The Sufficiency of NEC rules

[cowboyjwc]

I am still confused at where you have this continuity. If you are looking at the neutral on the load side of the service neutral disconnect, then I don't see how anything at the utility side would make any difference.

If you are looking at the utility side of the neutral, then you will have a path via the service grounding electrode and the utility grounding electrode. In many cases this will not be a low impedance path, but there are a number of conditions that are normal and would create a low impedance path.

And that's why I said that I think I may have made a mistake by not making them pull the disconnect link. I don't think that they were completely isolated like they should have been.

Because of the low impedance path, you don't use a top of the line tester. Just one of the flashlight types is fine. The good digitals will usually not zero out.

 

[Sahib]

The dairy barn wired to NEC minimum does not have near the detailed bonding requirements as a swimming pool.

You mean a barn is less safe than a swimming pool even when both are code compliant?

When it comes to maintenance, every dairy barn always has fully qualified and high knowledge maintenance electricians on staff 24/7:happyno:

In many cases, the electricians get shocked or even electrocuted, despite fully qualified and high knowledge. :happysad:

 

[kwired]

You mean a barn is less safe than a swimming pool even when both are code compliant?

possibly yes. there are similar conditions in each, and there are differences in each. They do not have the same requirements either

In many cases, the electricians get shocked or even electrocuted, despite fully qualified and high knowledge. :happysad:

yes they do, and in more places than just swimming pools or dairy barns. You responded to a sarcastic reply, read it a little harder, no reply was expected other than maybe a joke.

 

[Sahib]

. there are similar conditions in each, and there are differences in each. They do not have the same requirements either

Perhaps like comparing apples to oranges.

yes they do, and in more places than just swimming pools or dairy barns. You responded to a sarcastic reply, read it a little harder, no reply was expected other than maybe a joke.

Mine was also similar, for professional overconfidence is mainly the cause of electrical accidents involving animals and electricians and not a lack of sufficiency of NEC rules to cause the same.

 

[meternerd]

The POCO neutral is multi-grounded. So the ground return current can be substantial. This can give rise to touch and step voltage issues, which are serious as regards swimming pools and cattle farms. But the NEC grounding and bonding rules should be sufficient to solve these issues and where they lack, the rules might have been amended long back to afford increased effectiveness. But still do such rules of the NEC lack in any important aspect of protection? Your inputs please.

I didn't read all of the posts, but here's my 2 cents. Utilities use 4 wire grounded neutrals with multiple grounds because we want to be able to clear a ground fault within the shortest time possible. Faults flow from phase to neutral because that's how it's wired at the substation. The substation neutral is grounded, but if the system neutral should become compromised, then fault current will have to return through the earth until it finds an intact neutral. If the ground return path back to the nearest protective device is fairly high impedance, a downed phase could lay on the ground undetected for quite a while. If some unsuspecting soul should touch it, they could become a parallel path and be a victim. Not good. Remember that distribution is mainly overhead, and earth resistance can be pretty high. If a ground doesn't trip a breaker or blow a fuse, it's a HUGE danger. Agreed that stray current exists, but it is often due to poorly maintained systems, where pole grounds have been broken or stolen. I have trouble thinking of systems where the earth is intentionally used as the return path. Maybe I need to widen my horizons.

 

[kwired]

Mine was also similar, for professional overconfidence is mainly the cause of electrical accidents involving animals and electricians and not a lack of sufficiency of NEC rules to cause the same.

Which gets us back to what the sarcastic comment was all about. Once the initial installation is finished, who is there that knows enough to maintain it? The users certainly don't complain as long as machines and lights are doing what is intended. Something has to happen before an expert is called in to see what is going on. Anything that can be done to minimize the risk of stray currents in the original design, especially things like minimizing use of grounded conductor usage, will help prevent stray currents from even having much chance of even happening.

 

[Sahib]

This issue is the reason that the NEC added the perimeter surface bonding rule for pool decks.

And still there should not be any connection between building metal and that of the pool. Isn't it?

 

[don_resqcapt19]

And still there should not be any connection between building metal and that of the pool. Isn't it?

