Almost understanding grounding and bonding

[William J. Decker]

OK, you ol' hillbilly, ya got me.

Impedance is the resistance of a component at a given frequency.

New paradigm.

M.S. in Physics - Consider the Universe.

Master Sparky - Do the freakin' job (and get paid).

I, humbly, stand corrected.

Now, Paul, give us a kiss.

[Mike Whitt]

Originally Posted by Greg Fretwell

680.23(B)(2) does not relieve the installer from bonding the niche to the listed light J box, even if it is low voltage. 680.23(F)(2) extends that to the panel with an insulated #12.

Originally Posted by Greg Fretwell

I suppose we can come up with a scenario where the pool is not bonded to the service but it would be rare. Usually you have several paths.

(B) Wet-Niche Luminaires (Fixtures).
(1) Forming Shells. Forming shells shall be installed for the mounting of all wet-niche underwater luminaires (fixtures) and shall be equipped with provisions for conduit entries. Metal parts of the luminaire (fixture) and forming shell in contact with the pool water shall be of brass or other approved corrosion-resistant metal. All forming shells used with nonmetallic conduit systems, other than those that are part of a listed low-voltage lighting system not requiring grounding, shall include provisions for terminating an 8 AWG copper conductor.
(2) Wiring Extending Directly to the Forming Shell. Conduit shall be installed from the forming shell to a junction box or other enclosure conforming to the requirements in 680.24. Conduit shall be rigid metal, intermediate metal, liquidtight flexible nonmetallic, or rigid nonmetallic.
(a) Metal Conduit. Metal conduit shall be approved and shall be of brass or other approved corrosion-resistant metal.
(b) Nonmetallic Conduit. Where a nonmetallic conduit is used, an 8 AWG insulated solid or stranded copper bonding jumper shall be installed in this conduit unless a listed low-voltage lighting system not requiring grounding is used. The bonding jumper shall be terminated in the forming shell, junction box or transformer enclosure, or ground-fault circuit-interrupter enclosure. The termination of the 8 AWG bonding jumper in the forming shell shall be covered with, or encapsulated in, a listed potting compound to protect the connection from the possible deteriorating effect of pool water to protect the connection from the possible deteriorating effect of pool water.

Although you have pointed out one of the three different niche type of lights that can be installed in a pool, the other two being dry niche and no niche, the use of a #8 conductor between two nonmetallic components wound not be bonded to the equipment grounding conductor.

The use of fiber optic lights which is growing by leaps and bounds in my area of the nation will have no physical connection to the bonding grid. Most of the low voltage lights I have encountered over the past several years don’t have a connection to the bonding grid either.

I have seem several pool installations in the past couple of years where the bonding grid had no connection to the equipment grounding conductor at all.

[Greg Fretwell]

Personally I see that as less safe. You are basically saying there is no real connection to the bonding grid and it may be significantly above the potential of that Bell box the 2008 has now let you put 5' from the water and 2' from the bonded pool deck. If you have some stray voltage that elevates the potential of the pool above the "ground" of the service, anything with an exposed bonded metal case or any wiring method will impose that difference on a person sitting on that deck.

[Paul W. Abernathy]

lol......no problem William.....lol...Hillbilly...lol....I love it

[Mike Whitt]

Originally Posted by Greg Fretwell

Personally I see that as less safe. You are basically saying there is no real connection to the bonding grid and it may be significantly above the potential of that Bell box the 2008 has now let you put 5' from the water and 2' from the bonded pool deck.

I am confused about what you are saying here. There are two things in this statement that has me confused and I will address the last half of this statement first.
The 2008 cycle of the NEC in 680.22(A)(1) has moved the minimum distance of a receptacle for a pool out to a distance of six feet not moved it in to a less distance. Where are you getting the information that the distance is less?
In the first part of this statement you ask if I am saying that the equipotential bonding grid is not to be connected to the grounding electrode system of the service.
This is exactly what I am saying.
Because of the debate over the connection of the equipotential bonding grid to the service grounding electrode system the Fine Print Note found under 680.26(A) of the 2005 code was incorporated into the language of 680.26(B) of the 2008 code.
Let’s also not forget that any metal within five feet of the inside wall of a pool must be bonded to the equipotential bonding grid as outlined in 680.26(B)(5).

