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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: Stephen Swaffer on August 31, 2014, 12:11:52 pm

Title: Bonding and false positive tests on GFCI
Post by: Stephen Swaffer on August 31, 2014, 12:11:52 pm
Since we were headed OT and somewhat irrelevant to the OPs post, I started a new thread, but I want to comment on Guy's staement.

"The false positive generated by GFCI test circuits on ungrounded Floating Neutral generators does nothing to eliminate faulty equipment and only creates a false sense of security."

First, it has been discussed in depth on other threads here that just because a generator is built without a bonded neutral/ground does not make it OK to use it like that if code does not allow it for the purpose.  The places that an unbonded neutral is allowed are limited-and there are ways to bond the neutral.

Secondly, I understand the argument behind your statement; however, what is the purpose for a GFCI?  Simply to prevent electrocuting someone.  If I place myself between a hot and a neutral no GFCI will ever trip period.  If I place myself between a hot and ground-but there is no path back to the neutral (a VERY iffy proposition) then I will not be harmed -GFCI in circuit or not.  However, IF there is enough of a path (inadvertent or intentional) to allow a harmful 5 mA to travel through my body and return to the circuit bypassing the GFCI then a GFCI will in fact protect me with or with out a neutral "bond".

The correct way is to follow code and if you are using a genny to supply audio gear for a gig, make sure you bond the neutral and ground. And make sure that neutrals and grounds are separated in any distros/gear that you use.
Title: Re: Bonding and false positive tests on GFCI
Post by: frank kayser on August 31, 2014, 01:10:58 pm
Since we were headed OT and somewhat irrelevant to the OPs post, I started a new thread, but I want to comment on Guy's staement.

"The false positive generated by GFCI test circuits on ungrounded Floating Neutral generators does nothing to eliminate faulty equipment and only creates a false sense of security."

First, it has been discussed in depth on other threads here that just because a generator is built without a bonded neutral/ground does not make it OK to use it like that if code does not allow it for the purpose.  The places that an unbonded neutral is allowed are limited-and there are ways to bond the neutral.

Secondly, I understand the argument behind your statement; however, what is the purpose for a GFCI?  Simply to prevent electrocuting someone.  If I place myself between a hot and a neutral no GFCI will ever trip period.  If I place myself between a hot and ground-but there is no path back to the neutral (a VERY iffy proposition) then I will not be harmed -GFCI in circuit or not.  However, IF there is enough of a path (inadvertent or intentional) to allow a harmful 5 mA to travel through my body and return to the circuit bypassing the GFCI then a GFCI will in fact protect me with or with out a neutral "bond".

The correct way is to follow code and if you are using a genny to supply audio gear for a gig, make sure you bond the neutral and ground. And make sure that neutrals and grounds are separated in any distros/gear that you use.
The problem I see is that generators are sold consumer-off-the-shelf (COTS) to end users that have no idea about code or situations where they should or should not be used.  I know my Honda EU1000 specifically states not to drive a ground rod and has no mention of whether it is a floating or bonded ground.  In ways, it seems that including too much information may be seen as the manufacturer as an additional point of liability.  The "plug it in, and if you don't understand that, get an electrician" mindset works for and against them.
I don't think Honda had it in mind that their EU gennies would be powering audio rigs - though their use seem a natural to us.  Honda does have their EB series gennies with GFCI and bonded ground, which probably would be more suitable... 

Title: Re: Bonding and false positive tests on GFCI
Post by: Stephen Swaffer on August 31, 2014, 06:14:10 pm
The "plug it in, and if you don't understand that, get an electrician" mindset works for and against them. 

Arguably a reasonable position to take for the average consumer.  I don't consider sound/lighting providers the "average consumer."  When you provide a service to the public, you are take on responsibility for "the public's" safety.

As an electrician, there are a dozen or more trades-from operating heavy equipment, to welding, structural design, rigging, etc. that I need to know the basics of and be able to handle simple things as well as know when to call an expert.  IMO grounding is a basic safety consideration that anyone setting up sound gigs with either shore or genny power needs to thoroughly understand ( this forum is an excellent tool to accomplish that) so they can get it right-or know they need to call an expert "this" time.

Grounding is not as sexy or fun as setting up a bunch of gee whiz effects processors, amps, subs etc but it is just as necessary as driving to the gig.
Title: Re: Bonding and false positive tests on GFCI
Post by: Jeff Bankston on August 31, 2014, 07:09:45 pm
in los angeles any generator thats built on a set of wheels has to be connected to a ground rod. even all of our contruction site gens had to have a permit from la building and safety and a ground rod driven at the gen. the electrical inspector would come and inspect before we were allowed to use it. a friend runs gens for tv/movie shoots , i will ask him what is required for his 18 wheeler gen rig.
Title: Re: Bonding and false positive tests on GFCI
Post by: Mike Sokol on August 31, 2014, 09:36:27 pm
in los angeles any generator thats built on a set of wheels has to be connected to a ground rod.

And I'm guessing the generator must also have its neutral bonded to this "earth ground". Any requirements for metal stages to be bonded to this same generator "ground"? 
Title: Re: Bonding and false positive tests on GFCI
Post by: Jeff Bankston on September 01, 2014, 03:53:49 am
And I'm guessing the generator must also have its neutral bonded to this "earth ground". Any requirements for metal stages to be bonded to this same generator "ground"?
i bond steel frame of the wood deck trailer to the disto panel ground which is connected to the generator ground. metal steps are bonded to the trailer.
Title: Re: Bonding and false positive tests on GFCI
Post by: Guy Holt on September 01, 2014, 08:03:20 pm
... a friend runs gens for tv/movie shoots , i will ask him what is required for his 18 wheeler gen rig.

Unless something changed very recently, it was my understanding from my West Coast IA brothers that the preferred practice in Los Angeles was to not earth ground generators, but rather completely insulate them from earth as stipulated in this excerpt of the safety guidelines established by the Safety Committee of the Contract Service Administration Trust Fund (CSATF), an industry wide administrative body (governed by the collective bargaining agreement by and between the Producers, The International Alliance of Theatrical Stage Employees ("I.A.T.S.E."), the Moving Picture Technicians Artists and Allied Crafts of the United States, its Territories, and Canada ("M.P.T.A.A.C."); as well as the collective bargaining agreements by and between the Producers and the Basic Crafts Locals (Article 18))..

“Generators mounted on trucks or trailers shall be completely insulated from earth by means of rubber tires, rubber mats around metal stairways and rubber mats under any type of lift gate or jacking device. Metal supports for trailers shall be insulated by means of wooden blocks. Safety tow chains shall be secured so as to not touch the ground. If complete insulation is not possible, a grounding electrode system shall be installed per the National Electrical Code, Article 250.52.”

Guy Holt, New England Studio Mechanics/IATSE Local 481 Certified Gaffer
ScreenLight & Grip
rentals@screenlightandgrip.com
Title: Re: Bonding and false positive tests on GFCI
Post by: Stephen Swaffer on September 02, 2014, 01:13:25 am
I question the wisdom of this preferred method.

First, it would seem to require at least as much effort as providing a good earth ground.

Second, all the careful isolation can be undone with just one careless placement of any metallic tool, stand what have you or even somebody leaning against the trailer .  Maybe in a tightly controlled studio lot (though I am not usually that trusting of coworkers when it comes to my safety)-but very iffy in a venue with public access.

Though LA is probably a drier environment than I am used to so perhaps less susceptible to accidental grounds and harder to get a good ground?
Title: Re: Bonding and false positive tests on GFCI
Post by: Jonathan Johnson on September 02, 2014, 01:18:44 am
OK, this doesn't make sense to me.

If a generator has a floating neutral (not bonded to ground/frame of genny), then what's the point of a GFI that's factory-installed in the generator? A short to ground will never result in a complete circuit back to neutral upstream of the GFI, so it will never trip. In order for it to trip in the event of a downstream fault, there would have to be a fault WITHIN the generator itself, that creates an unintentional upstream bond between the generator circuitry and the frame.

What am I misunderstanding here? The whole idea of the GFI is that it detects current bypassing the GFI. And if there is no bond upstream, there can be no current bypassing the GFI.
Title: Re: Bonding and false positive tests on GFCI
Post by: Jeff Bankston on September 02, 2014, 01:31:32 am
Unless something changed very recently, it was my understanding from my West Coast IA brothers that the preferred practice in Los Angeles was to not earth ground generators, but rather completely insulate them from earth as stipulated in this excerpt of the safety guidelines established by the Safety Committee of the Contract Service Administration Trust Fund (CSATF), an industry wide administrative body (governed by the collective bargaining agreement by and between the Producers, The International Alliance of Theatrical Stage Employees ("I.A.T.S.E."), the Moving Picture Technicians Artists and Allied Crafts of the United States, its Territories, and Canada ("M.P.T.A.A.C."); as well as the collective bargaining agreements by and between the Producers and the Basic Crafts Locals (Article 18))..

“Generators mounted on trucks or trailers shall be completely insulated from earth by means of rubber tires, rubber mats around metal stairways and rubber mats under any type of lift gate or jacking device. Metal supports for trailers shall be insulated by means of wooden blocks. Safety tow chains shall be secured so as to not touch the ground. If complete insulation is not possible, a grounding electrode system shall be installed per the National Electrical Code, Article 250.52.”

Guy Holt, New England Studio Mechanics/IATSE Local 481 Certified Gaffer
ScreenLight & Grip
rentals@screenlightandgrip.com
i dont know what the motion picture/la la palooza type events/tv shows do about grounding but when i or anyone else goes to rent a gen on axles we "must" have a gen pernit from the city of los angles. if we dont have a permit we are not allowed to rent a gen. once we have the permit the rental company delivers the gen. an electrical inspector comes before the event to make sure an 8' ground rod is driven next to the gen and a proper size ground wire is attatched. he also makes sure the gen isnt parked ubder a tree as i have ben told happens. if the stage is metal or has metal parts he checks that for grounding wires. after he signs off then and only then can i turn the gen on and power stuff up. the city of los angeles might have different rules for union crews but we are just a band doing our own stuff with my pa. we only play in daylight so no lights are used. i havent ben able to talk to my union friend that runs the big stuff cause he is on a production set working 12hr days right now.

also a friend bought 3 new MQ axle mounted gens about 18 months ago. we started using his 80KW gen and he wont let me hook my truck to it if i dont have a permit.
Title: Re: Bonding and false positive tests on GFCI
Post by: Jeff Bankston on September 02, 2014, 01:39:57 am
I question the wisdom of this preferred method.

