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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => AC Power and Grounding => Topic started by: Jamin Lynch on October 28, 2019, 01:10:20 pm

Title: Generator Bonding Question
Post by: Jamin Lynch on October 28, 2019, 01:10:20 pm
I recently helped out with an event where the sound company tied into the main lugs on a 25k gennie. There was a bonding bar between the neutral and ground. There was some question at the time whether to leave it or remove it.

What would be the proper procedure for that?

Thanks
Title: Re: Generator Bonding Question
Post by: Tim McCulloch on October 28, 2019, 02:05:44 pm
I recently helped out with an event where the sound company tied into the main lugs on a 25k gennie. There was a bonding bar between the neutral and ground. There was some question at the time whether to leave it or remove it.

What would be the proper procedure for that?

Thanks

Yes, presuming the generator's ground terminal was bonded to the genset trailer.  Code requires that neutral be bonded to the Grounding Electrode System *at the point of service* and a generator is considered the point of service (and it's also a "separately derived service" in Code-speak).  For generators there is the additional requirement (other than "cord and plug" connected to outlets on the generator itself) that the neutral be bonded to the generator frame, and the generator must be connected to a Grounding Electrode.

No other neutral/ground bonding should be used in the power distribution system.

Title: Re: Generator Bonding Question
Post by: Mike Sokol on October 29, 2019, 07:31:52 pm
Yes, presuming the generator's ground terminal was bonded to the genset trailer.  Code requires that neutral be bonded to the Grounding Electrode System *at the point of service* and a generator is considered the point of service (and it's also a "separately derived service" in Code-speak).  For generators there is the additional requirement (other than "cord and plug" connected to outlets on the generator itself) that the neutral be bonded to the generator frame, and the generator must be connected to a Grounding Electrode.

No other neutral/ground bonding should be used in the power distribution system.

Exactly right...
Title: Re: Generator Bonding Question
Post by: charles strickland on January 16, 2020, 05:05:17 pm
 Question , in the case of say a eu7000 honda were the neutral and  ground are not connected, should that be done at the coard set ?
Title: Re: Generator Bonding Question
Post by: Steve-White on January 16, 2020, 08:21:03 pm
Question , in the case of say a eu7000 honda were the neutral and  ground are not connected, should that be done at the coard set ?

No, per NEC is must be done at the source which in this case is the generator.  I don't remember the chapter and verse, it's been about 40 years ago.  When using a genset for backup power it's generally assumed the main service entrance panel has the neutral tied to ground and that's the only point - so sub panels, generators, equipment it floats.

When using a genny for event type power or stand-alone power, the neutral needs to be tied to ground and the generator is supposed to be grounded - not sure how often that happens.
Title: Re: Generator Bonding Question
Post by: charles strickland on January 16, 2020, 09:38:00 pm
Does this sound like crazy talk? I'm at a show in the park last weekend, aluminum stage sitting in the middle of a solid city block of concrete.the sound tec is setting up a generator feeder to a rack at the stage,I can't help myself and ask him how long will it take to drive in the ground stake. he said he wasn't using one that the ground and the neutral were floating. I've heard of a floating neutral but a floating ground. is there such a thing?
Title: Re: Generator Bonding Question
Post by: Steve-White on January 16, 2020, 11:17:42 pm
Does this sound like crazy talk? I'm at a show in the park last weekend, aluminum stage sitting in the middle of a solid city block of concrete.the sound tec is setting up a generator feeder to a rack at the stage,I can't help myself and ask him how long will it take to drive in the ground stake. he said he wasn't using one that the ground and the neutral were floating. I've heard of a floating neutral but a floating ground. is there such a thing?

The only thing floating was between his ears - clueless, BS'ing or both - I'd cast my vote in favor of clueless, with a bouquet of BS'ing to shake you off the trail.
Title: Re: Generator Bonding Question
Post by: Mike Monte on January 16, 2020, 11:52:48 pm
No, per NEC is must be done at the source which in this case is the generator.  I don't remember the chapter and verse, it's been about 40 years ago.  When using a genset for backup power it's generally assumed the main service entrance panel has the neutral tied to ground and that's the only point - so sub panels, generators, equipment it floats.

When using a genny for event type power or stand-alone power, the neutral needs to be tied to ground and the generator is supposed to be grounded - not sure how often that happens.

