have some sort of instruction plate similar to the one chained to a metal prefab gas log fireplace.

That's interesting, I see a lot of generators too, and I can't remember ever *not* seeing some type of transfer set-up. Some have been pretty bogus, but at least there was a nod toward the issue. The better installations do, indeed, include an instruction panel as you've proposed.

For a real kick in the pants, check this out:

http://cgi.ebay.com/GENERATOR-EXTENSION ... dZViewItem

- Jim Katen, Oregon

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I'll have to study my next generator panel harder to be sure. It just seems that most of them aren't as idiot proof as they should be. They require knowledge and deliberation. Not a good idea when the new home owner probably lacks the knowledge to be deliberate!

Not to mention, I can only guess that being accidentally tapped into the main entry when the system's down would fry a generator pretty quickly.

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