Equal potential/pools
- Thread starter pridelion
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hey_poolboy
Senior Member
- Location
- Illinois
Re: Equal potential/pools
pridelion,
as for procedure see art. 680
If it is new construction, try to lead the builder toward fiber optic lighting. Plastic housing, and no power poolside. (fiberstars makes good stuff)
Resistance limits I would infer should be the same as required for the house. In 250 it mentions 25 Ohms to between ground rod and ground.
But I'm not sure on that one.
pridelion,
as for procedure see art. 680
If it is new construction, try to lead the builder toward fiber optic lighting. Plastic housing, and no power poolside. (fiberstars makes good stuff)
Resistance limits I would infer should be the same as required for the house. In 250 it mentions 25 Ohms to between ground rod and ground.
But I'm not sure on that one.
bphgravity
Senior Member
- Location
- Florida
Re: Equal potential/pools
Performance bonding is a completely different issue than service grounding. Resistance is not of any real consideration when making equipotential bonds. In order to stop two points of a conductive surface from having different potentials in which current can flow, bonding can be performed to place all surfaces and components at an equal potential. Resistance will not play too much of a part.
This is also achieved when we ground a service, however, the low resistance needed at a service is for lighting and high-voltage cross-over events.
Performance bonding is a completely different issue than service grounding. Resistance is not of any real consideration when making equipotential bonds. In order to stop two points of a conductive surface from having different potentials in which current can flow, bonding can be performed to place all surfaces and components at an equal potential. Resistance will not play too much of a part.
This is also achieved when we ground a service, however, the low resistance needed at a service is for lighting and high-voltage cross-over events.
hey_poolboy
Senior Member
- Location
- Illinois
Re: Equal potential/pools
Brian,
I see what you mean and I understand the equal potential situation. With the new bonding requirements in art. 680 it seems as if they are trying to head towards a lower resistance to ground. Puting the copper grid under a non-conductive pool surface didn't make much sense to me until I read your post, then it clicked.
I'm a little slow sometimes.
As the person exits an insulated pool (fiberglass) and steps onto the deck they are going to grab the handrail which could be at a different potential than the water even if bonded properly. By adding the copper grid under the pool (680.26) the attempt is to give the bonding grid a lower resistance to ground than the human.
Is that correct?
Brian,
I see what you mean and I understand the equal potential situation. With the new bonding requirements in art. 680 it seems as if they are trying to head towards a lower resistance to ground. Puting the copper grid under a non-conductive pool surface didn't make much sense to me until I read your post, then it clicked.
I'm a little slow sometimes.
As the person exits an insulated pool (fiberglass) and steps onto the deck they are going to grab the handrail which could be at a different potential than the water even if bonded properly. By adding the copper grid under the pool (680.26) the attempt is to give the bonding grid a lower resistance to ground than the human.
Is that correct?
- Location
- Illinois
- Occupation
- retired electrician
Re: Equal potential/pools
Don
No. The attempt is to keep everything within step or touch at the same potential. The resistance to earth is not important. If there is voltage flowing in the earth, there may be dangerous voltages between things that are within step or touch
Don
Re: Equal potential/pools
Poolboy, as Don points out,
Picture a pool on a structure 100' above ground with complete isolation from ground, there would still be a need to bond the surfaces but grounding plays no part in it.
However, the physical connections would need to be at a low reading if measured in a loop with a ohm meter.
Roger
Poolboy, as Don points out,
This would not necessarily be zero. If we bonded all the items together and energized all at 120v (just for conversation) on them, it would still be safe since all would be equal.
Picture a pool on a structure 100' above ground with complete isolation from ground, there would still be a need to bond the surfaces but grounding plays no part in it.
However, the physical connections would need to be at a low reading if measured in a loop with a ohm meter.
Roger
hey_poolboy
Senior Member
- Location
- Illinois
Re: Equal potential/pools
I guess what I'm confused about what it is that is being accomplished with this copper grid. All things being equal. If you are exiting a pool that is a natural insulator (fiberglass) What difference does this grid in the ground under the pool make. If everything were bonded according to 2002 code (without the copper grid under the actual pool shell)What difference is there. The grid will still not bond the water of a non-conductive shell to the rest of the bonding grid.
I guess what I'm confused about what it is that is being accomplished with this copper grid. All things being equal. If you are exiting a pool that is a natural insulator (fiberglass) What difference does this grid in the ground under the pool make. If everything were bonded according to 2002 code (without the copper grid under the actual pool shell)What difference is there. The grid will still not bond the water of a non-conductive shell to the rest of the bonding grid.
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: Equal potential/pools
Poolboy: Think of it this way:
Everything that is connected to the electrical service has about 1-4 volts on it. That is because the utility is using the earth a parallel path for nuetral current. So, the pool motor gets connected to the service equipment because it has to. We then might have 1-4 volts in the water. By bonding the pool steel to the ladder and the deck and everything else, we are basically intentionaly energizing them! We are trying to put voltage on these metal parts! The reason for this is to make the swimmer just like the bird on a wire...everything you touch is 3 volts, so there is no problem.
Does that make sense?
Poolboy: Think of it this way:
Everything that is connected to the electrical service has about 1-4 volts on it. That is because the utility is using the earth a parallel path for nuetral current. So, the pool motor gets connected to the service equipment because it has to. We then might have 1-4 volts in the water. By bonding the pool steel to the ladder and the deck and everything else, we are basically intentionaly energizing them! We are trying to put voltage on these metal parts! The reason for this is to make the swimmer just like the bird on a wire...everything you touch is 3 volts, so there is no problem.
Does that make sense?
hey_poolboy
Senior Member
- Location
- Illinois
Re: Equal potential/pools
Ryan,
Yes, that makes sense. I'm not so confused about the need or proper function of the bonding grid as a whole. The '05 code stipulates that if there is no structural steel in the pool shell itself that a copper grid shall be placed under the pool in addition to the conventional bonding, and I don't understand that.
If there is not sructural steel in the shell of the pool and the pool is fiberglass what added benefit is there in this additional grid under the pool?
Ryan,
Yes, that makes sense. I'm not so confused about the need or proper function of the bonding grid as a whole. The '05 code stipulates that if there is no structural steel in the pool shell itself that a copper grid shall be placed under the pool in addition to the conventional bonding, and I don't understand that.
If there is not sructural steel in the shell of the pool and the pool is fiberglass what added benefit is there in this additional grid under the pool?
bphgravity
Senior Member
- Location
- Florida
Re: Equal potential/pools
Exactly what section are you getting this requirement from in the 2005 NEC?
hey_poolboy
Senior Member
- Location
- Illinois
Re: Equal potential/pools
680.26,C,3
The copper grid comes into play when you don't have 1 or 2
680.26,C,3
The copper grid comes into play when you don't have 1 or 2
lainspector
Member
- Location
- Ohio
Re: Equal potential/pools
Trying to understand the specifics of 680.26(c)(3) Alternate Means. Does this mean that "you must provide a field installed equipotential bonding grid" if you do not have one. For example; with fiberglass pools, plastic above-ground pools, non-metal pools, and the rest of those kind of pools (all permanent installed pools). I might need some help finding where this come from and why now??
Trying to understand the specifics of 680.26(c)(3) Alternate Means. Does this mean that "you must provide a field installed equipotential bonding grid" if you do not have one. For example; with fiberglass pools, plastic above-ground pools, non-metal pools, and the rest of those kind of pools (all permanent installed pools). I might need some help finding where this come from and why now??
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