The first time I ever thought about grounding a portable generator was when I was playing in a band at an Octoberfest in NH...had to be 15+ years ago.  We were playing on a portable stage with a portable generator for band power.

I had nothing to do with the PA so I went about my business setting up.

The PA got up and running with seemingly no problems.
As set up continued one of the band members (Electrical Engineer by trade) took a look at the generator and began shaking his head...  He then went out to his truck and came back with a set of "auto battery jumper cables" and proceeded to clip one end of claws on the gen's frame and the other end's claws to one of the metal stakes (driven into the ground) that supported the tent. 

"It didn't look safe..." he said.
 
 
Title: Re: Generator Bonding Question
Post by: Rob Spence on January 18, 2020, 10:16:40 pm
I made up a plug as suggested by Mr. Sokol where I took an orange male cord cap, connected neutral to ground and then labeled it.

Just plug it in to a receptacle on the generator and instant bond.
Title: Re: Generator Bonding Question
Post by: charles strickland on January 18, 2020, 11:38:02 pm
  So could I then add a jumper from my N to G in the 30 amp twist for the genny side and have my CS 50 on the other end that goes to my distro ? I understand that limits my 50 amp distro to 30 amp but does that get me a bonded neutral to ground at the genny ?             
   ( Drive a grounding rod in and I'm good to go. )
Title: Re: Generator Bonding Question
Post by: Steve-White on January 19, 2020, 12:59:29 am
  So could I then add a jumper from my N to G in the 30 amp twist for the genny side and have my CS 50 on the other end that goes to my distro ? I understand that limits my 50 amp distro to 30 amp but does that get me a bonded neutral to ground at the genny ?             
   ( Drive a grounding rod in and I'm good to go. )

That would work.  However, probably not kosher per NEC.  The generator should have provisions built into the power panel to bond the neutral to chassis ground.  That would be proper.  I can’t advise on this, but wouldn’t do it.

Liability there and safety.  There should be a bus, which may just be a stud.

Maybe someone else knows and can better describe it.  Find out the “right” way to do do it and be sure.

What generator are you using?  Are you sure it isn’t already bonded?  “Backup” is the key - to use a generator as backup power for a building the neutral floats in the generator and gets tied to ground in the service entrance panel.

Whereas generators designed for stand alone power have the neutral tied to chassis ground inside the power panel.  The generators I have can be used either way by bonding or removing the neutral depending upon usage.  Yours may be one that can be used for either application.

Look at user manual, if not sure call tech support or find somebody that is qualified to assist you.
Title: Re: Generator Bonding Question
Post by: Tim McCulloch on January 19, 2020, 11:42:57 am
The common way to bond neutral with ground is with an Edison 15 amp male plug, with a 12ga shorting wire between the neutral and ground terminals.  Just plug it in to 1 of the 2 Edison outlets on the face of the portable generator.
Title: Re: Generator Bonding Question
Post by: Steve-White on January 19, 2020, 12:12:35 pm
The common way to bond neutral with ground is with an Edison 15 amp male plug, with a 12ga shorting wire between the neutral and ground terminals.  Just plug it in to 1 of the 2 Edison outlets on the face of the portable generator.

I like that, very simple.  Wasn't sure it that was legit or not per NEC.  Just make up a shorting or jumper plug right?
Title: Re: Generator Bonding Question
Post by: Tim McCulloch on January 19, 2020, 01:11:53 pm
I like that, very simple.  Wasn't sure it that was legit or not per NEC.  Just make up a shorting or jumper plug right?

Yep!

Mike Sokol had some comments here in this forum, IIRC, and he also posts about it in the recreational vehicle forums he participates in.
Title: Re: Generator Bonding Question
Post by: charles strickland on January 19, 2020, 03:15:12 pm
 But what if I'm using the 30 amp split twist lock plug ?  I haven't used this type genny before,  just curious how to safely use an inverter style genny. ( honda eu's )  I see it used for sound a lot, might I add with no ground rod. I just wondered how they were bonding it. The lack of a grounding rod suggest they probably weren't.
Title: Re: Generator Bonding Question
Post by: Tim McCulloch on January 19, 2020, 04:41:18 pm
But what if I'm using the 30 amp split twist lock plug ?  I haven't used this type genny before,  just curious how to safely use an inverter style genny. ( honda eu's )  I see it used for sound a lot, might I add with no ground rod. I just wondered how they were bonding it. The lack of a grounding rod suggest they probably weren't.

