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Joined: Jul 2004
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The most important part of the code is understanding when an article applies.
We are talking about PORTABLE generators not premises wiring.
250.20(B) Alternating-Current Systems of 50 Volts to 1000 Volts. Alternating-current systems of 50 volts to 1000 volts that supply premises wiring and premises wiring systems shall be grounded
NOPE
250.26 Conductor to Be Grounded — Alternating-Current Systems.
For ac premises wiring systems, the conductor to be grounded shall be as specified in the following...
NOPE
250.34(C) Grounded Conductor Bonding. A system conductor that is required to be grounded by 250.26...
NOPE
All of these refer to "premises" wiring.
When you connect a generator to a building it does require grounding the neutral but if you simply switch the phases with the transfer equipment and bring the neutral and ground straight in you use the system main bonding jumper to accomplish that.
In fact if you use a transfer switch like that you create a violation if you do have the generator grounding the neutral.
Greg Fretwell
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Joined: Jan 2004
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Greg- your right. Most portable generators hooked up via cord and plug attachment, create a code violation because the neutral and ground are bonded together on the generator in addition to the Service neutral and ground being bonded together. Unplug the generator and the violation goes away. As an Inspector it's impossible to police. George
George Little
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OK if you guys agree that an isolated neutral Generator is both safe and the proper way to be for connecting to a service, then WHY do most of them bond the neutral to ground????
No body has answered that!
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Joined: Oct 2003
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OK, some feel that a isolated system is ok for stand alone use, read the reasoning below (against that thinking)...
On a "stand-alone" (portable) generator serving cord-connected loads only, the frame is permitted to serve as the grounding electrode.
The neutral-to-frame bonding connection serves the same functions as the Grounding Electrode Conductor and Main Bonding Jumper do in a premises wiring system.
Without it, the equipment bonding conductor (EGC) in the load cords will not perform it's intended function.
Check this alert, http://labreq.lanl.gov/labreq/labreq.nsf/LookupDocNum/Alert0005/$File/alert0005.pdf
in particular the last paragraph regarding some Honda generators.
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Joined: Jan 2004
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I can only tell you what the folks at Kohler told me- It's an application issue. Depending on how you are using the generator, as a stand alone system or as part of a backup for the utility. You may or may not want the neutral conductor bonded to the frame. If they didn't include the bonding conductor then you'd have to come up with it for a Separately Derived System. By the way, you can leave the bonding in place if your going to switch the neutral.
George Little
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You are correct George about switching the neutral, but there are a great deal more transfer switches out there that do not switch the neutral. I don't even know how hard to get that one will be as it is from a canadian web site, and their code deals with this topic unlike in the U.S.
I am just trying to sort things out in my head so as friends ask me to install these, I can truthfully know I am steering them in the safest direction.
As an electrician, I back feed my whole panel from an outlet and have to manually shut off my main before doing it. I have the gen recep. locked off with the procedure hanging on it... (for my wife and myself) BUT I would NEVER hook up or recommend any other homeowner do that.
Right now my Generac 5500 Wheelhouse has the neutral bond in place. So yes I have effectively two paths back to the generator on two #8's (ground and Neutral) (Generator recep is in garage)and I bond the frame to a ground rod where I hook it up. I do not believe it provides a safety hazard it it's operating state, but I know what is there and what I am facing... Frankly, I feel that the potential is the same with the double bond and don't rightly see the hazard? Actually your service is double bonded, at your house and at the Power Co. Transformer... But again I would never suggest a friend do their's that way as it goes against the perceived standard.
I was trying to determine in my mind if leaving the bonding jumper off a Generator would be safe for stand alone use, as this would be cheaper to get a 2P transfer switch.
The bottom line is there seems to be no clear cut determination and in fact no current regulation in the USA, so I will recommend leaving the bonding jumper... (as that is factory installed) and that they pay extra for the 3P switch.
(But I still would like to hear a consensus on the gen bond for stand alone use... some say it's safe, some not... I can't place the theorey in my head on that one)
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Joined: Nov 2000
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gfretwell, We are talking about PORTABLE generators not premises wiring. In my opinion a portable generator is "premises wiring" per Article 100. Premises Wiring (System). That interior and exterior wiring, including power, lighting, control, and signal circuit wiring together with all their associated hardware, fittings, and wiring devices, both permanently and temporarily installed, that extends from the service point or source of power, such as a battery, a solar photovoltaic system, or a generator, transformer, or converter windings, to the outlet(s). Such wiring does not include wiring internal to appliances, luminaires (fixtures), motors, controllers, motor control centers, and similar equipment.
Don(resqcapt19)
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"resqcapt19
Moderator posted 01-17-2005 07:17 AM
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George,
quote:
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Hence the bonding jumper talked about in 250 for services is not applicable to generators. I'm not quite sure how youn size it.
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Look at 250.30(A)(1).
Don
IP: Logged
George Little
Member posted 01-17-2005 08:58 AM
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Thanks Don, missed that one. Interesting enough though, the size is very close to 12.5%. In fact I've heard it stated from the podium that T. 250.66 is based on 12.5%. When you do the math it's pretty close. That's what I like about this forum, what one of us misses the other one catches.
George"
YOU ARE MISSING SOMETHING HERE... 250.30 A LEADS YOU BACK TO 250.28 (D) WHICH SAYS THE MAIN BONDING JUMPER SHALL NOT BE SMALLER THAN THE SIZES SHOWN IN TABLE 250.66 (# 8 MINIMUM) THEN IT GOES ON TO ADD THAT IF PHASE CONDUCTORS ARE 1100 KCMIL OR GREATER YOU USE THE 12.5% THING YOU ARE STATING... THE MINIMUM SIZE FOR THE BONDING JUMPER IS # 8 ACCORDING TO CODE SO THE GENERATOR BONDING JUMPER OF # 12 OR # 14 IS NOT ADIQUETE!
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Joined: Jul 2004
Posts: 9,931 Likes: 34
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It is clear you do not understand the concept of an isolation transformer and safety. I quit.
Greg Fretwell
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"gfretwell
Member posted 01-18-2005 12:05 PM
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It is clear you do not understand the concept of an isolation transformer and safety. I quit.
"
Don't leave yet... let's sort this out!
According to your opinion, the gen bond is the only acceptable bond for the neutral, Right?
That said, the code sizes the Main bonding jumper according to Table 250-66 which allows for a # 8 minimum which none of these gen's have... so are they all illegal as well? Do you recommend installing a new bonding jumper? And according to you all of these isolated neutral gens are wrong as well?
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