NFPA decision on new section, NEC 445.20, for small (<15kW) portable generators

Phil Graham

Honorary PhD
Mar 10, 2011
651
1
18
Atlanta, GA
For those of you who use smaller generators (e.g. the Honda EU6500-series) this is a relevant bit of electrical code information. It comes from my tracking for multiple months now on generators for entertainment use as a result of authorship of a series of article on portable generators for FOH magazine:

The NFPA posted the "short" decision on their emergency petition hearing in regards to the new NEC section, NEC 445.20. The petition was to revise the current wording of 445.20 from:


445.20 Ground-Fault Circuit Interrupter Protection for Receptacles on 15 kW or Smaller, Portable Generators. 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 does not have a 125/250 volt locking-type receptacle, this requirement shall not apply.​
to

445.20 Ground-Fault Circuit Interrupter Protection for Receptacles on 15 kW or Smaller, Portable Generators. 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 does not have a 125/250 volt locking-type receptacle or was manufactured or remanufactured prior to January 1, 2015, this requirement shall not apply.​
Page with the link to the PDF of the decision is below:
2013 Standards Council meetings

The PDF of the decision is attached: View attachment SD_13_8_17_d_D13_14_TIA1097_NFPA70.pdf

I've also attached the TIA 1097 amendment requesting the grandfathering:
View attachment 70_NEC-P13_TIALog1097_ballot.pdf

The important paragraph I've quoted below (italics emphasis mine):


The Council has voted to deny the appeal and to not issue TIA No. 1097 or the proposed alternative. The effect of this action is that there will be no exception from complying with the requirement for GFCI protection for those applicable portable generators manufactured or remanufactured before January 1, 2015.​
For jurisdictions that are going to rapidly adopt the new 2014 NEC code cycle, this obviously has substantial implications for many of the small generators currently in the field and used in pro audio, as they (NFPA) explicitly rejected the requests for grandfathering, and the upper wording of NEC 445.20, without grandfathering of any kind, will proceed into effect for 2014 NEC.

I'll let everyone know when I see the full decision if it has more details.
 
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TJ Cornish

Graduate
Jan 13, 2011
1,263
0
0
St. Paul, MN
Re: NFPA petition decision on 2014 NEC 445.20, for portable generators <15kW

The below is the fruit of Phil's work, that he sent to me and a few others, but must have forgotten to post to this thread:


Here's the business part of TIA 1117 that was passed and will make the 2014 code:

445.20 Ground-Fault Circuit Interrupter Protection for Receptacles on 15 kW or Smaller Portable Generators
. 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.


Paraphrasing a reply from a member of the Portable Generator Manufacturers Association: Applicable generators must have GFCIs installed by 1/1/2015. For generators manufactured before that date, using an external GFCI device is acceptable.

Another thread with relevant information:
http://forums.prosoundweb.com/index.php/topic,149292.0.html

Honda produced an EB2000i generator that has a GFCI device that is an inverter-type. The rest of the EB series of generators are not inverter-based. Honda has also released the new EU7000i generator, which does not have GFCI onboard - I'm not sure why. I believe the EU7000 is unbonded like the rest of the EU series.
 
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Phil Graham

Honorary PhD
Mar 10, 2011
651
1
18
Atlanta, GA
Re: NFPA petition decision on 2014 NEC 445.20, for portable generators <15kW

TJ,

Thanks for replying faster than I could, it appears that I did indeed forget to follow up to my own thread here on SFN...

The above text of NEC 445.20 that TJ posted is indeed the text that I received back upon request from the Portable Generators Manufacturers' Association (PGMA), which in turn came out of a previous multiple month dialog with their senior technical advisor as part of an article series on production generators that I wrote for FOH Magazine.

The text of TIA 1117 may be found here, and the ballot for TIA 1117 can be found here. The balloting document includes some of the comments of those members who disagreed with the emergency nature of the petition, and is thus useful for coloring the decision for those interested in 2013's substantial drama for portable generators under 15kVA.
 