Ground and neutral are the same regardless of the outlet type.  What Code specifically prohibits is bonding neutral and ground *at the load or its cord* which is why your earlier suggestion is not acceptable.

Code also permits ungrounded generators to power "plug and cord connected loads directly from an outlet on the generator frame."  If you're powering a distro from this 30 amp outlet, you'll need to bond the generator frame to a 'grounding electrode system.'

Search terms:  "separately derived service" and "National Electrical Code 445"

Title: Re: Generator Bonding Question
Post by: charles strickland on January 19, 2020, 04:57:31 pm
 Thanks Rob.  I didn't quite understand what you meant. So I went to mikes web site N S Z found cool video on it. I was going to build one but then I thought I'll get one from mike only to find out no longer available and his looks a lot cooler than the one I'm going to build. Should come in handy someday down the road.  Better to have and not to need . Thanks again.
Title: Re: Generator Bonding Question
Post by: charles strickland on January 19, 2020, 05:01:00 pm
   Got it Mike,  Thanks.
Title: Re: Generator Bonding Question
Post by: charles strickland on January 19, 2020, 05:07:04 pm
   Good thing I don't drink.  I meant to say,  Got it and Thank you   Tim
Title: Re: Generator Bonding Question
Post by: Stephen Swaffer on January 20, 2020, 01:31:19 pm
Does this sound like crazy talk? I'm at a show in the park last weekend, aluminum stage sitting in the middle of a solid city block of concrete.the sound tec is setting up a generator feeder to a rack at the stage,I can't help myself and ask him how long will it take to drive in the ground stake. he said he wasn't using one that the ground and the neutral were floating. I've heard of a floating neutral but a floating ground. is there such a thing?

I've mentioned it before-but this scenario again begs the discussion of grounding versus bonding.  Grounding is required by the NEC-but so is bonding and, in this case with a big aluminum stage, critical.  Bonding is creating an intentional metallic connection between anything which is likely to become energized-and an aluminum stage with cabling on it certainly qualifies-all it would take is a pinched cord to energize the entire stage.

Recently at my day job one of my techs installed some control buttons on a metal pole anchored to the concrete floor.  He failed to bond correctly, he also pinched a wire against a screw holding the plastic box onto the pole.  This energized the pole resulting in complaints.  Ultimately the mistake is on me as the supervisor-but we corrected it before we had an injury and had some training regarding the importance of bonding! Properly bonded, this would have blown a fuse/breaker and we would have found the problem in a much safer manner.
Title: Re: Generator Bonding Question
Post by: Rob Spence on January 23, 2020, 05:58:08 pm
  So could I then add a jumper from my N to G in the 30 amp twist for the genny side and have my CS 50 on the other end that goes to my distro ? I understand that limits my 50 amp distro to 30 amp but does that get me a bonded neutral to ground at the genny ?             
   ( Drive a grounding rod in and I'm good to go. )

I would not do that. That produces an odd and not to code cable assembly.

Just make up the NEMA 5-15p I referred to above. Plug it in if you need the bonding.
Title: Re: Generator Bonding Question
Post by: charles strickland on January 24, 2020, 10:19:13 am
   Thanks Rob,  I made one and it looks almost as good as mikes. put it in my  box so i will have it when I need it. Thanks again. Charles
Title: Re: Generator Bonding Question
Post by: Mike Sokol on January 28, 2020, 07:00:11 am
Yep!

Mike Sokol had some comments here in this forum, IIRC, and he also posts about it in the recreational vehicle forums he participates in.

Yes, a simple "Edison" plug with the Neutral and Ground bonded together will effectively "bond" the floating neutral on most of these inverter generators. I developed this for  the RV industry first, then discovered that the Honda generators we were renting for small gigs had floating neutrals. The NEC allows this for powering a single appliance or tool without earth-grounding the generator, which is why contractors needing to run an electric saw can just throw and go. But once you start distributing power to multiple points (like a stage) then a neutral-ground bond is reuqired, along with an earthing grounding rod. You also need to bond any metal stage and stairs to this same neutral/ground bonding point. Now on larger generators there is typically an access panel and a place to install a shunt between the neutral and ground, but non of the small inverter generators have this option. That's why I developed the simple G/N bonding plug with you can purchase from Southwire on Amazon if you like, or just get a basic plug from a big box store and install a Ground-to-Neutral as indicated. https://tinyurl.com/s6e2o7t