First, it would seem to require at least as much effort as providing a good earth ground.

Second, all the careful isolation can be undone with just one careless placement of any metallic tool, stand what have you or even somebody leaning against the trailer .  Maybe in a tightly controlled studio lot (though I am not usually that trusting of coworkers when it comes to my safety)-but very iffy in a venue with public access.

Though LA is probably a drier environment than I am used to so perhaps less susceptible to accidental grounds and harder to get a good ground?
la isnt hard to ground and driving a ground rod is a piece of cake. the exception are if your not near a dirt patch but we never encountered any problems. when a club didnt have the power we needed we used a gen and i clamped the ground wire to the buildings cold water pipe and the inspector approved it.
Title: Re: Bonding and false positive tests on GFCI
Post by: Stephen Swaffer on September 02, 2014, 01:41:27 am
....there would have to be a fault WITHIN the generator itself, that creates an unintentional upstream bond between the generator circuitry and the frame.

A very high percentage of motors I replace have developed a short between the windings and the frame-and most motors have a measurable conductance to ground-especially with a little age.  I would expect the same of a genny-sooner or maybe a lot later there will be a connection like it or not.
Title: Re: Bonding and false positive tests on GFCI
Post by: Jonathan Johnson on September 02, 2014, 11:55:40 am
A very high percentage of motors I replace have developed a short between the windings and the frame-and most motors have a measurable conductance to ground-especially with a little age.  I would expect the same of a genny-sooner or maybe a lot later there will be a connection like it or not.

So then the GFI is there not to protect personnel, but to protect personnel in the event of a failure in the generator. I'm sure the advertising execs at Honda will be all over that one.  ;)
Title: Re: Bonding and false positive tests on GFCI
Post by: Tim McCulloch on September 02, 2014, 12:47:40 pm
So then the GFI is there... to protect personnel in the event of a failure in the generator.

That's a bad thing?  Not a "feature" the marketing dept will be pushing, but if it provides protection to the user in the event of insulation breakdown or convertor failure I'll be happy the GFI opens.
Title: Re: Bonding and false positive tests on GFCI
Post by: Rob Spence on September 02, 2014, 01:33:56 pm
I would imagine that the movie business sets up often enough in locations that would be difficult to drive a ground rod. Concrete streets? Bridges?


Sent from my iPad using Tapatalk HD
Title: Re: Bonding and false positive tests on GFCI
Post by: Guy Holt on September 02, 2014, 07:08:48 pm
OK, this doesn't make sense to me. If a generator has a floating neutral (not bonded to ground/frame of genny), then what's the point of a GFI that's factory-installed in the generator?

Almost all portable generators with factory installed master GFCIs have bonded neutrals – you are not missing something. It is the EU Series generators with floating neutrals that do not have GFCIs

The correct way is to follow code….

It is the latest revisions in code that don’t make sense to me. The 2014 edition of the NEC revised the language for section 445.20: Ground-Fault Circuit Interrupter Protection for Receptacles on 15 kW or Smaller Portable Generators as follows:

“All 125-volt, single-phase, 15-and 20-ampere receptacle outlets that are a part of a 15-kW or smaller portable generator either shall have ground-fault circuit-interrupter protection for personnel integral to the generator or receptacle or shall not be available for use when the 125/250-volt locking-type receptacle is in use. If the generator was manufactured or remanufactured prior to January 1, 2015, listed cord sets or devices incorporating listed ground-fault circuit-interrupter protection for personnel identified for portable use shall be permitted. If the generator does not have a 125/250-volt locking-type receptacle, this requirement shall not apply.”

What this means is that, as municipalities adopt the 2014 edition of the NEC, GFCI devices will have to be used on the 125V outlets of generators like the Honda EU6500is, or the new EU7000is, when a spider box or a large HMI light is used on the 240-volt twist-lock receptacle.

While this requirement makes perfect sense when the generator’s 240-volt twist-lock receptacle is being used for home stand by power via a 240V transfer switch, it makes no sense when it is being used to power a large HMI light on set. The reason the revised language of NEC 445.20 makes sense when a generator is used for home stand by power is because neutral and ground are bonded in the service panel of the house. Given this bond, cord set GFCIs plugged into the 125V outlets of the generator will operate reliably because there exists a ground fault circuit for fault current to go to, thereby creating an imbalance in the CT of the GFCI and causing it to trip. However, a large HMI light or spider box plugged into the generator’s 240-volt twist-lock receptacle does not bond neutral and ground, and so cord set GFCIs will not operate reliably because in this situation there is no ground fault circuit for fault current to go to. Regardless of what the NEC says, simply using a GFCI on an ungrounded Floating Neutral generator will not ensure a safe system, and can in fact be misleading because as state previously their test circuits generate a false positive.

Use these links  for more details on the latest code revisions as they pertain to portable generators:

https://soundforums.net/threads/8248-NFPA-decision-on-new-section-NEC-445-20-for-small-(-lt-15kW)-portable-generators

http://www.screenlightandgrip.com/html/emailnewsletter_generators.html#anchorElectrical Hazard Protection

Guy Holt, Gaffer
ScreenLight & Grip
rentals@screenlightandgrip.com
Title: Re: Bonding and false positive tests on GFCI
Post by: Stephen Swaffer on September 02, 2014, 08:17:10 pm
Guy, with all due respect you are missing the point of my OP.  The ONLY way someone gets eectrocutes is id current flows through their body, period.  If it returns to the genny via the neutral, the GFCI will never protect them-bonded neutral or not.  IF it finds any other path, the GFCI will trip.  How is this not safer?

I'll to double check, I am on the road with no access to my code book.  IIRC, chapter 250 which always applies unless there is an exception requires "separately derived" systems to have a bonded neutral.  A spider box plugged into the twistlock would qualify as a separately derived system and require a bonded neutral.  You can't factory build a spiderbox that way because, if is plugged into shore power it can not have a bonded neutral. At some point, the end user has to take responsibility for making sure the neutral is bonded when the NEC requires it.  Almost every breaker panel I buy has an unbonded neutral as shipped from the factory-but that doesn't mean I can use it that way.
Title: Re: Bonding and false positive tests on GFCI
Post by: Guy Holt on September 03, 2014, 08:54:54 am
Guy, with all due respect you are missing the point of my OP.  The ONLY way someone gets electrocuted is if current flows through their body, period.  If it returns to the genny via the neutral, the GFCI will never protect them-bonded neutral or not.  IF it finds any other path, the GFCI will trip.  How is this not safer?

Stephen, I get your point.  My point is that the false positive generated by GFCI test circuits on generators with floating neutrals, and the revised language of NEC 445.20, mislead the average user into thinking they are using a completely safe system when they are in fact not. Yes, a GFCI on an unbounded generator is safer than no GFCI at all, but a GFCI on a bounded generator that is earth grounded is safer still.

(http://www.screenlightandgrip.com/images/generators/481_GFCI_Wkshp_Demo_Set_Up_Sm.jpg)
(In an IATSE workshop I create a double fault situation with a fault in the Hot and Neutral conductors)

Take your example that a GFCI will never protect against a Hot to Neutral fault regardless whether the neutral is bonded or not. In an IATSE Local 481 training workshop I offer on Ground Fault Protection, I demonstrate just that. In the demonstration we create a double fault - one in the Hot, and a second in the Neutral.

(http://www.screenlightandgrip.com/images/generators/481_GFCI_Wkshp_Gen_SetUp3.jpg)
(Using a variable resistor, we leak current to ground and find that the GFCI does not trip)

We then use a variable resistor to leak current to ground and find that the GFCI does not trip because the fault current returns to the system via the neutral fault before passing through the CT of the GFCI.  As you rightly point out, this is a potentially hazardous situation. If an individual comes into contact with this ground fault circuit created by the two faults, fault current will travel through the individual on its' way back to the generator's windings without the GFCI ever registering a fault.

(http://www.screenlightandgrip.com/images/generators/SB_Test_Bonded_Full_Grd.jpg)

In a second demonstration illustrated above, we take the same double fault situation, but now bond the neutral and earth ground the generator. The GFCI trips every time. It trips because the ground rod and neutral bond creates a definite Ground Fault Circuit that splits the leakage current - making it impossible for balance to be restored to the system by all of the Fault Current returning to the Neutral through the second Fault before passing back through the GFCI. In other words, by diverting some of the Fault Current around the second fault, the ground rod assures that there will be an imbalance in the current traveling through the GFCI on the return side that will make the GFCI trip. Increasing the effectiveness of GFCIs in double fault situations is a compelling argument I think for, not being lulled into complacency by the false positive of GFCI test circuits, but instead bond and earth ground generators.  For the full content of my IA Ground Fault Protection Workshop, use this link: http://www.screenlightandgrip.com/html/481_GFCI_Workshop.html

A spider box plugged into the twistlock would qualify as a separately derived system and require a bonded neutral.

I don’t see how a spider box plugged into the twist-lock of a generator qualifies as a separately derived system. A separately derived system is a new impedance point where a new voltage is created. A spider box plugged into the twist-lock of a generator is at the same potential as the generator and is therefore a sub panel of the generator system and so should not be bonded.

