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Author Topic: Portable Generator Neutral Bonding  (Read 630 times)

jasonfinnigan

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Re: Portable Generator Neutral Bonding
« Reply #10 on: June 29, 2014, 06:44:54 pm »

BTW: I'm going to try my bed-o-nails "Sokol Ground" later this week. My plan is to install it in the corner of my yard and run a fall of potential test under various wet and dry conditions. That way I can see if it's a viable solution at all and gather some empirical data as to its actual ground impedance. If by chance it comes in under 100 ohms under standard soil conditions, I'm going to petition the NEC committee for a variance to allow it for portable generator use. We shall see if it works or I'm barking up the wrong tree.

That would be great if it was. people driving ground rods never really check for underground wires, they just do it. How do they know they won't hit anything, Does code require underground wires to be lower? I thoguht NEC requirement was only 18inches underground. Just curious incase we ever start doing this in house instead of having the Genny rental company take care of it.
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Mike Sokol

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Re: Portable Generator Neutral Bonding
« Reply #11 on: June 30, 2014, 07:28:36 am »

One more thing to know is that there's a class of really cheap Chinese inverter generators that have a 60-60 volt balanced output. That is, they measure 60 volts from hot to frame/ground and 60 volts from neutral to frame/ground with a low impedance connection. Of course, you can't neutral-bond these generators, nor can you use them to power your house in the event of an extended power outage. That's because you'll short out the neutral and trip the genny overload circuit. If these are properly earth grounded they should be safe for outside stage use. However, they tend to have very dirty power and make sound systems buzz (lots of harmonics in the AC waveform) so I don't think they're an option for sound system power except during zombie apocalypse situations.  ;D

Steve M Smith

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Re: Portable Generator Neutral Bonding
« Reply #12 on: June 30, 2014, 08:09:45 am »

that have a 60-60 volt balanced output. That is, they measure 60 volts from hot to frame/ground and 60 volts from neutral to frame/ground

I like the idea of a centre tapped ground.  In the UK, building site tools are powered via 110 volt isolation transformers with a centre tapped ground.


Steve.
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frank kayser

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Re: Portable Generator Neutral Bonding
« Reply #13 on: June 30, 2014, 11:27:51 am »

In my quest for additional information on grounding, I found an on-point article that largely supports the principles Mike has set out.


http://www.lightingandsoundamerica.com/mailing/plasaprotocol/pspring12_shadowandlight.pdf


The only "discrepancy" is the following statement, which the writer does not directly address except in context of premises wiring.



"A common misconception about setting up power distribution
for portable stages is to install a bonding jumper between the
grounded conductor (neutral) and the grounding conductor
(equipment ground or grounding electrode conductor)."


The writer goes on to say:



"In a building, there is one, and only one, main bonding jumper that
bonds the neutral and the grounding system to insure that a ground
fault will find a low-impedance path back to the source, but, in a
separately derived system like a portable power generator, the system
bonding jumper is typically in the portable power generator.
the purpose of the bonding jumper is to earth the electrical
system in order to provide a good 0 V reference (voltage is
meaningless without a reference), to limit voltage surges due to
lightning, line surges, or unintentional contact with higher voltage
lines, and to provide a low-impedance path for fault current that
will insure that the fuse or circuit breaker will open in the event
of a ground fault. if a second bonding jumper is installed in a

distribution panel, it creates a parallel path for normal return
current through the neutral and the grounding conductor. that is
what is known as “objectionable current.”"


I do not find this at odds with what Mike Sokol has to say with bonding the neutral with ground at the generator.


I anxiously await Mike's further testing/ruling on his "bed of nails" portable earthing solution.


frank
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Don Davis

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Re: Portable Generator Neutral Bonding
« Reply #14 on: June 30, 2014, 06:21:43 pm »

I just found a really good list of hundreds of portable generators which shows if they have bonded or floated neutrals. http://www.generlink.com/CompatibleGenerator.pdf

In summary: If a portable generator already has a bonded neutral, then the only thing you need to do for outdoor stage use is drive a ground rod and attach it to the generator's ground lug. However, a generator with a floated neutral should also be G-N bonded to provide a direct fault path back to the power source in the event of a Line-to-Chassis short in a piece of stage gear. In addition to that, any metal stage structure should also be bonded to the generator's earth grounding point to prevent differential voltages between stage metal and an amplifier chassis which would cause a shock hazard to musicians and stage technicians.

I think the above statement is pretty logical. However, if any of you feel it should be edited for clarity or content, please add to the discussion.

Thank you Mike and all the guys who contribute to this forum, I'm learning tons about using portable power more safely. FYI, I'm a sound guy, not an electrician.

I recently purchased a used Honda EX5500 for use with our portable PA system. Using the list provided in this thread it appears that it has a floating neutral. We definitely fall into the category of powering multiple devices from this generator, for instance we will power an amp rack, FOH mixer and stage power as typical. So this discussion is real world for me. So, should we bond the G-N within the genny?

I have read the owner's manual from Honda and grounding is only briefly mentioned and nothing is said about bonding or how that would be accomplished. There is a ground lug provided for earth grounding. I'm not asking for specifics on how to bond them due to liability issues and so forth but is it the consensus they should be bonded and should it be done in a way that it can be left that way? Any suggestions you guys have that will help us use this equipment in as safe a manner as possible is greatly appreciated.