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Guy Holt

Freshman
Aug 4, 2014
4
0
0
Re: NFPA petition decision on 2014 NEC 445.20, for portable generators <15kW

Here's the business part of TIA 1117 that was passed and will make the 2014 code: generators must have GFCIs installed by 1/1/2015. For generators manufactured before that date, using an external GFCI device is acceptable
That the NFPA finally relented and grandfathered generators manufactured before 1/1/2015 (as long as they are used with separate GFCIs) pulled us back from the brink of disaster, NEC 445.20, as written, may still spell doom for the Honda EU6500 as well as the new EU7000. If you follow the argument by the Technical Director of the PGMA in TIA 1117 that was voted into the 2014 Code, NEC 445.20 in its final form “would allow the continued use of existing portable generators by allowing the use of external GFCI devices to provide equivalent protection.” This spells doom for the Honda EU6500 and the new EU7000 because, without Bonded Neutrals, separate GFCIs will not provide “equivalent protection” on these generators.

Tests recently conducted by The Construction Safety Association of Ontario (CSAO) uncovered significant problems in using GFCIs on portable generators with Floating Neutrals. Since the CSAO conducted their tests to determine the effectiveness of GFCIs used on portable generators in typical construction scenarios, they did not test the EU6500 directly, but their findings are applicable to it. The GFCIs used in the CSAO tests were the very portable use cord sets that incorporate listed GFCI protection for personnel described in NEC 445.20. In the tests a rheostat was used to simulate a current leak to Ground (Ground Fault). Generators connected to GFCIs were tested on wet ground, dry surfaces, and an insulated surface (the back of a pickup truck). In addition, tests covered variable grounding conditions: proper earth ground, earth ground with some resistance, no earth ground. Based upon their tests, the CSAO report drew the following conclusions (use this link for the complete report):

1) In the case of Floating Neutral generators, where the Neutral is not bonded or grounded but "Floating", GFCIs failed to trip even when the current leak reached higher than acceptable levels. Without a Neutral bond, electricity did not leak to ground to trip the GFCI - creating a possibly hazardous situation in the event of a second Fault if the GFCI is not located properly in the distribution system.

2) GFCI test buttons functioned regardless of the GFCI's operability. The buttons cannot be used to test the effectiveness of GFCIs or grounding.

3) Proper placement of GFCI protection is different for Floating Neutral and Bonded Neutral generators.

The CSAO report author concluded that simply using a GFCI on a Floating Neutral generator will not ensure a safe system, and can in fact be misleading. That is because a GFCI will not operate reliably if one side of the winding is not bonded to the generator frame. Without a bond Fault Current has no path back to the winding to complete the circuit. Only when Neutral is bonded to Ground, will current go to Ground to complete the circuit when there is a current leak. In other words, a complete circuit is required to create an imbalance and cause the GFCI to trip.
SB_GFCI_Diagramdetail.jpg

GFCI test circuits are misleading when they are used on Floating Neutral generators because they can produce a false positive. On a Floating Neutral generator, the test button will draw power from the Hot through the CT and back through the CT again to the Neutral via a Current Limiting Resister. The discrepancy caused by the Current Limiting Resister in the test circuit (illustrated above) will initiate the GFCI to trip even though there is in fact no Ground Fault Circuit for Fault Current to go to if there were a Fault. The false positive received by GFCI test circuits on ungrounded Floating Neutral generators does nothing to eliminate faulty equipment.

Where separate GFCIs will clearly not provide “equivalent protection” on the EU6500, it does not qualify for the exemption to NEC 445.20 that requires that “All 125-volt, single-phase, 15-and 20-ampere receptacle … either shall have ground-fault circuit-interrupter protection for personnel … or shall not be available for use when the 125/250-volt locking-type receptacle is in use.” This spells doom for the single phase Honda inverter generator because what good is a generator that can’t supply both 120V and 240V at the same time.

Guy Holt, Gaffer
ScreenLight & Grip
[email protected]
 

TJ Cornish

Graduate
Jan 13, 2011
1,263
0
0
St. Paul, MN
Re: NFPA petition decision on 2014 NEC 445.20, for portable generators <15kW

That the NFPA finally relented and grandfathered generators manufactured before 1/1/2015 (as long as they are used with separate GFCIs) pulled us back from the brink of disaster, NEC 445.20, as written, may still spell doom for the Honda EU6500 as well as the new EU7000. If you follow the argument by the Technical Director of the PGMA in TIA 1117 that was voted into the 2014 Code, NEC 445.20 in its final form “would allow the continued use of existing portable generators by allowing the use of external GFCI devices to provide equivalent protection.” This spells doom for the Honda EU6500 and the new EU7000 because, without Bonded Neutrals, separate GFCIs will not provide “equivalent protection” on these generators.