Guy Holt, Gaffer
ScreenLight & Grip
rentals@screenlightandgrip.com
Title: Re: Bonding and false positive tests on GFCI
Post by: Mike Sokol on September 03, 2014, 11:25:52 am
Almost all portable generators with factory installed master GFCIs have bonded neutrals – you are not missing something. It is the EU Series generators with floating neutrals that do not have GFCIs

IIRC there is a UL exception that allow generators under 5KW to NOT have a GFCI if their neutral is floating. But generators with a bonded neutral and 120-volt outlets ARE required to have GFCI protection on the 20-amp outlet(s). However, there are no UL requirements for GFCI protection on 240-volt and higher amperage twist-lock outlets. UL documentation is a little harder to find than the NEC docs since it's specific to each industry, but anyone who builds an electrical device the USA is certainly aware of what it takes to get their products "UL Listed". I'll see if I can find the actual UL docs on this.

The key concept is that a single portable generator powering a single tool or movie light is likely safer if it's both neutral isolated and earth-ground floating. However, once you start distributing power to multiple drop points, such as a stage back-line and a FOH mixing console, you can see how something as simple as a pinched extension cord on stage or a musician plugging in a mis-wired stage amplifier could bias the grounding system to 120-volts above earth potential. So now your mixing guy at the FOH position could be electrocuted if he's standing on the wet grass and touches his gear rack or console.

And while I think that GFCIs are great and should be used for all back-line gear outlets, I don't know of any FOH engineers who would power their mixing console from one. The chance of a stray current leakage taking down an entire show is too much. Same for power amps powered by a twist-lock and a rack-pak. I don't know anyone who put's GFCIs on those circuits since I consider them to be "permanently installed".

I do know that other countries allow 30-mA Industrial GFCIs for power protection since the USA 6 mA threshold has too many trips under normal operation. But I don't think they would pass any inspection here, or am I missing something. 

My take on all this is that for distributed power for pro-stage situations we really want the generator to have a bonded neutral, a properly driven ground rod or bond to building steel, and all metal stage components to be bonded to the same power distro G-N-E connection point. Then there should be GFCI protected outlets for all stage power to offer shock protection to the musicians. If all that is properly implemented then it should be impossible for anyone on stage to suffer a life-threatening shock. Any shock at that point could be from an improperly wired/grounded guitar amp, and the best/easiest way to find that is to point your trusty NCVT (VoltAlert) at every stage amp as it's plugged in a turned on. While Guy may have complete control over his wiring distribution and what lighting gear is plugged into it, in the pro-sound world there's a continuous stream of unknown musicians plugging unknown stage amplifiers in various states of repair into our power distro. So we have to design for the unexpected situations that can put both them and us in danger. 
Title: Re: Bonding and false positive tests on GFCI
Post by: Geoff Doane on September 03, 2014, 12:12:29 pm
I would imagine that the movie business sets up often enough in locations that would be difficult to drive a ground rod. Concrete streets? Bridges?

FWIW, I usually see movie generators with a ground wire clamped to the nearest fire hydrant on city locations.  I have no idea if that is 'legal' or not, but I would expect it to work as well as a small diametre ground rod.

GTD
Title: Re: Bonding and false positive tests on GFCI
Post by: Stephen Swaffer on September 03, 2014, 01:30:27 pm
NEC 100  Separately derived system= "A premises wiring system whose power is derived from a source of electric energy or equipment other than a service.  Such systems have no direct connection from circuit conductors of one system to circuit conductors of another system, other than connections through earth, metal enclosures, metallic raceways or equipment grounding conductors. "

Premises wiring system="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....."

NEC 250.34 (C) Grounded conductor bonding A system conductor that is required to be grounded by 250.26 shall be connected to the generator frame where the generator is a component of a separately derived system.

The manufacturer has no way of knowing how the end user will use the genny.  I do not see how you can assume that if a genny is manufactured without a neutral bond, that it is always OK to use it that way? 

The only gray area to me is where you draw the line between a premises wiring system and plug and cord connected equipment.  A genny powering a hammer drill is obviously cord and plug connected equipment.  A full blown concert system with lighting, FOH, amp racks and backline supplies is obviously premises wiring.  Personally, I would argue that systems utilized under "plug and cord" connected rules should run off genny receptacles only. perhaps with an extension cord or two-no splitters, spider boxes, etc.  Do I have a ruling in this?  No-but I think a system with wiring splitting off different directions meets the definition of "premises wiring".

That still leaves a hazard for 240 volt equipment.  But there is nothing preventing you from bonding a neutral if the genny is not supplying a system that already has a bond.  Perhaps the NEC should address it-or perhaps it is a specialized enough application that warrants special training for those in your field?  Skilled labor is expected to know how to handle special situations that they may encounter in their job.   
Title: Re: Bonding and false positive tests on GFCI
Post by: Tim McCulloch on September 03, 2014, 02:16:43 pm


That still leaves a hazard for 240 volt equipment.  But there is nothing preventing you from bonding a neutral if the genny is not supplying a system that already has a bond.  Perhaps the NEC should address it-or perhaps it is a specialized enough application that warrants special training for those in your field?  Skilled labor is expected to know how to handle special situations that they may encounter in their job.   

