Pool bonding question

[FionaZuppa]

If we install a panel remote from the dwelling wouldn't we have to install ground rods for the panel? It is a separate structure, IMO so rods or ges would be required

what about a "spa" panel that has one 240v 50A gfci ocpd and also serves as the pool gear disco, which is out 50ft from the main panel and it just gets mounted to a block wall, where such panel is 15ft away from the pool gear. the sub is not technically in any remote structure. the sub enclosure itself would be tied to EGC. you need a rod for this?

 

[don_resqcapt19]

oi. if for whatever reason the egc at the pool gear goes south. having a separate tie from bonding over to sub panel provides the extra assurance. i have many times for many reasons seen egc copper at pool gear broken or useless. stab the earth with a ground rod at the sub, tie the egc and bond grid to the rod. done.

and no, a 10ft ground rod will not be like a short piece of copper/bronze connected to another 9ft of insulator!

If the bonding connection to the electrical system is gone, the addition of grounding electrode do not provide any increase in safety for the pool users. All it would do is add a bit more area, the area very close to the rod, as part of the area that has equipotential.

In your example of the wet kid stepping off the bonded deck on to the earth, the same think happens when you step away from the same thing happens when you step away from the small area around the ground rod.

I think that it is important to note that the grounding system acts as a current divider and not a voltage divider. That is the reason the ground rod cannot lower the voltage.

 

[don_resqcapt19]

and neither would a broken egc at the pool gear, right?

against code? please share.
from what i read, "...shall not be required...", which means "optional".
direct from the NEC code "the equipotential bonding required by this section shall be installed to reduce voltage gradients in the pool area"

Yes, it does say that, but it also requires the equipotential bonding conductor to be connected to the pool electrical equipment, so while there is not a requirement to physically run the bonding conductor to the electrical system, there is a requirement for an indirect connection via the equipment EGC(s). 680.26(B)(6)
Also look at:

680.26(B)(a) Double-Insulated Water Pump Motors. Where a double insulated water pump motor is installed under the provisions of this rule, a solid 8 AWG copper conductor of sufficient length to make a bonding connection to a replacement motor shall be
extended from the bonding grid to an accessible point in the vicinity of the pool pump motor. Where there is no connection between the swimming pool bonding grid and the equipment grounding system for the premises, this bonding conductor shall be connected to the equipment grounding conductor of the motor circuit.

 

[FionaZuppa]

Yes, it does say that, but it also requires the equipotential bonding conductor to be connected to the pool electrical equipment, so while there is not a requirement to physically run the bonding conductor to the electrical system, there is a requirement for an indirect connection via the equipment EGC(s). 680.26(B)(6)
Also look at:

i guess i cant convey it well enough via words.

you have a sub panel (aka "spa panel-ocpd/disco") 20ft from pool gear. you carry over egc to pool pump frame. your pool area is bonded per nec and that bonding is tied "in the vicinity of the pump". so now you have bonding tied to egc indirectly. now, over the next year or so the egc on the pump corrodes or breaks off, but in a non-obvious way. the egc is now lost at the pool gear, and now gfi may not trip properly.

so, how to avoid that? stick a rod in ground at the sub panel, tie panel box to the rod, tie bond grid to the rod.

how does the rod help? lets just say a 20ft rod gets me 30ohms. the egc is completely lost for whatever reason. the 240vac does a high ohms short to the bond grid. the bond grid will flow some current to the rod, and because you have a high ohms to low ohms divider the voltage on the bonding will be low. you still have equi on the grid, so from that view its still good, but you dont have 240vac on the bonding.

next is if the egc is lost, rod provides 30ohms, 240vac does a low ohms short to bonding (still safe w/o rod right? no.), the rod flows 8A, gfi trips at its rated mA, etc.

so, one ~10-20ft rod and some extra bare copper wire simply makes the install safer.

 

[Little Bill]

i guess i cant convey it well enough via words.

you have a sub panel (aka "spa panel-ocpd/disco") 20ft from pool gear. you carry over egc to pool pump frame. your pool area is bonded per nec and that bonding is tied "in the vicinity of the pump". so now you have bonding tied to egc indirectly. now, over the next year or so the egc on the pump corrodes or breaks off, but in a non-obvious way. the egc is now lost at the pool gear, and now gfi may not trip properly.

so, how to avoid that? stick a rod in ground at the sub panel, tie panel box to the rod, tie bond grid to the rod.

how does the rod help? lets just say a 20ft rod gets me 30ohms. the egc is completely lost for whatever reason. the 240vac does a high ohms short to the bond grid. the bond grid will flow some current to the rod, and because you have a high ohms to low ohms divider the voltage on the bonding will be low. you still have equi on the grid, so from that view its still good, but you dont have 240vac on the bonding.

next is if the egc is lost, rod provides 30ohms, 240vac does a low ohms short to bonding (still safe w/o rod right? no.), the rod flows 8A, gfi trips at its rated mA, etc.

so, one ~10-20ft rod and some extra bare copper wire simply makes the install safer.

The EGC has nothing to do with the GFCI tripping.

 

[FionaZuppa]

The EGC has nothing to do with the GFCI tripping.

how do you mean? where would amps flow if you didnt have another path for it to flow through?

 

[Little Bill]

how do you mean? where would amps flow if you didnt have another path for it to flow through?

It would flow through (or try to) whatever it faulted to. You could leave the EGC disconnected or cut it off and if there was an imbalance in current the GFCI would trip. