More fun with pool bonding

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Podagrower

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Central Fl
So Florida has adopted the equipotential bonding grid section of the 08 NEC. I have done two pool since the change (they are not my specialty).

My question is this. We bond all the parts-rebar, ladders, handrails, pumps, water- to eliminate stray voltages. If this grid has a lower resistance to ground than our building ground system, aren't we creating a hazard by making the pool a ground source?

The first pool I did after the change was a commercial install. Building ground system was 3x20' 3/4 ground rods (triangle), Ufer ground, cold water (2" copper 20' long). At the time, I had acces to an Ideal ground resistance meter, and boredom to kill. I don't remember the exact numbers, but in the MDP, the ground wire going to the pool panel had lower resistance to ground than the building ground system (the pool has a deck box for a water powered handicap lift that is connected to a lot of copper pipe fed from the water meter, not the building). As I said, I don't remember the numbers, and it wasn't a huge difference, but I don't think using the pool for a ground is what the writers intended.

What say you?
 
Podagrower said:
So Florida has adopted the equipotential bonding grid section of the 08 NEC. I have done two pool since the change (they are not my specialty).

My question is this. We bond all the parts-rebar, ladders, handrails, pumps, water- to eliminate stray voltages. If this grid has a lower resistance to ground than our building ground system, aren't we creating a hazard by making the pool a ground source?
Click to expand...

I generally don't recommend swimming when its lightning outside.
 
Podagrower said:
My question is this. We bond all the parts-rebar, ladders, handrails, pumps, water- to eliminate stray voltages.
Click to expand...
No, we do it to equalize the voltage among all the components. If they were all energized to, say, 50 volts, then there would be no potential between them, so you could touch any two components and not feel any voltage. That's it's purpose.

It actually hurts us in the stray voltage department, because neutral current will also travel along that path, both secondary and primary of the utility.

If this grid has a lower resistance to ground than our building ground system, aren't we creating a hazard by making the pool a ground source?
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Conceivably, and stray voltage has been the focus of many proposals to undo the equipotential bonding requirements. Such attempts have soundly failed up to now.
 
Chris,

Florida Senate Bill 2836 was signed into law last summer. This bill allowed the option of using 680.26 of the 2008 NEC in lieu of 680.26 of the 2005 NEC. The Florida Building Commission was then mandated to place the rule into the FBC at the next glitch cycle or code update. Since the 2008 will NOT be adopted with the 2007 FBC on March 31, 2009; 680.26 will be located in Chapter 27 of the 2007 FBC with the 2007 Glitch.

By the way, the Florida Building Commission meets next week to decide on the 2008 NEC adoption date. I will be present at the meeting and will update the members of this forum.
 
The problem is not all of the bonding between all those parts in and around the pool. . The problem arises because of the bonding conductor that leaves the pool area and runs over to hook onto a lug on the pool motor. . The pool motor has an equipment ground that is electrically continuous to the service and bonded to the service neutral.

A bad connection on the service neutral, either at the service/main disconnect or at the supplying transformer could cause a significant amount of the current, from loads supplied by that service, to find an alternative return path to the supplying transformer. . That huge amount of earth contact at the pool grid can give a lower impedance path than other options.

When the pool motor is not next to the pool, the bonding wire from grid to pool motor has more potential to cause harm than potential to cause good/add safety. . But the NEC doesn't recognize that reality.

Some western states recognize this same type of problem in 547 and exempt compliance with the first sentence of 547.10(B).
 
Another concern is the bonding wire is not prohibited from being attached to the panel-board enclosure ,..and many are.

This is a good little read,..

Link
 
M. D. said:
Another concern is the bonding wire is not prohibited from being attached to the panel-board enclosure ,..and many are.
Click to expand...

The bond to the motor casing creates the same connection as bonding directly to the panel board enclosure. . There is a direct connection between the transformer and the pool grid either way.

I would never tell a contractor or homeowner to do something that is against the NEC, but I will tell you that my pool motor does not have a bonding wire from the pool on the motor case lug. . It no longer has a lug at all. . It has an equipment ground attached to the motor case internally that runs back to the panel and that's the way it's going to stay.
 
David,

I completely follow your line of thought. What is missing is any evidence of this being a problem. Florida has millions of pools. There are simply not many reported cases out there that have conclusively led to the pool acting as a concrete-encased electrode and resulting in an injury or death.

Logic and theory tells us normally operating currents will likely be present on the pool parts, but it doesn't seem to be a problem.

Most cases of "tingle voltage" at pools as has been a result of stray utility currents and NOT those originating from the premise wiring.

Its a real mystery...
 
bphgravity said:
Chris,

Florida Senate Bill 2836 was signed into law last summer. This bill allowed the option of using 680.26 of the 2008 NEC in lieu of 680.26 of the 2005 NEC. The Florida Building Commission was then mandated to place the rule into the FBC at the next glitch cycle or code update. Since the 2008 will NOT be adopted with the 2007 FBC on March 31, 2009; 680.26 will be located in Chapter 27 of the 2007 FBC with the 2007 Glitch.

By the way, the Florida Building Commission meets next week to decide on the 2008 NEC adoption date. I will be present at the meeting and will update the members of this forum.
Click to expand...
Thanks for the info Bryan. I'll be looking for your update.
 
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