Well I’ll go first, I get a little nervous without driving a few rods. I go overboard on my grounding on r-mix plants, in some fashion due to the silo makes a real big target for lightning.
ETA as far as operating, no, safety in my rough and tumble world of concrete, I will say yeah. A few copper clad rods flogged in the ground are cheap and easy.

 

Well I’ll go first, I get a little nervous without driving a few rods. I go overboard on my grounding on r-mix plants, in some fashion due to the silo makes a real big target for lightning.
ETA as far as operating, no, safety in my rough and tumble world of concrete, I will say yeah. A few copper clad rods flogged in the ground are cheap and easy.

100% agree with that aspect of grounding.

 

I'm certain that I have always know that the system will operate without grounding.

 

Brian you should have put a finer point on it. Does connecting to a ground rod help or cause breakers to trip? No. Will connecting to the ground rod help with lightning protection, voltage stabilization, & cause the POCO fuse to blow if the xfmr shorts to the secondary? I believe so.

 

System ground and lightning ground protection are different animals.

 

Yes, for voltage stability as noted in both NEC 250.4(A)(1) and CEC 10-002 a).

 

Please explain how driving an electrode provides voltage stability?

 

What the heck, there's no ducking smilie?

 

If you have no grounding electrode, what happens in an open neutral situation?

 

Well, depending on where the neutral is broken, and the condition of your ground conductors, you might have neutral current on both a portion of your neutral and your ground conductor.

But that's not normal operation of your electrical system.

 

If that was true, then how could we have ungrounded systems, resistance and impedance grounded systems?

 

...or a waterproof flashlight?

 

I don't think the rods are necessary for a system to function, but when the fecal matter strikes the oscillating device I'd be wishing they were there.

 

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Holt is long winded but man you forget how knowledgeable he is.

 

IMO, the purpose of the grounding electrode conductor is simply to drain any voltage spikes to the earth rather than thru the house. Ground rods in most areas are not very useful but a concrete encased electrode can be beneficial to accomplish this goal.

Brian, I have had many electricians tell me that the grounding electrode conductor is there in case the neutral fails.... And these were licensed guys. Grounding is probably the hardest thing to understand in the nec

 

I have had many electricians tell me that the grounding electrode conductor is there in case the neutral fails.

Find a post, article, or story where the ground rod came to the rescue and saved equipment if it happens it is rare..

I agree. The ground rod does not come to the rescue of a severed neutral situation.

And to add another story, about 15 years ago my dad called during a winter storm and asked what to do because a big limb fell, taking out the top wire of his 1949 60 amp service drop. You know, the old three separate wires on ceramic insulators. The top wire is the Neutral. I asked him if some lights got dim and others bright. Nope, all is working normally. He could get by without lights, but the furnace was nice to run. I asked him to turn on some specific loads I remembered. Everything worked without lights (incandescent of course) dimming or brightening. Well, I guess the neutral is connected through your water and/or gas pipes! Just limit your use in case whatever is the circuit now gets disrupted. If it was neutral through a ground rod only, no way would this work so well. It took several days before Va Power came by. I just happened to be visiting and watched as they reconnected the existing copper wire back together in a mid air splice. I think that wire was only 8 AWG solid.

 

Well, everyone knows electricity wants to go to ground

 

Grounding is not necessary as there are ungrounded systems.

 

..and a floating wye (no ground rod) would still work.

 

I think it is soooooooo important that the NEC requires a ground rod to be at less than 25 ohms resistance to ground and if it is not you need two rods. But don't bother testing the second rod as it doesn't matter, it will be fine, hahahahahah,

 

Just drop two rods & be done with it.

 

Depends on the type of system. If theres controls involved an ungrounded neutral could cause unpredictable actions in control circuits. In distribution systems it will not have an effectect in unbalanced systems it can cause overheating if the sum of the loads not equal 0
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Yep, we had a site that was impedance grounded and the UPS's worked but would not parallel.

 

....

 

Well sure, in an intact service, excluding the supply, and an installation in good repair, it will work just fine without an electrode.


Have you ever clamped a GEC and found current flowing on it?

 

As part of my job I do grounding investigations, so yes

 

I am not super solid on this but I think that the grounding system and a low-impedance ground are important for operation of MOV type surge protection that shunts surges to ground.

I did not think that's what they're talking about in 250.4, I think the idea is, when one of the current carrying conductors on the system is at ground potential, the phase-to-ground potential is limited, so in the event of a strike to ground or a utility high voltage fault to ground, less damage occurs to the system and to the building and the people in it.

True or false?

 

I did not think that's what they're talking about in 250.4, I think the idea is, when one of the current carrying conductors on the system is at ground potential, the phase-to-ground potential is limited, so in the event of a strike to ground or a utility high voltage fault to ground, less damage occurs to the system and to the building and the people in it.

True or false?

At the previous r-mix company I worked at, they have 3 floating 480 Deltas. A year and a half ago one control trailer burned up at night, after what I finally found out to be a primary to secondary short. It was a sub metering setup from a primary metered mine power. When I got there the mine superintendent was flipping out because we were on the same bank as his test lab and it was winter. I thought the fire shorted the secondary drop and blew the cutouts.
Uhh no, I fused the cutouts and closed them then shut the knives at the road. All was great for about 5 seconds then the RR RRR RRRR RRRRR RRRRRR!!!!! The circulating current was taking off like mad! I barely opened the knives in time to keep the xformer from completely blowing.
I tried every way possible to explain to the owners what happened, but I couldn’t get through to them about the hazards of a floating Delta and why a corner ground is important.

