The Sufficiency of NEC rules

[Little Bill]

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.

You will have to show me that code. Only thing required is a bonding lug on the equipment to the bonding system. True if the case of the equipment has the EGC bonded to it, then there is a connection.
I don't know anywhere in the code, other than a pump motor that is double insulated, that says to tie directly to the building grounding system, and that is through the EGC.

 

[Sahib]

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.

The trouble with the lightning is that it can flash over from one grounding system to another if they are not bonded together. (A swimming pool bonding system with its extensive bonding grid embedded in ground (for concrete pools) is effectively grounded irrespective of it is intentionally grounded or not.) We all know too well about the hazards of power system arc flash over, for example.

 

[Sahib]

Who uses a swimming pool during a lightning storm?

People in England?

 

[Sahib]

if the case of the equipment has the EGC bonded to it, then there is a connection.

Which equipment metallic case does not require EGC connection (unless it is doubly insulated)?
None.

 

[kwired]

Who uses a swimming pool during a lightning storm?

People in England?

I was going to mention that apparently Sahib uses a swimming pool during a lightning storm.

 

[kwired]

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.

I have kind of been trying to say what don said here all along. Grounding and bonding are not the same thing. We bond everything in and around the pool to try to ensure there is no "touch potential" This bonding grid could be operating at thousands of volts above true ground, but (in a perfect world) there is no touch voltages within users reach. There likely will be current flowing through the grid, and any impedance that develops will be a weak point when it comes to developing "touch potential". The less intentional current there is in the earth the less this is a risk, which is why phase balancing of the MGN POCO distribution is somewhat important, as well as integrity of all grounded current carrying conductors - both primary and secondary sides of the POCO transformer.

When it comes to grounding, that bonding grid is generally bonded to a conductor that is grounded somewhere, which now makes the whole grid the same potential as that grounded conductor. If that grounded conductor is carrying any current there is going to be a voltage drop on it, and there will be potential between the grid and true earth. Again all the grid is really for is keeping potential between points that users can touch simultaneously at a low enough voltage it does no harm to the user.

 

[don_resqcapt19]

You will have to show me that code. Only thing required is a bonding lug on the equipment to the bonding system. True if the case of the equipment has the EGC bonded to it, then there is a connection.
I don't know anywhere in the code, other than a pump motor that is double insulated, that says to tie directly to the building grounding system, and that is through the EGC.

I said the connection would be via the EGC and in most cases that would be at the pool motor.

 

[don_resqcapt19]

The trouble with the lightning is that it can flash over from one grounding system to another if they are not bonded together. (A swimming pool bonding system with its extensive bonding grid embedded in ground (for concrete pools) is effectively grounded irrespective of it is intentionally grounded or not.) We all know too well about the hazards of power system arc flash over, for example.

If the lightning is so close as to cause a flash over, the addition of a small copper conductor between the pool bonding system and the electrical grounding system is not going to change anything.

 

[Sahib]

If the lightning is so close as to cause a flash over, the addition of a small copper conductor between the pool bonding system and the electrical grounding system is not going to change anything.

No. Many property damages and even many lives lost to lightning due to failure to bond or improper bonding.

 

[don_resqcapt19]

No. Many property damages and even many lives lost to lightning due to failure to bond or improper bonding.

I understand that, but if you are in the pool and there is a side flash to the pool bonding a connection between the grounding and bonding systems is not going to save you. While it may prevent the side flash, it will likely let enough current flow through the pool bonding sytem that there will be enough voltage drop to create a hazardous voltage gradient in the pool water.

 

[Besoeker]

People in England?

The English might, I suppose.....

 

[kwired]

No. Many property damages and even many lives lost to lightning due to failure to bond or improper bonding.

There has been many incidents where lightning caused damage even when proper bonding was done.

Bonding throughout the electrical system is generally not done specifically for lightning purposes.

 

[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.

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, I think we are on the same page, but the statements in red made it sound like (to me) that you were saying the code was requiring a dedicated direct connection to the grounding system of the building. I was basing my replies on 680.26(B):

680.26 Equipotential Bonding.

(B) Bonded Parts. The parts specified in 680.26(B)(1)
through (B)(7) shall be bonded together using solid copper
conductors, insulated covered, or bare, not smaller than
8 AWG or with rigid metal conduit of brass or other identified
corrosion-resistant metal. Connections to bonded
parts shall be made in accordance with 250.8. An 8 AWG or
larger solid copper bonding conductor provided to reduce
voltage gradients in the pool area shall not be required to be
extended or attached to remote panelboards, service equipment,
or electrodes.

 

[don_resqcapt19]

Don, I think we are on the same page, but the statements in red made it sound like (to me) that you were saying the code was requiring a dedicated direct connection to the grounding system of the building. I was basing my replies on 680.26(B):

680.26 Equipotential Bonding.

(B) Bonded Parts. The parts specified in 680.26(B)(1)
through (B)(7) shall be bonded together using solid copper
conductors, insulated covered, or bare, not smaller than
8 AWG or with rigid metal conduit of brass or other identified
corrosion-resistant metal. Connections to bonded
parts shall be made in accordance with 250.8. An 8 AWG or
larger solid copper bonding conductor provided to reduce
voltage gradients in the pool area shall not be required to be
extended or attached to remote panelboards, service equipment,
or electrodes.

There is not an extension of the #8 bonding conductor back to the electrical system. but it would be a very rare installation where the code did not require a physical connection between the pool bonding system and the EGC for the pool equipment.

 

[kwired]

There is not an extension of the #8 bonding conductor back to the electrical system. but it would be a very rare installation where the code did not require a physical connection between the pool bonding system and the EGC for the pool equipment.

Like a pool with no electrical equipment. Maybe they have gas powered circulating pumps?

 

[Sahib]

There has been many incidents where lightning caused damage even when proper bonding was done.

A conventional lightning protection system with proper bonding allows bypasses, but that would not cause any damage per design. But if what you say were true, it means failure of conventional lightning protection system. So if you provide details about it, I could proudly present it to Yahoo lightning protection group based on conventional lightning protection and run by lightning protection professionals

Bonding throughout the electrical system is generally not done specifically for lightning purposes.

Bonding for protection against power system fault potentials may well afford protection against lightning as the lightning current follows diverse paths and exists for much shorter duration.

 

[kwired]

I agree that lightning protection systems minimize potential damage, and even proper equipment grounding can possibly reduce damages during a lightning event.

You will not convince me that it is possible to design a lightning protection system that is "bullet proof".

 

[Sahib]

"bullet proof".

I never implied it, because conventional lightning protection is based on statistical thinking. So it will be highly interesting if you bring out lightning damages in a system designed with conventional lightning protection as it is a very rare event.

 

[iwire]

Almost 60 posts in and the OP still has not pointed out any particular NEC section that is inadequate or provided any solutions for inadequate NEC sections. I guess he does not really want to talk about the NEC or making it better.

 

[Sahib]

Thanks, iwire for your reminder.

But my stand throughout the thread, I would like to bring to your kind notice, is that NEC rules are sufficient to afford protection in any situation. I am, with other members are discussing, to find out any shortcomings in the rules.

Would you like to join with us?