ground rod for remote panel at swimming pool

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Re: ground rod for remote panel at swimming pool

Wayne
Sometimes examples are the best teacher.

Let him stand next to the groundrod. Impose a voltage to the groundrod, and then he can take a 3 foot step (barefoot of course).....Ouch! That would be a lesson of step potential that most would not forget. :D
 
Re: ground rod for remote panel at swimming pool

Here's a story to illustrate my confusion.

Once upon a time there was an apprentice who just didn't get it. One time, he and the j-man on the job were laying out parallel URD runs to power an 800 amp service. They were probably 50 feet long, so once the runs were laid out, the journeyman (let's call him Connor) took out his multimeter and told the apprentice (let's call him Andy) to touch a phase to neutral, and whichever phase toned out would be the red.

Well, Andy misunderstood Connor, and marked the wrong phase red. This mistake went unnoticed until the POCO decided to energize the disconnect, which resulted in quite a display.

According to a framer that was standing in the finished building next door, standing barefoot on a slab, washing his hands in the kitchen sink before lunch, he got a really good jolt. Now, at the time I figured he was lying to get attention (or free beer, he made mention of free beer on more than one occasion).

But knowing now what I know (i.e. electricity seeks any path back to it's source) it makes the framer's story is somewhat more believable.

Now, if the neutral were not connected to the structure's grounding electrodes the framer would have felt no jolt.

So, is grounding doing it's job?
 
Re: ground rod for remote panel at swimming pool

Andy, are you saying the building grounding system became energized?

And we all want free beer, whether we conciously realize it or not. :D
 
Re: ground rod for remote panel at swimming pool

George
If a ungrounded conductor was connected to the neutral between the transformer and the service disconnect only one thing would happen (this is without a commonly bonded water pipe) All grounding would be at 120 volt potential to Earth. A ground rod would not do anything but add a small 4.8 amp load to the service.

This is one of the main mis-conceptions that Mike Holt was trying to get accross everyone when he was disputting people installing ground rods for lighting standards. The ground rod does not serve any purpose of removing a fault. And even at the higher voltage of the primary's the one at the service can fault the POCO's OCPD but requiring a ground rod after the service does not serve any purpose to safty on non-habitable structures. IE. post holding receptacles or a load center. If the voltage was able to maintain from the first grounding electrod system at the service what do they think the second ground rod will do with more impedance in the path?

It is a requirment that serves no purpose!
 
Re: ground rod for remote panel at swimming pool

installing ground rods for lighting standards. The ground rod does not serve any purpose of removing a fault.
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Are you talking about municipal light standards Wayne?
 
Re: ground rod for remote panel at swimming pool

Don't ground rods clear primary faults? Sometimes.
 
Re: ground rod for remote panel at swimming pool

Originally posted by hurk27:
If a ungrounded conductor was connected to the neutral between the transformer and the service disconnect only one thing would happen (this is without a commonly bonded water pipe)
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These buildings both had completed services, with water bonds. I assume that the two building's supply were connected.

Another interesting bit: The mistake was phase-to-phase, a bolted fault. The black was directly connected to the red in parallel. In theory, the neutral shouldn't have become energized, would it? :confused:
 
Re: ground rod for remote panel at swimming pool

By George: The mistake was phase-to-phase, a bolted fault. The black was directly connected to the red in parallel.
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You are correct a line to line fault is just that. It could not have imposed any voltage on the neutral or grounding, unless the primary neutral has some resistance loss ahead of the transformer to allow it to have a little voltage drop that caused voltage to be on the buildings Grounding system. I have seen where a lost primary neutral ahead of the common connection with the secondary neutral did cause a voltage to appear on all the grounding of a apartment building. But it is a rare case when this happens, as most of the time the water pipes will keep the voltage to a point where it is un-noticeable. But this apartment building had plastic pipes to the street. Which the water company installed because they kept having leaks in the copper pipes. which was caused by the loss neutral in the first place. :roll:

[ May 30, 2005, 01:32 AM: Message edited by: hurk27 ]
 
Re: ground rod for remote panel at swimming pool

The grounding electrodes located at the second panel serves to reduce the potential difference that can occur when there is a ground fault and a person might be in contact with the equipment while standing on the ground. In order to reduce the likelihood of a potential difference, you should establish a ground plane for equipment as close as possile to area where personnel might come in contact with it.
 
Re: ground rod for remote panel at swimming pool

But John, that's not currently required by the NEC. And creating an equipotential bonding grid for 400' around and inside a building is a little excessive, don't you think? :D
 
Re: ground rod for remote panel at swimming pool

Perhaps it isn't the intention of the code but I do agree with John that "putting" the earth at no voltage is a good idea with respect to at least attempting to keep people from becoming energized.
 
Re: ground rod for remote panel at swimming pool

John,
The grounding electrodes located at the second panel serves to reduce the potential difference that can occur when there is a ground fault and a person might be in contact with the equipment while standing on the ground.
Click to expand...
Unfortunately it just doesn't work very well for that purpose. Most of the voltage drop around a grounding electrode is within the first 30" or so of the electrode, beyond that point there is no reduction in potential.
Don
 
Re: ground rod for remote panel at swimming pool

By John: The grounding electrodes located at the second panel serves to reduce the potential difference that can occur when there is a ground fault and a person might be in contact with the equipment while standing on the ground. In order to reduce the likelihood of a potential difference, you should establish a ground plane for equipment as close as possile to area where personnel might come in contact with it .
Click to expand...
Maybe we should carry a ground rod around and drive it in where ever we use power tools? :(
 
Re: ground rod for remote panel at swimming pool

So, what's the verdict? Is someone wanting to try to beat grounding into my head? I'm hoping somebody will step up... :)

I just can't understand why grounding protects against line surges.

If a structure cut it's losses when accidental contact with overhead lines occurred, it seems that the POCO would take care of itself, and Freddy taking a bath wouldn't get a free vasectomy. :D
 
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