That's exactly what Guy is demonstrating in the pictures.  Training for IATSE brother and sister grips and studio mechanics.
Title: Re: Bonding and false positive tests on GFCI
Post by: Guy Holt on September 03, 2014, 04:10:45 pm
I do not see how you can assume that if a genny is manufactured without a neutral bond, that it is always OK to use it that way?

I'm not.

The only gray area to me is where you draw the line between a premises wiring system and plug and cord connected equipment.  A genny powering a hammer drill is obviously cord and plug connected equipment.  A full blown concert system with lighting, FOH, amp racks and backline supplies is obviously premises wiring.  Personally, I would argue that systems utilized under "plug and cord" connected rules should run off genny receptacles only. perhaps with an extension cord or two-no splitters, spider boxes, etc.  Do I have a ruling in this?  No-but I think a system with wiring splitting off different directions meets the definition of "premises wiring".

I do have a ruling on this and it permits us to run multiple 1200A/3-phase systems without having to adhere to the code dictates of premise wiring. There is a whole other section of the code book  (Article 530 - Motion Picture and Television Studios and Similar Locations) that pertains to portable power (as opposed to temporary premise power) that permits us to use large plugs (400A Camlok)  and large cord  (4 ought) to distribute power from  generators under  "plug and cord" connected rules.

Guy Holt
ScreenLight & Grip
rentals@screenlightandgrip.com
Title: Re: Bonding and false positive tests on GFCI
Post by: Stephen Swaffer on September 03, 2014, 06:10:52 pm
OK, but 1200A/3 phase is a slightly different world and user base than less than 15 kW.  And we are talking pro audio uses here, not studio production.

In the links you posted, reference is made to pro audio requiring bonded neutrals.  They also mention that manufacturers are too busy selling units for standby and home backup to cater to "boutique" uses.

Either enough pro audio users need to start bending the ear of genny manufacturers-since Honda has quiet ones that work well probably should start there.  Otherwise, nothing in code prevents bonding a neutral-in fact code requires it.  It would seem that pursuing rulings allowing running by exceptions for "cord and plug" in situations deemed less safe is counter productive.

Perhaps I misunderstood-but in some of your posts you came across to me as saying in so many words-depending on the genny you have you may be running bonded or unbonded.  What has been discussed and advocated here is that bonding is always necessary-you might have to do it yourself, but it must be there before you power up. 
Title: Re: Bonding and false positive tests on GFCI
Post by: Jonathan Johnson on September 03, 2014, 06:53:25 pm
FWIW, I usually see movie generators with a ground wire clamped to the nearest fire hydrant on city locations.  I have no idea if that is 'legal' or not, but I would expect it to work as well as a small diametre ground rod.

Have you ever seen how THICK the paint can be on fire hydrants? Don't expect a clamp to penetrate that paint -- probably want to scrape down to bare metal. Secondly, how good is the electrical connection between the caps and the hydrant? I would think there could be significant corrosion on the threads. Might want to clamp onto the hydrant body. Then a fall-of-potential test to ensure a good ground might be appropriate.
Title: Re: Bonding and false positive tests on GFCI
Post by: Guy Holt on September 03, 2014, 07:09:34 pm
What has been discussed and advocated here is that bonding is always necessary-you might have to do it yourself, but it must be there before you power up.

I agree. The problem with the EU6500s and the new EU7000s is that they are not easy to bond inside the generator.   I find using a bonded  transformer/distro that steps down the 240V output of the generator to a single large 120V circuit (our lights require large circuits) works best. That way I can use a 100A/120V Shock Block for GFCI protection of the whole distro system downstream (use this link for the IA workshop mentioned above for details: http://www.screenlightandgrip.com/html/481_GFCI_Workshop.html .)

Guy Holt, Gaffer
ScreenLight & Grip
rentals@screenlightandgrip.com
Title: Re: Bonding and false positive tests on GFCI
Post by: Mike Sokol on September 03, 2014, 09:13:02 pm
What has been discussed and advocated here is that bonding is always necessary-you might have to do it yourself, but it must be there before you power up.

+1

I've said it multiple times on this and other forums. All generators feeding distributed power for audio should be earth grounded and have their neutrals bonded. All metal stages and overhead structures (lighting trusses) should also be bonded/connected to this same Ground-Neutral-Earth bonding point. And all 120-volt stage receptacles should be GFCI protected for the safety of the musicians.

For the smaller Honda generators (3KW and under) we tend to run on outside stages, the easiest way to bond the neutral to "ground" is with a Edison plug with a jumper between the Neutral and Ground screws. See my NSZ article about it at http://www.noshockzone.org/generator-ground-neutral-bonding/ (http://www.noshockzone.org/generator-ground-neutral-bonding/) Takes a moment to plug in, doesn't require you to rewire a rental generator, and you won't forget to "unbond" your distro the next time you use it for house power.

