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Floating vs Bonded Neutrals


Hi All - I am almost done my DJC rebuild - I am rebuilding the transfer pump now. I have my...

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Old 05-16-2005, 12:49 PM
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Default Floating vs Bonded Neutrals

Hi All - I am almost done my DJC rebuild - I am rebuilding the transfer pump now. I have my summary written, but the photos are on a different computer, and I have to have the story catch up with the text. I will post soon.

I have a question about floating neutral generators and it begins here.

I am presently renovating (yet another) room in the home - a room that contains the panel box. I will be adding a Siemens 12 circuit generator panel, a panel that transfers the neutral and is for use with "Neutral Bonded to Frame" generators, such as my DJC and Lincoln Ranger 8 welder.

However, I also have two Kawasaki portables (GA 1400 and GA 3200) that are labelled "Floating Neutral". After reading the requirements of the electrical codes, these generators are not intended to be used with the panel I am chosing. My question is: can these two small generators be converted (and relabelled) to be "Neutral Bonded to Frame" generators? Is it as simple as connecting the neutral to the ground terminal? More difficult? Impossible?

Your opinion and advice are appreciated.

John
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Old 05-16-2005, 03:42 PM
B.Sparks B.Sparks is offline
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Default Re: Floating vs Bonded Neutrals

I do not know the Canadian electrical codes, so my advice is worth what you are paying for it.

Converting your Kawasaki sets to bonded neutral is as simple as connecting the neutral to the frame. However, doing so introduces a safety concern. Assuming you a powering a 240 volt load or a PERFECTLY balanced 120 volt load, the neutral carries no current. That's seldom the case. In most instances there will be at least some imbalance between the 2, 120 'sides' resulting in current flow through the neutral. The resulting voltage drop in the neutral will cause a slight potential difference between the machine frame and "true" earth ground. Ordinarily this will, of course, be a very small voltage. But under certain condition (surges, motor starts etc.) the potential difference can possibly 'spike' to noticible levels.

Unless your electrical codes call for something else, I'd leave the neutral unboded on the Kawasaki sets, and run a seperate wire from the frame of the machine to a known, good earth ground. Or I'd use a 4 pole plug and 4 conductor wire (2 lines, neutral and grounding conductors.)
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Old 05-16-2005, 10:06 PM
Steve Dawkins Steve Dawkins is offline
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Default Re: Floating vs Bonded Neutrals

John,

Do your Kawasaki portables have GFCI protection? If so, this may explain why the neutrals are floating. Normally, portable gensets have the neutral bonded to the frame. This is fine as long as the unit is being used strictly as a portable generator to supply cord connected loads such as power tools, appliances, lights, etc. When these same portables are connected to an electrical service panel, problems can arise. The National Electrical Code requires that services have the neutrals and grounds bonded together. When a portable generator is connected to a service that is bonded, the GFCI on the generator trips. This will happen as soon as the generator is started or connected to the service. It appears there is a short or ground fault condition causing this problem. In reality, the ground fault sensor is tripping because the generator is neutral bonded and the service is also neutral bonded. (If a GFCI device "sees" a neutral/ground connection downstream of the GFCI, it trips.) We've had this condition happen many times with Honda portable gensets that were wired as home standby units. Honda put out a service bulletin showing how to disconnect the bonding jumper in the end bell of the generator. They also supplied a label to install on the generator to notify personnel that the generator was no longer neutral bonded.

I'm curious about your 12 circuit Siemens panel. I have a similar panel in my house that I installed as the emergency power panel. It has two interlocked two pole circuit breakers that serve as a manual transfer switch. Both of these breakers are plugged onto a common bus that feeds the twelve branch circuit breakers. The neutral is considered a solid neutral, as it is not switched with the "hot" conductors. Does your panel actually switch the neutrals?

The National Electrical Code treats generators differently depending on whether the neutrals for utility power and generator power are switched or tied (bonded) together. When the neutral is switched, the generator is classified as a separately derived service, and requires different grounding techniques. Most of the standby generators we install do not switch the neutrals, and the neutral floats at the generator. The only place that the neutral and grounds are bonded is the service panel.

Good luck with your DJC project. Been there, done that!

Steve
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Old 11-29-2005, 11:49 PM
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Default Re: Floating vs Bonded Neutrals

I am dredging this post back up again as I am still not 100% sure about converting my two Kawasaki portables from floating neutral to neutral bonded. I understand and appreciate the replies, but I'm still not sure. I want to be able to use them both as stand-alone units for power tools, as well as be able to hook them to to the house for short outages rather than haul around the 1,400 lb DJC/trailer or crane the welder into the truck.

My DJC and Lincoln Ranger 8 are both neutral bonded, and that is how I configured my transfer switch. I installed my Siemens EQG660D transfer panel. It is a 12-circuit, 60-amp 3-pole panel that will, as I configured it, transfer two hots as well as the neutral - as required for a neutral-bonded-to-frame generator. (The panel also has the option of being configured for use with a floating-neutral generator in which only two of the three poles would effectively be used (transferring the hots) - the neutral would be bonded to the service and not transferred).

In the DJC, neutral bonding is done as simply as lugging the neutrals to the output box frame, where the ground wire is also connected. Do I understand that both the theory and practice of bonding these two small Kawasakis is that straight forward? That would allow the neutral to meet code on these little genertors by only being grounded in one spot: from the generator back through the generator-connection cord, through the transfer panel ground that is hooked to the main panel ground that is hooked to my incoming copper water line.

Will they still operate as stand-alone (corded tools) generators when the neutral is bonded? I have set the DJC up with receptacles on the output panel, and the Lincoln came with them, so I don't see there being a probelm, but, hey, I'm a forester and just a hobby electrician, and you are the practicing professionals. I'd appreciate your further thoughts.

John
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Old 11-29-2005, 11:51 PM
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Default Re: Floating vs Bonded Neutrals

I forgot to add - the Kawasaki GA 1400 and GA 3200 are not GFCI-equipped and neither are the DJC nor Lincoln.
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