Originally Posted by Greg Fretwell

“2' from the bonded pool deck.” If you have some stray voltage that elevates the potential of the pool above the "ground" of the service, anything with an exposed bonded metal case or any wiring method will impose that difference on a person sitting on that deck.

I brought the “2' from the bonded pool deck.” Down to this as I think that there might be some confusion about just what the equipotential bonding grid is to accomplish.
The purpose of the equipotential bonding grid is not to remove any voltage that is present. The purpose is to eliminate voltage gradients in the pool area as prescribed.
This was cleared up just a little in the 2008 cycle by changing the word “eliminate” to “reduce”.
It is not the purpose of the equipotential bonding grid to protect the person that is sitting on the deck but to protect the person that is in the water from getting a shock that would influence their ability to retreat from the water.
My back yard is fenced in from one corner of the house to the other corner of the house. Anyone walking around in the back yard that might touch the fence might get a shock from stray voltage that elevates the potential of the fence above the "ground" of the service, Am I to install a conductor from the fence to the electrode system of my service to prevent this from happening?
The same answer is the answer to your question above.

Remember that we are protecting the “pool area” not anything more. The “pool area” is that area starting 3 feet outside the body of water extending across the body of water to a distance of three feet outside the body of water.
We could keep doing the “what ifs” until we reach from the Atlantic to the Pacific trying to end the affects of the “stray voltages” outside the pool area but the code clearly states the area involved.

[Greg Fretwell]

Mike you brought up the "what ifs" when you talked about a pool with no grounded equipment to bond. You are right, I mis spoke it is 6' on the receptacle but switching devices are still >5' and that can still be in a metal bell box.
You are also the one who brought up the idea that the EGC to that bell box might be significantly above ground because of a fault in the neutral.
BTW, now that we are required to bond the deck the "pool area" is the whole deck, that concrete doesn't know to stop conducting at 3'.

OK your "what if"

Fault in the neutral, EGC is 20v above ground, bell box 62" from the water is 20v above ground. Pool is still at ground because there is no connecton to the EGC and it is a 2000 sq/ft Ufer. I am sitting on the wet pool deck (bonded to the pool) and I touch the switch box.
How many volts will I have across my body?

See what I mean, Not bonding to the EGC is less safe. You have created the gradient you are trying to eliminate and you demonstrated it with your example.

The reality of a pool with no EGC to pool bond connection is fairly new since
there wern't any fiber lights, double insulated pumps and such out there. Red brass was the most common method to pipe an underwater light for many years. The idea that the EGC was supposed to be separate from the 680.26 grid was just a theory that could seldom actually be achieved. I predict that if this becomes common we will start seeing people get shocked, maybe to death.

[Mike Whitt]

Originally Posted by Greg Fretwell

Mike you brought up the "what ifs" when you talked about a pool with no grounded equipment to bond.

You are right I did use “what if” first but it was in response to the Bell box and the person sitting on the deck. To me that is a “what if” that the code does not address.

Originally Posted by Greg Fretwell

You are right, I mis spoke it is 6' on the receptacle but switching devices are still >5' and that can still be in a metal bell box.

Originally Posted by Greg Fretwell

You are also the one who brought up the idea that the EGC to that bell box might be significantly above ground because of a fault in the neutral.
BTW, not that we are required to bond the deck the "pool area" is the whole deck, that concrete doesn't know to stop conducting at 3'.

Watch for that to change in 2011 and if accepted it will be any wiring device to not be within 6 feet.
Not sure what you are saying in the second half because we are required to bond the deck. If there is nothing in that deck to bond to then the electrician is required to install one that is described in 680.26(C).
You have also brought up a good point that a deck could possibly be 10 foot wide. The codes only address the first 3 feet of that deck. This is the distance that the average person can reach outside the pool while in the water.

Originally Posted by Greg Fretwell

OK your "what if"

Originally Posted by Greg Fretwell

Fault in the neutral, EGC is 20v above ground, bell box 62" from the water is 20v above ground. Pool is still at ground because there is no connecton to the EGC and it is a 2000 sq/ft Ufer. I am sitting on the wet pool deck (bonded to the pool) and I touch the switch box.
How many volts will I have across my body?

A quick answer would be 20 volts but the technical answer would have many variables.
Now can I ask you if you can reach that box while in the water?
Article 680 is protecting the people that is in the water not those walking around above ground.
But to address the Bell box that is within 62 inches of the pool I believe that 680.26(B)(5) will cover this installation.

Originally Posted by Greg Fretwell

See what I mean, Not bonding to the EGC is less safe. You have created the gradient you are trying to eliminate and you demonstrated it with your example.

Again you are addressing those that are above ground instead of someone in the water.
In you scenario you have focused on a concrete pool. Many pools are fiberglass body pools.
Now if I am in a fiberglass pool and the equipotential bonding grid is bonded to that same switch as I am exiting the fiberglass pool the second I touch the deck I will be at a different potential while still in the water. This is what we want to prevent is it not?
If all pools were as the one you have described I would see no problem but the simple truth is not all pools are as the one you described.
There was a proposal in the past couple of code cycles to bond the water in the pool that was accepted in the 2008 cycle. 680.26 was rewritten and in subsection (C) we find this requirement to have no less than nine square inches of conductive surface in contact with the water and this conductive surface if to be bonded to the equipotential bonding grid.
A reading of the Report on Proposals for Article 680 will render a different understanding on just what is to be accomplished with the equipotential bonding grid.

Originally Posted by Greg Fretwell

The reality of a pool with no EGC to pool bond connection is fairly new since there wern't any fiber lights, double insulated pumps and such out there. Red brass was the most common method to pipe an underwater light for many years. The idea that the EGC was supposed to be separate from the 680.26 grid was just a theory that could seldom actually be achieved. I predict that if this becomes common we will start seeing people get shocked, maybe to death.

In my area the use of fiberglass lined pools has been the norm for dwellings for the past several years. When I make a pool installation I always use nonmetallic raceways and enclosures just for the safety factor. I will bend over backwards to keep the equipotential bonding grid away from any equipment grounding conductor on a fiberglass pool.
Some of the pools that I have installed didn’t have ladder or handrail nor was a light installed so nothing was being bonded that was in contact with the water. This type of installation is one of the cheapest that money can buy and are just a step above an above ground pool.
This type of pool is what the new 680.26(C) was written for. I understand that someone that has never had any dealings with these cheap pools could get accustom to inspecting concrete pools without any regard to the giant capacitor that the above described pool has formed.
It would be the use of this type of pool that I would be worried about instead of a concrete pool. It is also the type of pool that is referenced most in the ROPs.

[Greg Fretwell]

Ref 680.26(B)(5), 62" is 5' 2"

The point is still that the equipotential grid is supposed to protect people in and around the pool. The water is supposed to be bonded to the grid via the equipment, it is only the same modern "improvements" that have created this hazard.
When we started requiring that the deck was part of the grid we extended that danger to the edge of the deck. When you say electrical equipment around the pool is not supposed to be part of that equipotential grid and the grid is not connected to the EGC all you have done is move the "kill zone" out a couple feet.
Bear in mind this doesn't have to be the wiring method that gets energized by your neutral fault, it could also be the case of cord and plug connected equipment with a grounded plug.
I still say the "ground plane" for the service should be bonded to the ground plane of most dangerous places we use electricity. That is why we bond plumbing.
I do believe there will be more emphisis on bonding the water and pretty soon we will be back to using bonded equipment or providing a bonding electrode in the water.
... but we will have to kill a few people first.