...

Where separate GFCIs will clearly not provide “equivalent protection” on the EU6500, it does not qualify for the exemption to NEC 445.20 that requires that “All 125-volt, single-phase, 15-and 20-ampere receptacle … either shall have ground-fault circuit-interrupter protection for personnel … or shall not be available for use when the 125/250-volt locking-type receptacle is in use.” This spells doom for the single phase Honda inverter generator because what good is a generator that can’t supply both 120V and 240V at the same time.

Guy Holt, Gaffer
ScreenLight & Grip
[email protected]
For our purposes - portable power - this would easily be solved by Honda bonding the generator, or at the very least, a selectable bond, so that it could be unbonded when providing backup power for a system with a bond external to the generator, but bonded when used for portable power, enabling GFCIs and OCPDs to work.

I was very surprised that Honda for the EU7000 produced a presumably wonderful engine platform, but with essentially no difference on the output side in light of the new code changes. Honda has been clearly aware of these issues for a long time.
 
Re: NFPA petition decision on 2014 NEC 445.20, for portable generators <15kW

That the NFPA finally relented and grandfathered generators manufactured before 1/1/2015 (as long as they are used with separate GFCIs) pulled us back from the brink of disaster, NEC 445.20, as written, may still spell doom for the Honda EU6500 as well as the new EU7000. If you follow the argument by the Technical Director of the PGMA in TIA 1117 that was voted into the 2014 Code, NEC 445.20 in its final form “would allow the continued use of existing portable generators by allowing the use of external GFCI devices to provide equivalent protection.” This spells doom for the Honda EU6500 and the new EU7000 because, without Bonded Neutrals, separate GFCIs will not provide “equivalent protection” on these generators.

Tests recently conducted by The Construction Safety Association of Ontario (CSAO) uncovered significant problems in using GFCIs on portable generators with Floating Neutrals. Since the CSAO conducted their tests to determine the effectiveness of GFCIs used on portable generators in typical construction scenarios, they did not test the EU6500 directly, but their findings are applicable to it. The GFCIs used in the CSAO tests were the very portable use cord sets that incorporate listed GFCI protection for personnel described in NEC 445.20. In the tests a rheostat was used to simulate a current leak to Ground (Ground Fault). Generators connected to GFCIs were tested on wet ground, dry surfaces, and an insulated surface (the back of a pickup truck). In addition, tests covered variable grounding conditions: proper earth ground, earth ground with some resistance, no earth ground. Based upon their tests, the CSAO report drew the following conclusions (use this link for the complete report):

1) In the case of Floating Neutral generators, where the Neutral is not bonded or grounded but "Floating", GFCIs failed to trip even when the current leak reached higher than acceptable levels. Without a Neutral bond, electricity did not leak to ground to trip the GFCI - creating a possibly hazardous situation in the event of a second Fault if the GFCI is not located properly in the distribution system.

2) GFCI test buttons functioned regardless of the GFCI's operability. The buttons cannot be used to test the effectiveness of GFCIs or grounding.

3) Proper placement of GFCI protection is different for Floating Neutral and Bonded Neutral generators.

The CSAO report author concluded that simply using a GFCI on a Floating Neutral generator will not ensure a safe system, and can in fact be misleading. That is because a GFCI will not operate reliably if one side of the winding is not bonded to the generator frame. Without a bond Fault Current has no path back to the winding to complete the circuit. Only when Neutral is bonded to Ground, will current go to Ground to complete the circuit when there is a current leak. In other words, a complete circuit is required to create an imbalance and cause the GFCI to trip.