The pool bonding grid will have a connection to the building electrical grounding system and therefore to any metal that is connected to the building electrical grounding system. In addition, any fixed metal parts that are within 5' horizontally of inside of the pool wall are required to be connected to the pool bonding system.

 

[Sahib]

The pool bonding grid will have a connection to the building electrical grounding system and therefore to any metal that is connected to the building electrical grounding system.

Thanks, Don for your reply.
My point is if there is a danger of a metallic part of a building not forming part of the electrical installation becomes live due to damage to a cable and if there is any inadvertent connection between it and that of the pool, this could cause electrocution of pool users besides building users. So such connections must be searched and weeded out.

 

[kwired]

Thanks, Don for your reply.
My point is if there is a danger of a metallic part of a building not forming part of the electrical installation becomes live due to damage to a cable and if there is any inadvertent connection between it and that of the pool, this could cause electrocution of pool users besides building users. So such connections must be searched and weeded out.

And building occupants (most of which are not electrical professionals) are always on a constant lookout for this very thing:slaphead:

 

[Sahib]

And building occupants (most of which are not electrical professionals) are always on a constant lookout for this very thing:slaphead:

Again sarcastic?

My point in post # 29 is aimed towards the thread title: Are the code rules sufficient to make such a search unnecessary?

 

[Little Bill]

The pool bonding grid will have a connection to the building electrical grounding system and therefore to any metal that is connected to the building electrical grounding system. In addition, any fixed metal parts that are within 5' horizontally of inside of the pool wall are required to be connected to the pool bonding system.

There is no requirement for a pool bonding grid to be run to the building grounding system.
It might be connected inadvertently through EGCs, but not directly from one to the other unless someone decided to do that.

 

[Sahib]

There is no requirement for a pool bonding grid to be run to the building grounding system.
It might be connected inadvertently through EGCs, but not directly from one to the other unless someone decided to do that.

Pool bonding alone is not sufficient. It must be grounded to 'drain' any stray voltages. But no two separate grounds.

 

[iwire]

Pool bonding alone is not sufficient. It must be grounded to 'drain' any stray voltages.

It must be grounded to do what?

 

[Sahib]

It must be grounded to do what?

To equalize the pool bonding potential due to any stray voltages with the ground potential.

 

[don_resqcapt19]

To equalize the pool bonding potential due to any stray voltages with the ground potential.

As long as everything within the pool area is bonded, we don't really need a connection to the electrical grounding system to make it safe. Unless there is an excessive amount of current the voltage on everything connected to the pool bonding system will be the same voltage and. If there is excessive current, a connection to the electrical grounding system will not really make an difference.
The very source of the "stray voltage" at the pool is often a result of the code rule that requires a connection between the pool bonding system and the electrical system. The code is requiring us to energize the pool bonding system.

 

[don_resqcapt19]

There is no requirement for a pool bonding grid to be run to the building grounding system.
It might be connected inadvertently through EGCs, but not directly from one to the other unless someone decided to do that.

If the pool has any electrcial equipment, then the code requires a connection between the EGC and the pool bonding system. That is a "direct" connection to the electrical grounding system, in my opinion.

 

[Sahib]

As long as everything within the pool area is bonded, we don't really need a connection to the electrical grounding system to make it safe. Unless there is an excessive amount of current the voltage on everything connected to the pool bonding system will be the same voltage and. If there is excessive current, a connection to the electrical grounding system will not really make an difference.
The very source of the "stray voltage" at the pool is often a result of the code rule that requires a connection between the pool bonding system and the electrical system. The code is requiring us to energize the pool bonding system.

On the contrary, protection from lightning requires single point grounding.

 

[don_resqcapt19]

On the contrary, protection from lightning requires single point grounding.

I really doubt that the bonding jumper between the pool bonding system and the electrical grounding system would make any difference in the case of a nearby lightning strike. There will be enough current that there will be a hazardous voltage drop on the bonding and grounding system. If there is not enough current to create that hazardous voltage drop, then the bonding grid will still do its job....everything connected is as the same voltage.

 

[Besoeker]

On the contrary, protection from lightning requires single point grounding.

Who uses a swimming pool during a lightning storm?