All Honda portable generators have a grounding screw or lug of some sort on the frame, which should be run to the ground rod with something like #6 or #8 wire with no hard 90 degree bends. The thick size of the wire and lack of hard bends is really about lightning protection, so don't skimp on the gauge just because you're only running a 2,000 watt genny. If you're doing a double Honda generator setup, this bonding plug should be on the "Companion" generator because the connecting cables are not marked or polarized in any way (bad move from Honda, I think). You can technically run this G-N bonding plug on donor generator, but you'll have a 50/50 chance of creating a reversed "polarity" distro with the frame ground bonded to the hot rather than the neutral leg. Not immediately dangerous, but a code violation and a generally bad idea. 
Title: Re: Bonding and false positive tests on GFCI
Post by: Stephen Swaffer on September 04, 2014, 09:44:05 am
From a manufacturing/code/practical/safety standpoint I really think the best plan for under 15 kW gennys would be to require them to be manufactured with bonded neutrals and GFCI receptacles.  I think that GFCI technology had improved to the point where the "extra" safety of a floating neutral for plug and cord connected is realy a moot point.

For standby use, I would think an exception allowing a second neutral bond for a portable genny under 15 kw providing temporary backup power, provided that the EGC and neutral were sized the same as the ungrounded conductors would provide a safe situation.  Unless somebody can explain how that second bond could create a hazard?  In most of these cases, the genny is going to be connected with SO anyway, so conductors will sized the same. 

That should allow an off the shelf genny to be used safely and in compliance in almost any situation you can come up with?
Title: Re: Bonding and false positive tests on GFCI
Post by: Guy Holt on September 04, 2014, 12:27:40 pm
From a manufacturing/code/practical/safety standpoint I really think the best plan for under 15 kW gennys would be to require them to be manufactured with bonded neutrals and GFCI receptacles… Unless somebody can explain how that second bond could create a hazard? … That should allow an off the shelf genny to be used safely and in compliance in almost any situation you can come up with?

My understanding is that generators, like the EU6500 & EU7000, that are designed for home standby power can not have a Bonded Neutral and a master GFCI because as illustrated in the illustration below, the NEC requires the main service head (panel) of homes to also have Neutral bonded to ground.

(http://www.screenlightandgrip.com/images/generators/SB_GF_HomeService_GFI.jpg)

Where that is the case, if the generator Neutral is also bonded to ground, two parallel paths back to the generator are created for Neutral current, one using the Neutral wire and one using the ground wire. The Neutral current will then flow through both the Neutral and Ground conductor.

(http://www.screenlightandgrip.com/images/generators/SB_GFCI_Diagram.jpg)

Since the Hot and Neutral wires pass through the CT of the ground fault sensor but the Ground wire does not (see illustration above), a master GFCI will sense current imbalance in the 240V single-phase circuit supplying the house panel and trip. In the case of home standby power, bonding the Neutral in the generator will defeat the intent of a master GFCI when the Neutral is bonded in the main service panel. This is why  Honda’s EU generators are designed with Floating Neutrals.

Guy Holt, Gaffer
ScreenLight & Grip
rentals@screenlightandgrip.com
Title: Re: Bonding and false positive tests on GFCI
Post by: Mike Sokol on September 04, 2014, 12:55:27 pm

Since the Hot and Neutral wires pass through the CT of the ground fault sensor but the Ground wire does not (see illustration above), a master GFCI will sense current imbalance in the 240V single-phase circuit supplying the house panel and trip. In the case of home standby power, bonding the Neutral in the generator will defeat the intent of a master GFCI when the Neutral is bonded in the main service panel. This is why  Honda’s EU generators are designed with Floating Neutrals.

Guy Holt, Gaffer
ScreenLight & Grip
rentals@screenlightandgrip.com

All true, but in campgrounds (at least) only the 20-amp receptacles are required to be GFCI protected. The 30 and 50 amp receptacles are exempt from requiring a GFCI. The same goes for portable food trailers with electric ovens/stoves/fryers. Since there's so much leakage to chassis from the equipment design, it would be tripping a 6 mA GFCI all the time. They're considered to be "permanently installed" even though they're connected to 50-amp "carnival" power. In those cases, any interior/exterior 20-amp receptacles are required to have their own GFCI breakers. While this is a standard workaround, it will not protect a customer from getting shocked or electrocuted from an improperly "grounded" food trailer that develops a hot-skin voltage condition due to a broken EGC (safety ground) in its shore power hookup. 
Title: Re: Bonding and false positive tests on GFCI
Post by: Stephen Swaffer on September 04, 2014, 01:18:46 pm
Looking online I can't find anything that says the EU 6500 or 7000 has a master GFCI?  Maybe I am overlooking it.  Typically, I see GFCI's on 20  120 volt receptacles-standard OCP on the 30 and 50 A twistlock 120/240 v receptacle.  In a standby situation, GFCI is not necessary - the POCO 's power is not GFCI protected.