 

True.

 

Works fine until a Squirrel eats through
The neutral on the Tri plex feeder from the Pole and then The occupant of the house gets a real nasty shock in the shower and they call me. The little guy was still nibbling on it when I finally traced it back, I've often wondered the hows and whys of him developing a taste for aluminium.

 

Works fine until a Squirrel eats through
The neutral on the Tri plex feeder from the Pole and then The occupant of the house gets a real nasty shock in the shower and they call me. The little guy was still nibbling on it when I finall traced it back, I've often wondered the hows and whys of him developing a taste for aluminium.

I failed to mention because I thought it would be obvious there was no grounding rod install on the service panel

 

Here is a story that illustrates how grounding can affect “operation”:


I designed, built, and installed a control system for a chair lift. The system has 12 ground rods and 45 surge arresters of various types connected to ground. Three weeks after installation lightning struck the tower at the top of the hill. The chair lift stopped operating until I replaced $2.10 worth of fuses.

About 20 years earlier and 12 miles away there was another ski hill. Its chair lift was also struck by lightning but apparently the grounding was not good. The main chair lift station burnt to ground. This triggered a bankruptcy and the hill is now “operating” as a quarry.

 

Dan at NO POINT did I say Ground Rods were not necessary for minimizing the effects of a lightning strike or a utility issue. And you are talking a grounding electrode system which is different than two rods driven 6' feet apart in soil of an unknown resistance. In addition your chair lift support poles are more than likely a better ground than just about anything you can drive into the Earth. each base is a huge Ufer Ground Electrode.

 

Are ground wires required by code?
The appliance will operate normally without the ground wire because it is not a part of the conducting path which supplies electricity to the appliance. ... The U.S. National Electric Code Article 250 requires that the ground wires be tied back to the electrical neutral at the service panel.

 

Have you read the complete thread? If you did you would know that at no point was the Equipment Grounding Conductor discussed as not necessary.

 

SparkyBB, In cases where the neutral is open aka LOST, and there is metallic water piping between residences and facilities (lets call it a unit for simplification) , the neutral current flows on the neutral ground bond in the unit that has the open neutral through the bonded metallic piping system, through the neutral ground bond in the unit that has a solid neutral and back to the source.

In a unit that has an open neutral and no metallic piping to others units with an intact neutral, ground rod or no ground rod you are going to fry some equipment.

When you have an open neutral you place the loads that were operating in parallel in series across the line conductors, depending on the impedance of the loads determines what will burn up. If the impedance is identical on each leg, you do not need the neutral. But systems are seldom to never perfectly balanced.

 

SparkyBB, In cases where the neutral is open aka LOST, and there is metallic water piping between residences and facilities (lets call it a unit for simplification) , the neutral current flows on the neutral ground bond in the unit that has the open neutral through the bonded metallic piping system, through the neutral ground bond in the unit that has a solid neutral and back to the source.

In a unit that has an open neutral and no metallic piping to others units with an intact neutral, ground rod or no ground rod you are going to fry some equipment.

When you have an open neutral you place the loads that were operating in parallel in series across the line conductors, depending on the impedance of the loads determines what will burn up. If the impedance is identical on each leg, you do not need the neutral. But systems are seldom to never perfectly balanced.

I had a building with a 120/240v service that lost its neutral in the overhead. The connected load was about 125-150 amps per phase. When the overhead neutral was losing its connection the coax TV cable that went from the building to the pole with the xfmr became the path back to the source. The coax was red hot and melting because it had 25 amps on it. The breakers in the panel were also red hot to the touch.

I’m not sure what the cable company does on the poles for grounding but it would seem they attached their splice to the GEC for the utility xfmr

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Yes, I probably should have asked that, also I think I struggle a little with "source" and electrical theory.
Thanks

 

Go to a service (single phase 120/240) BE SAFE, Clamp a conductor (if possible the service lateral or feeder in a sub-panel. Lets say you read 10 amps, clamp the other feeder simultaneously with the first and you read 4 amps. Clamp the just the neutral you should read 6 amps. Clamp all 3 conductors and you should read zero (0) amps IF NOT there is some current on your ground, check the neutral ground bond for current, check the water pipe for current, check the grounding electrode conductor at the ground rod for current. And I would bet you will have current on the other places noted but you will not have a current reading at the ground rod or if you do it is very, very low.

 

Of course, if your neutral fails and your grounding electrode conductor is connected to water pipes that are part of a city system then you will be using the neutral from neighbors' houses thru the grounding electrode conductor back to their panel. The point is, as stated many times, the ground(earth) will not conduct enough to compensate for the lost neutral.

 

In a true single phase system ground (soil) can be used as a current carrying conductor but it comes at a cost due the higher resistance. Years ago they used one wire on power poles. Higher voltages and lower amps allowed this to work.
Unfortunately we do not use a true single phase as we have 2 legs 180 degrees out of phase which leads to different results.

Anyone remember how to do the math on something like this to find the T point voltage