GFCI test circuits are misleading when they are used on Floating Neutral generators because they can produce a false positive. On a Floating Neutral generator, the test button will draw power from the Hot through the CT and back through the CT again to the Neutral via a Current Limiting Resister. The discrepancy caused by the Current Limiting Resister in the test circuit (illustrated above) will initiate the GFCI to trip even though there is in fact no Ground Fault Circuit for Fault Current to go to if there were a Fault. The false positive received by GFCI test circuits on ungrounded Floating Neutral generators does nothing to eliminate faulty equipment.

Where separate GFCIs will clearly not provide “equivalent protection” on the EU6500, it does not qualify for the exemption to NEC 445.20 that requires that “All 125-volt, single-phase, 15-and 20-ampere receptacle … either shall have ground-fault circuit-interrupter protection for personnel … or shall not be available for use when the 125/250-volt locking-type receptacle is in use.” This spells doom for the single phase Honda inverter generator because what good is a generator that can’t supply both 120V and 240V at the same time.

Guy Holt, Gaffer
ScreenLight & Grip
[email protected]
Here is the link to the CSAO report (pdf). The other big takeaway from that report is that in addition to bonding neutral to the generator frame, it is also important to ground the generator frame.
 

Phil Graham

Honorary PhD
Mar 10, 2011
651
1
18
Atlanta, GA
Re: NFPA petition decision on 2014 NEC 445.20, for portable generators <15kW

Guy, et al.,

On pp. 10 of the Canadian report you cited in your post and on your website, the wording indicates that a 0.6mA fault current to ground was observed. This, of course, would not trip a GFCI that was thresholded at 5mA. The exact wording that follows in the Canadian document is:

"Current still flowed as the ground leak was set at full. Since the GFCI failed to trip in this test, further testing with floating neutral generators was terminated."
Briefly playing the devils advocate here, the wording above not conclusive that the GFCI failed to do its job (i.e. trip at 5mA fault current). Now, if the wording said that the fault current increased to above 5mA and the GFCI did not trip, then I this would be clear cut. The reason that the GFCI did not trip in the first case is that there was not a sufficient fault current return path to exceed the 5mA threshold. In the case of this primary fault, insufficient current flows to trip the GFCI as there is no current path. This is not an unsafe condition for the generator user, presuming we are comfortable with the 0.6mA leakage current level.

The Canadian report acknowledges as much on pp. 14:

"When the electrical system does not have reference to ground, GFCIs mounted on the generator do not work. With one fault, not enough current leaks to ground to be considered a hazard. Thus, in a floating neutral circuit, workers are not endangered by electrocution from current going to ground as long as there is only one fault in the system."
But the report then goes on to discuss the dual fault condition on pp. 15:

"However, with two faults in the system, one on the neutral and one on the hot side, it is possible that the floating neutral system can become grounded. In that case, workers without properly located GFCIs can be electrocuted... Testing showed that in a two fault system, the placement of the GFCI is critical. The GFCI must be placed between the two faults in order to function..."
In my extensive email discussions with PGMA, I made essentially the same double fault case argument as above, though the Canadians crafted it more succinctly.

I think you can make a further argument that the as-chosen wording for 445.20 going forwards is in violation of NEC 250.4(B)(4) "General Requirements of Grounding and Bonding - Ungrounded Systems." From the 2014 NEC code draft:

(4) Path for Fault Current. Electrical equipment, wiring, and other electrically conductive material likely to become energized shall be installed in a manner that creates a low impedance circuit from any point [emphasis mine] on the wiring system to the electrical supply source to facilitate the operation of overcurrent devices should a second ground fault from a different phase occur on the wiring system. The earth shall not be considered as an effective fault-current path."
I also think an argument could be made for the TIA 1117 wording for NEC 445.20 as violating 2014 NEC 250.21(B)(1). Again from the 2014 NEC code draft:

"Ungrounded alternating current systems as permitted in 250.21(A)(1) through (A)(4) operating at not less than 120 volts and 1000 volts or less shall have ground detectors installed on the system. [ROP 5–63]"
Said detectors are to indicate the first ground fault condition of a normally ungrounded system, so that the operator can address this before a second fault condition causes a problem.
 
