Grounding a Portable Generator

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Old 11-09-13, 08:16 AM
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Grounding a Portable Generator

I read this old post and understand I need to break the neutral bond on my generator but I'm trying to understand if my Generator really as a neutral bond. I started the post below. If any of you know how to tell, I'd appreciate it.

http://www.doityourself.com/forum/el...d-neutral.html
 
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Old 11-09-13, 11:20 AM
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Note that a neutral switching transfer switch will not correct the problem of neutral and ground bonding both at the generator and in the panel.

I strongly discourage unbonding neutral and ground at the generator if this is not sanctioned by the manufacturer. Instead, unhooking and taping off the green wire somewhere along the path between the generator and the transfer switch would be a better choice, but might not be needed either if the generator runs properly when hooked up.

If neutral and ground can be readily unbonded at the generator, the bonding can be put back in place for using the generator away from buildings and building electrical systems.

A generator not connected to a building electrical system may be connected to a building ground rod if this is more convenient than driving a separate ground rod.
 
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Old 11-09-13, 02:23 PM
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Note that a neutral switching transfer switch will not correct the problem of neutral and ground bonding both at the generator and in the panel.
I disagree. A properly installed neutral switching transfer panel OR a neutral switching transfer switch and auxiliary panel most definitely WILL correct the problem of the neutral-equipment ground bond at two places. However, this cannot be done with the use of a circuit breaker interlock device.
 
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Old 11-09-13, 05:37 PM
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Thanks for the feedback guys. I assume ALLANJ is stating a normal 2 pole transfer switch will not break the neutral bond on the generator and FURD your indicating a 3 pole transfer switch will definately break the neutral bond at generator. I believe your both correct.

Since I want an interlock versus a transfer switch, is it perfectly safe and code compliant to use the interlock on the main panel and break the bond on the generator? I prefer to have the flexibility to switch other breakers on and off during a power outage to control what needs power. Also, I think most 3 pole transfer switches are much more costly. I do plan to have my Electric companies Electrician install the interlock because of liability issues but he never seemed concerned about the neutral bond issue. I want to ensure it's safe and code compliant. So this is why I ask if it's safe and code compliant to use the interlock on main panel which is bonded and remove neutral ground on generator to make it float? Appreciate your help.
 
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Old 11-09-13, 08:37 PM
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Quite honestly, it is all but impossible to connect a portable generator to a premises wiring system in a fully code approved manner. This has to do with the rules for bonding, grounding and disconnecting means. The best method is with a switch that interrupts ALL conductors, grounded and ungrounded thereby making the generator a "separately derived source" apart from the utility.

Keep in mind that the only "approved" (by a NRTL) interlock device is one that (a) cannot be defeated by removing the panel cover, and (b) one that has been submitted to a NRTL along with the specific panelboard for testing and approval. These approved interlocks are mostly made by the manufacturer of the specific panel. Most aftermarket interlocks are NOT "approved" although they may state that they are designed and constructed in accordance with NEC and UL specifications. Some jurisdictions do not allow third-party interlocks that do not have a NRTL approval. Also note that any circuit breaker that is "back fed" MUST have a means of securing it in the panel other than just the cover plate.

In my opinion interlocks are a poor method for selecting the power source. First and foremost is that they do not switch the neutral conductor. Second is that they have greater potential of overloading the generator. My own living with a small generator used only during power outages has proven to me that MOST people do not need the "flexibility" of being able to energize each and every circuit (not all at once) in their homes. There is also the problem of knowing when the utility power has been restored, something that is easy if you can leave the main circuit breaker closed and a lamp on a non-generator-energized circuit in the on position.

Nor do I advocate making any changes internal to the generator. First, it will likely void any warranty and second, it removes an important safety feature if you ever use the generator in a portable mode. Merely not connecting the equipment grounding conductor in the interconnect cable where it connects to the premises wiring breaks the offending neutral-equipment ground just as effectively with only a slight decrease in overall safety.
 
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Old 11-09-13, 09:46 PM
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Thanks for your advice Furd.
 
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Old 11-09-13, 10:59 PM
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I have found that the only time you would need to break the bond in the generator is if that generator has a main GFI breaker and it trips due to the neutral and grounds be connected together.
 
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Old 11-10-13, 07:49 AM
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In most cases installing a transfer switch (of any kind) upstream of the main panel is a substantially more complicated task compared with installing it downstream and having it control a subpanel to which you moved all of the circuits to be eligible to receive generator power. The complication is that you need to coordinate with the power company to shut off your power during the project. You do not need to shut off power to the building in order to install a subpanel.

In the former case, the 3 pole transfer switch will not by itself correct the neutral-ground bonding in two places. In the latter case it will.
 
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