With a master GFCI that would obviously be a problem, but otherwise my thinking is that the only real issue is "objectional"  current in the EGC-which should not be detrimental if it is sized appropriately.  And that would be preferable to uninformed people running gennys without a bond.
Title: Re: Bonding and false positive tests on GFCI
Post by: Jeff Bankston on September 04, 2014, 06:35:01 pm
in los angeles any generator thats built on a set of wheels has to be connected to a ground rod. even all of our contruction site gens had to have a permit from la building and safety and a ground rod driven at the gen. the electrical inspector would come and inspect before we were allowed to use it. a friend runs gens for tv/movie shoots , i will ask him what is required for his 18 wheeler gen rig.
i just talked to my friend about how he ground gens. he said an city inspector always shows up to make sure the gen is grounded. he said he drives a ground rod, finds a cold water pipe and get permission to connect to it, finds a service and gets permission to connect to it, etc. he told me he has seen burned up gens where the neutral was lost and the guy operating the gen didnt ground it. he doesnt know if an inspector had ben to the site or not. he told me he has heard about guys using rubber mats aroumd gens but he doesnt do that because even though it protects you the gen still isnt grounded. heres a foto of him and one of the gens he ran.
Title: Re: Bonding and false positive tests on GFCI
Post by: Scott Holtzman on September 05, 2014, 12:28:34 am
i just talked to my friend about how he ground gens. he said an city inspector always shows up to make sure the gen is grounded. he said he drives a ground rod, finds a cold water pipe and get permission to connect to it, finds a service and gets permission to connect to it, etc. he told me he has seen burned up gens where the neutral was lost and the guy operating the gen didnt ground it. he doesnt know if an inspector had ben to the site or not. he told me he has heard about guys using rubber mats aroumd gens but he doesnt do that because even though it protects you the gen still isnt grounded. heres a foto of him and one of the gens he ran.

My God man, what happened to his face?
Title: Re: Bonding and false positive tests on GFCI
Post by: Jonathan Johnson on September 05, 2014, 01:20:16 am
My God man, what happened to his face?
Now you know where Darth Vader gets his power. :P
Title: Re: Bonding and false positive tests on GFCI
Post by: Jeff Bankston on September 05, 2014, 01:40:31 am
My God man, what happened to his face?
he had a black out ! lol lol lol !
Title: Re: Bonding and false positive tests on GFCI
Post by: Mike Sokol on September 05, 2014, 05:37:13 pm
My God man, what happened to his face?

In a witness protection program?
Title: Re: Bonding and false positive tests on GFCI
Post by: frank kayser on September 05, 2014, 06:04:34 pm
In a witness protection program?
So's the truck...


I guess he's kinda hard to find for a repeat job...
Title: Re: Bonding and false positive tests on GFCI
Post by: Jeff Bankston on September 05, 2014, 06:29:26 pm
simi blacked out
Title: Re: Bonding and false positive tests on GFCI
Post by: Tim McCulloch on September 05, 2014, 06:54:20 pm
So's the truck...


I guess he's kinda hard to find for a repeat job...

Or protecting the confidentiality of the grip truck company, who probably didn't provide direct consent to have their name/logo used.
Title: Re: Bonding and false positive tests on GFCI
Post by: frank kayser on September 05, 2014, 07:56:41 pm
Or protecting the confidentiality of the grip truck company, who probably didn't provide direct consent to have their name/logo used.
Of course that's the serious answer... wasn't nearly as much fun, though!  :P
Title: Re: Bonding and false positive tests on GFCI
Post by: Tim McCulloch on September 05, 2014, 08:25:48 pm
Of course that's the serious answer... wasn't nearly as much fun, though!  :P

It's in Los Angeles and if was on a TV shoot, I'd is all for the Witless Protection Program.  ;)
Title: Re: Bonding and false positive tests on GFCI
Post by: Jeff Bankston on September 05, 2014, 10:02:39 pm
Or protecting the confidentiality of the grip truck company, who probably didn't provide direct consent to have their name/logo used.
i told the guy i was gonna post the foto. i posted the unblacked out foto on the web about a year ago. the guy in the foto also posted the foto. i have lots of fotos of gen trucks and guys i took. i blacked out the company name because i dont want to provide free advertising for a company that i will never rent from. i decided to black out his face for the hell of it. i was going to black out his hands but decided not to. i'll have to send him the blacked out foto. he isnt a member of psw and doesnt go on any forums, not even the drum forum. his drum set is...............................BLACK like mine !

btw its perfectly legal to take a foto of a business with its name and post it on the web. no one has to give consent to have their foto taken when in public and that includes the plumber in the foto "moon" lighting at a food court job.
Title: Re: Bonding and false positive tests on GFCI
Post by: Jeff Bankston on September 06, 2014, 06:57:59 am
heres a foto of me. i did the best i could. i had some ink left over.
Title: Re: Bonding and false positive tests on GFCI
Post by: Jeff Bankston on September 06, 2014, 07:01:59 am
It's in Los Angeles and if was on a TV shoot, I'd is all for the Witless Protection Program.  ;)
witless ! lol !
Title: Re: Bonding and false positive tests on GFCI
Post by: Jonathan Johnson on September 07, 2014, 01:46:51 am
...and that includes the plumber in the foto "moon" lighting at a food court job.

Always nice to see a man praying before his meal.