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Phil Graham

Honorary PhD
Mar 10, 2011
651
1
18
Atlanta, GA
Re: NFPA petition decision on 2014 NEC 445.20, for portable generators <15kW

Guy,

When I wrote about "floating neutral" generators as part of an article series in FOH magazine, this is how we ended up wording the sidebar to address these finicky creatures:

There are millions of small generators, typically less than 10-kW, that are known in industry terminology as “floating neutral” generators. The Honda EU6500is (Figure 1) is an example of such a floating neutral generator. Essentially all inverter-based generators, and many home backup-oriented generators, adopt this configuration. Floating neutral simply means the generator neutral is not bonded to the generator frame or the grounding conductor.

When these generators are used for house backup, the bonding is performed by the home’s panel, rather than on the generator. The home, generator, and power company neutrals are bonded at a single point in the home’s main service panel. The grounding conductor(s) are also bonded to the neutrals at this same point in the panel. This provides the fault current return path, via the generator neutral, for the home's branch circuits when running off generator power.

When floating neutral generators are used in a standalone setting, they are intended to be operated without grounding. The lack of conduction to Earth, combined with the lack of neutral to ground bonding means that there is no ground fault-current return path, so no current flows in the event of a single fault to ground. Standalone operation without a ground rod limits code-compliant generator operation to “cord-and-plug-connected equipment” per NEC 250.34.

With no current return circuit, a fault event does not present a shock hazard, barring the presence of a secondary current path (i.e. second fault). Because there is no fault current return path, the floating neutral configuration will not trip a conventional circuit breaker. Thus, if equipment attached to a floating neutral generator experiences a fault event, there will be no breaker tripping to indicate the fault’s presence.

Operation of a floating neutral generator in the pro audio context first requires external bonding of the neutral and ground, similar to the circumstance of using these generators for home backup service. Details of this bond are discussed in NEC 250.30. After the bond is established, a low impedance fault current path via the neutral is created. At this point the generator frame can then be tied to a ground rod, and the generator operated as a SDS. As an example, the Honda EU6500is in Figure 1 can be externally bonded, connected to earth via a GEC and operated as a SDS.

Finally, note that some small inverter generators do not hold their neutral at ground potential, but rather have the hot +60Vrms to ground, and the neutral -60Vrms to ground. Thus, these generators cannot have a neutral to ground bond, and are only intended to operate cord and plug connected equipment.
 

TJ Cornish

Graduate
Jan 13, 2011
1,263
0
0
St. Paul, MN
Re: NFPA petition decision on 2014 NEC 445.20, for portable generators <15kW

Finally, note that some small inverter generators do not hold their neutral at ground potential, but rather have the hot +60Vrms to ground, and the neutral -60Vrms to ground. Thus, these generators cannot have a neutral to ground bond, and are only intended to operate cord and plug connected equipment.
Phil, I'm interested to know if you have any specific examples of this. It's actually possible that I have contributed to misinformation here - I believe I did measure an eu2000i that I used once upon a time as a +/- 60V to ground system, but I believe I read somewhere that this was likely due to coupling capacitors, and that bonding the eu2000 is actually not problematic.
 

Guy Holt

Freshman
Aug 4, 2014
4
0
0
Re: NFPA petition decision on 2014 NEC 445.20, for portable generators <15kW

But the report then goes on to discuss the dual fault condition on pp. 15…
In an IATSE Local 481 workshop that I give, we simulate a double fault situation (like what would happen if a defective cord was dragged through the mud) with a unbonded Honda EU6500 to see what would happen.

SB_Header.jpg

We first create a fault in the Hot by attaching a jumper cable from the Hot pocket of a little patch box I made up to the input of a Fault Simulator that basically consists of a variable 16-25k Ohm resister. So that we can obtain precise measurements of leakage current, we attach a second jumper from the output of the Fault Simulator to the input of a Fluke 1587 Insulation Multimeter, and then a third jumper cable from the output of the Fluke 1587 to one of two ground rods we drive.

481_GFCI_Wkshp_Demo_Set_Up_Sm.jpg

To create a second fault we jumper from the neutral pocket of the patch box to the input of a box with just a switch and another jumper from the output of the switch box to another ground rod. We start by opening the switch on the switch box and closing the Fault Simulator (maximum resistance) so that we can regulate the current leaking to earth.
481_GFCI_Wkshp_Gen_SetUp3.jpg

When we fired up the generator and supply power to our fault circuit, we see immediately on the Fluke 1587 that there is 4.9mAmps leaking to earth. Clamping a Megger DCM300E Leakage meter onto the jumper going from the Neutral pocket of the patch box to the second ground rod, we see that the Fault Current is returning to the generator's windings through the second fault that we established on the Neutral as depicted in the illustration below (click on the image to enlarge it, then hit the back button to return to the forum.)