Also, I will have a pro do the work if its the right thing to do.
Just an aside, why would they sell floating neutral generators in the first place?
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jasonfinnigan

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Re: Portable Generator Neutral Bonding
« Reply #15 on: June 30, 2014, 06:44:49 pm »

Also, I will have a pro do the work if its the right thing to do.
Just an aside, why would they sell floating neutral generators in the first place?

It has to do with how they are used. one reason is a lot of people using the smaller generators aren't even using grounding rods as they should so ground isn't ground.  Secondly when using a transfer switch for a house the grounded conductor (Netrual) is generally not switched.

Yes, you should be bonding it, you could make a cord to plug into and outlet on the generator that only has the neutral connected (Make sure it's grounded and polarized) and connect that down to the grounding lug - and then to your grounding rod, I would not modify the inside of the generator if it was me. I'm sure mike might have other suggestions on this.
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Frank DeWitt

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Re: Portable Generator Neutral Bonding
« Reply #16 on: June 30, 2014, 06:52:07 pm »

The easy way to ground the neutral to the frame is to use one of Mike's tricks.  Make a plug with a wire between ground and neutral.  You have 5 outlets on there so just pick one, get a matching plug and put the jumper on it.

From Mike's web site
http://www.noshockzone.org/generator-ground-neutral-bonding/

One reason the neutral is not bonded is for use with a building that has a transfer switch such as a backup for a home.  In that case the building wiring provides the ground and the feed to the transfer switch provides a ground to the generator from the house.   (As a rule, you want no more then one and no less then one tie between neutral and ground.)
« Last Edit: June 30, 2014, 07:20:55 pm by Frank DeWitt »
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Mike Sokol

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Re: Portable Generator Neutral Bonding
« Reply #17 on: June 30, 2014, 07:28:38 pm »

The easy way to ground the neutral to the frame is to use one of Mike's tricks.  Make a plug with a wire between ground and neutral.  You have 5 outlets on there so just pick one, get a matching plug and put the jumper on it.

From mics web site
http://www.noshockzone.org/generator-ground-neutral-bonding/

One reason the neutral is not bonded is for use with a building that has a transfer switch such as a backup for a home.  In that case the building wiring provides the ground and the feed to the transfer switch provides a ground to the generator from the house.   (As a rule, you want no more then one and no less then one tie between neutral and ground.)

That's correct. I generally just take a 15-amp Edison plug and put a jumper between the Neutral (white screw) and Ground (green screw). Then be sure to mark this as "G-N Bond - Generator" so it doesn't get mixed up or lost. You only need one of these plugged into any available receptacle/outlet on the generator to G-N bond the entire system. Then if you need to float the neutral because you're powering your house service panel, just pull out the plug and you're in business.

Be aware if you're doing this on parallel Honda generators that their banana plug jumpers aren't color coded. So you should install this G-N bond in the "companion" generator or the external combiner box. If not, you could create a revere polarity outlet. Not terribly dangerous like an RPBG (Reverse Polarity Bootleg Ground) but not up to code, either. If I had a parallel generator set I would simply mark the jumper wires for the neutral and hot connections and never worry about it. But a quick check after installing my G-N jumper plug is to use a 3-light outlet tester everyone seems to carry with them. 
« Last Edit: June 30, 2014, 07:40:28 pm by Mike Sokol »
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Stephen Swaffer

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Re: Portable Generator Neutral Bonding
« Reply #18 on: July 01, 2014, 12:48:24 am »


in a separately derived system like a portable power generator, the system
bonding jumper is typically in the portable power generator.


In reading my local POCO service manual the other day in the process of designing a transfer switch setup, they used theses terms:

separately derived system=generator with the neutral and ground bonded.  This setup is designed to be used stand alone to power equipment.

non-separately derived system=generator without a neutral - ground bond.  This setup is NOT to be used stand alone, but rather designed to supply a system-such as in a building-that already has a neutral-ground bond.

If you are using a "separately derived system" neutral-ground bonded genny on a building as a backup genny you are supposed to use a transfer switch that switches the neutral.

Obviously, adding a bonding jumper converts a non-separately derived system into a separately derived system-which then can be used to power your gear.

Not trying to confuse anyone-but  you might come across this terminology in a manual.
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Steve Swaffer

Mike Sokol

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Re: Portable Generator Neutral Bonding
« Reply #19 on: July 01, 2014, 06:40:54 am »

In reading my local POCO service manual the other day in the process of designing a transfer switch setup, they used theses terms:

separately derived system=generator with the neutral and ground bonded.  This setup is designed to be used stand alone to power equipment.

non-separately derived system=generator without a neutral - ground bond.  This setup is NOT to be used stand alone, but rather designed to supply a system-such as in a building-that already has a neutral-ground bond.

If you are using a "separately derived system" neutral-ground bonded genny on a building as a backup genny you are supposed to use a transfer switch that switches the neutral.

Obviously, adding a bonding jumper converts a non-separately derived system into a separately derived system-which then can be used to power your gear.

Not trying to confuse anyone-but  you might come across this terminology in a manual.

This all is standard "code speak". And as far as I can determine after discussing with few POCO guys, Honda tech support, and an engineer who used to design substations, an Edison G-N bonding plug in a small portable generator is a valid G-N bonding method. Of course, if your generator has camlocks, then you should bond with a camlock jumper or full ampacity transfer switch.
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