Ground Fault Systems.

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brian john

brian john

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Leesburg, VA
For the 3rd time this year I have had a call to investigate a tripping Ground Fault Protection (GFP) on a main switch. In each case this cause of the tripping has been the same.

In each case there were multiple neutral to ground connections downstream from the main neutral ground bond. Two of the distribution systems were a main switch with a distribution trough feeding multiple feed through revenue meters and/or CTs cabinets, then to the end user's disconnect.

The neutrals were left mounted to the back box in the meters/CT's cabinets and then in the end users disconnect the neutral was bonded a 3rd time (at the main in the Meter/CT cabinet and in the disconnect).

In one case the GFP was set at 100 amps, one case at 400 amp and another at 600 amps. That is a lot of ground current in every case that is required to trip the GFP.

While grounding can be difficult to understand for some, this is BASIC GROUNDING, you bond the neutral to ground at the main service NOT anywhere down stream of the main. If you ground down stream from the main you can have ground current that can result in tripping the mains's GFP and under fault conditions you can negate the effectiveness of the GFP.

All systems were installed by reputable EC's that supposedly have qualified electricians.
 
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The installer sees that the manufacturer has provided that "green screw" and thinks he has to use it. This is a very common installation error. Maybe it would be better if you had to buy the main bonding jumper as an accessory to the panel instead of having one supplied with every panel that is listed as "suitable for use as service equipment".
 
don_resqcapt19 said:
The installer sees that the manufacturer has provided that "green screw" and thinks he has to use it. This is a very common installation error. Maybe it would be better if you had to buy the main bonding jumper as an accessory to the panel instead of having one supplied with every panel that is listed as "suitable for use as service equipment".
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I agree 100%
 
I don't agree.

The dumbing down of America.:roll: We shouldn't have to come up with workaround solutions just because some installers are idiots. I shouldn't have to order disconnects with or without neutral kits that come with or without bonding screws.

Maybe the better solution would be to call the so-called reputable EC and inform him his guys might need a refresher course on grounding and bonding.
 
Not too long ago, I noticed a GF protected MDP with the grounds terminated on the wrong side of the CT.
The electrician didn't believe me, contacted the distributor where the factory rep advised all was connected properly.
After energizing & tripping, the made the corrections.
"Dumbing down" does not end at the bottom of the food chain.
 
I have posted before inspectors requiring EGC to be terminated on the wrong side.

I will teach any contractors or inspectors that want classes. I try on site to explain to as many that will listen when we are testing GFPs.
 
GF Trip

GF Trip

We had a motor with 400A GF feeder Breaker randomly tripping:-?. Used megger, meters and termination inspections to locate problem to no avail.. have 500v cable tester also...random start up trips... 100A setting at .7s..

Finial location of problem was through local motor company who Hi Potentialed the motor and the leads. With wires isolated, testing showed on the Leads: A ph @ 3800V = .5 microamp leakage. B ph @ 2900V = .4 microamp C ph @ 1200V = 1.6 microamp

Pulled wires. Damaged 8? years ago when installed. in the middle of run. Arc marks on wire.. chocked it up to vibration, humidity and solar alignments of Pluto and Mars as to when the inrush current and other factors would cause trip.:cool:
 
Goroon said:
We had a motor with 400A GF feeder Breaker randomly tripping:-?. Used megger, meters and termination inspections to locate problem to no avail.. have 500v cable tester also...random start up trips... 100A setting at .7s..

Finial location of problem was through local motor company who Hi Potentialed the motor and the leads. With wires isolated, testing showed on the Leads: A ph @ 3800V = .5 microamp leakage. B ph @ 2900V = .4 microamp C ph @ 1200V = 1.6 microamp

Pulled wires. Damaged 8? years ago when installed. in the middle of run. Arc marks on wire.. chocked it up to vibration, humidity and solar alignments of Pluto and Mars as to when the inrush current and other factors would cause trip.:cool:
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That is still better than politics. :grin:



I have posted on this site not too long ago, that 80% of standard installations seem to have either grounding or bonding issues. In todays setting, with education of all kinds available for free and on the internet which negates the fact they do not have time to go to class, it is just short of criminal that this still occurs.

EDUCATION and CONTINUING EDUCATION are not pursued enough by the student or the jurisdiction that is in charge of the electricians.
 
While I am at it...
Another argument I hear is the contractor says he cannot afford to pay for the education of all his men.

Hello, it is not the contractors obligation to pay for his men to be educated. It is the men's obligation to offer the contractor his skills, which includes education.



If the skill set the contractor is demanding may be more than the standard, then some kind of compensation may be necessary.

ME, ME, ME, ME

I think it is time for a reeducation of the general population to start thinking like team players, maybe things would get a little better.
 
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You do not need to pay for education, there is a wealth of data available. I have a 2" binder from pre-Internet days loaded with GFP literature from manufactures plus tons of books and maybe 10 binders with data I have downloaded from the Internet with information ranging from grounding to phantom voltages.

I have offered these for free to my men, few if any bother to take a copy, but the copies of Easy Rider and Tattoo Monthly disappear. I use to send a weekly letter home for their education, safety tips, grounding, test equipment use, ETC. I would ask the men if they read this stuff and 99% said their wives open the checks and trash the infomercial junk that accompanies the check.

I also send my men to classes some of these courses were on the weekend and several wanted OT pay if they attended a class I was paying for. I offered to pay for college classes and the same men said only if they could attend during work hours or be paid OT.

Our local offers NEC classes when I suggested attending these classes some guys suuggested a paid class as they were during work hours and closer.
 
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For those who are in the local or are local contractors, it is not the contractor's responsibility to educate the men. It is the local's responsibility, and the men's responsibility.

Maybe the thought should be...jeez, I wonder if the contractor is going to be hurt if I take a day of work to educate myself.

It is relative to driving:

There are two way streets, one way streets, and then there are dead ends!
 
I have to say that bond screw is the cause of many failures, not installed when it should be and installed when it should not be, that is why all panel covers must be removed for inspection
 
I think that there should just be a little signature card in each panel, with a place for the bonding screw next to it "bonding screw installed by _______/not installed by ______________, date ___________"
 
bonding screw current

bonding screw current

Have you ever seen any data on what kind of current can pass through the few threads that are touching with a bonding screw? Never thought much about it before, but just kind of curious what that does to the fault path.
 
mivey said:
Have you ever seen any data on what kind of current can pass through the few threads that are touching with a bonding screw? Never thought much about it before, but just kind of curious what that does to the fault path.
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Enough to trip a 200 amp main CB so at a minimum 1600-2000 and Upwards.
 
brian john said:
Enough to trip a 200 amp main CB so at a minimum 1600-2000 and Upwards.
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But it may not be limited by any breaker. If a service conductor faults to the enclosure I expect that 10/32 machine screw to become a fast acting fuse and give up it's roll as a bonding means.
 
iwire said:
But it may not be limited by any breaker. If a service conductor faults to the enclosure I expect that 10/32 machine screw to become a fast acting fuse and give up it's roll as a bonding means.
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We had just such an incident here in the area I work in.

The lineside fault (lineside of a 4000A, 480V service), disintergrated the main bonding screws of several of the service disconnects.

I just happen to have a picture of the event as well... ;)

CityCenterOct2103-Accident018.jpg
 
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