SB_Test_Double_Fault.jpg

As we gradually reduce the resistance of the Fault Simulator by turning its' rheostat, the leakage current begins to rise. When the Fault Simulator is all the way open (minimum resistance) we get a clear Ground Fault of 7.9mAmps (according to the readout of the Fluke) and the breaker does not trip. Closing the switch on the Switch Box so that there is only one fault in our system, the current leakage to earth stops. Opening the switch on the switch box, the leak begins again.

The purpose of this demonstration is to show that a double fault - one in the Hot, and a second in the Neutral - creates a potentially hazardous situation because a path (circuit) now exists for fault current to return to the generator windings even though there is no neutral to ground bond. 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. And, as demonstrated if either of the faults is of a high resistance, the current will not be high enough to trip the breaker, and the individual will receive a sustained shock that can be potentially fatal. The Figure below illustrates why an individual receives a shock when there are two faults in a distribution system.
SB_GF_FG_Shock_Illustration.jpg

The reason NEC 445.20 is so adamant about there being GFCI protection when a un-bonded generator supplies 240V is that double Faults with Floating Neutrals are especially hazardous. Without a Neutral/Ground bond, as illustrated below, a double fault condition like that illustrated below can expose an individual touching faulty equipment to 240 volt potential.
SB_2Fault240V_Exposure.jpg

What I find particularly scary about the double fault situation in my workshop demonstration is that a GFCI plugged into the 120V receptacle of the generator offers no protection since, as the illustration above clearly depicts, the fault current returns to the neutral via the second fault before passing back through the GFCI Current Transformer.

Is the Ground Fault current of 7.9mAmps in this demonstration a hazard? It is on the threshold of being painful but not potentially fatal because an individual experiencing 7.9mAmps still has muscular control and will be able to remove them selves from the source of the shock. But, will an individual coming into contact with this ground fault receive 7.9mAmps? All the information you need is given here. If you don’t know how to answer this question I would suggest you use this link to read the summary of my IA workshop because someone coming between the double faults in that situation would be electrocuted without the GFCI even sensing a leak of any kind.

Guy Holt, Gaffer
ScreenLight & Grip
[email protected]
 
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TJ Cornish

Graduate
Jan 13, 2011
1,263
0
0
St. Paul, MN
Re: NFPA petition decision on 2014 NEC 445.20, for portable generators <15kW

Guy - thanks for your work both here and at PSW. One small suggestion - for your second drawing entitled "Floating Neutral Generator", a legend that indicates what the faults are would be helpful - i.e. the yellow star is the fault, and completing your blue arrows to show the fault circuit. The drawing is a little hard to follow without that.
 

Phil Graham

Honorary PhD
Mar 10, 2011
651
1
18
Atlanta, GA
Re: NFPA petition decision on 2014 NEC 445.20, for portable generators <15kW

Guy - thanks for your work both here and at PSW. One small suggestion - for your second drawing entitled "Floating Neutral Generator", a legend that indicates what the faults are would be helpful - i.e. the yellow star is the fault, and completing your blue arrows to show the fault circuit. The drawing is a little hard to follow without that.
TJ,

Those graphic icons look like the ones from Mike Holts' classes, so there's a decent chance that Guy cannot change them.
 

Phil Graham

Honorary PhD
Mar 10, 2011
651
1
18
Atlanta, GA
Re: NFPA petition decision on 2014 NEC 445.20, for portable generators <15kW

What I find particularly scary about the double fault situation in my workshop demonstration is that a GFCI plugged into the 120V receptacle of the generator offers no protection since, as the illustration above clearly depicts, the fault current returns to the neutral via the second fault before passing back through the GFCI Current Transformer.

Is the Ground Fault current of 7.9mAmps in this demonstration a hazard? It is on the threshold of being painful but not potentially fatal because an individual experiencing 7.9mAmps still has muscular control and will be able to remove them selves from the source of the shock. But, will an individual coming into contact with this ground fault receive 7.9mAmps? All the information you need is given here. If you don’t know how to answer this question I would suggest you use this link to read the summary of my IA workshop because someone coming between the double faults in that situation would be electrocuted without the GFCI even sensing a leak of any kind.

Guy Holt, Gaffer
ScreenLight & Grip
[email protected]
Guy,

Have you ever had any interaction with PGMA's technical people? If not, send me a PM, and I'll put you in contact with their technical advisor. You have taken my theoretical discussion of a second fault and physically implemented it in the field. That might provide further discussion for points for PGMA to think about the limitations to fault protection.
 

Guy Holt

Freshman
Aug 4, 2014
4
0
0
Re: NFPA petition decision on 2014 NEC 445.20, for portable generators <15kW

In my extensive email discussions with PGMA, I made essentially the same double fault case argument as above, though the Canadians crafted it more succinctly… I think you can make a further argument that the as-chosen wording for 445.20 going forwards is in violation of NEC 250.4(B)(4) "General Requirements of Grounding and Bonding - Ungrounded Systems."… I also think an argument could be made for the TIA 1117 wording for NEC 445.20 as violating 2014 NEC 250.21(B)(1).
I spoke to someone who was part of the Code Panel 13 drafting of NEC 445.20. According to this individual, the requirement for GFCIs on 125V circuits on a generator where the 240V circuit is in use as well was discussed only in the context of the generator serving as home back up power. In that application the bond between the ground and neutral in the service head of the house will assure the reliable operation of GFCIs on the generator. The use of a generator in a stand-alone application as a separately derived system was never discussed. Even though this individual recognized the fact that in a stand-alone situation (without a Ground-Neutral Bond) GFCIs will not operate reliably and therefore not provide “equivalent protection”, NEC 445.20 as written will require their use none-the-less on 120V circuits in pro-sound applications when a “spider box” is used on the 240V receptacle and motion picture lighting applications when a 240V lighting load (like a 4k HMI) is used on the 240V receptacle. The only inherent danger here is that the false positive of GFCI test circuits in these situation (that I discussed above) will create a false sense of security in the user of the devices.


One approach that will satisfy the “equivalent protection” intent of NEC 445.20 is to use a transformer to step-down the 240V output to 120V instead of splitting it as a spider box does.


As a separately derived system, a transformer typically bonds neutral to ground to create a low impedance path (illustrated above (click on the image to enlarge it, then hit the back button to return to the forum.)) for fault current back to the transformer windings thereby assuring the reliable operation of GFCIs.


A cart outfitted with 60A Transformer/Distro, 100A Shock Block, and 4/2.5kw & 1800W ballasts.
Note: that the 1800W Ballast is plugged directly into a 60A Woodhead w/3 20A circuits.

If you add a breaker (as we do on the Transformer/Distros we make for the Honda EU6500 – pictured above) you have reliable over-current protection as well.


Guy Holt, Gaffer
ScreenLight & Grip
[email protected]
 

Phil Graham

Honorary PhD
Mar 10, 2011
651
1
18
Atlanta, GA
Re: NFPA petition decision on 2014 NEC 445.20, for portable generators <15kW

...One approach that will satisfy the “equivalent protection” intent of NEC 445.20 is to use a transformer to step-down the 240V output to 120V instead of splitting it as a spider box does...

Guy Holt, Gaffer
ScreenLight & Grip
[email protected]
Guy,

In my discussions with PGMA, I referred them to your transformer based SDS solution as an example of how to tackle our circumstances. It was clear that they were not well informed on our use cases in pro audio, and the likelihood of some of the other possible fault states in our use context. I also suggested that they approach Honda about creating a listed bonding kit for those who know that they need such a thing.

The reality is that the PGMA members are busy selling lots and lots of generators into home backup and/or cord and plug connected applications. They don't seem interested in complicating the connection procedure in those circumstances, regardless of our boutique needs in pro audio or the film industry. The floating neutral configuration allows them to produce generators that are bonded in the home backup case, and provide a reasonable degree of protection against faults in the cord and plug use case.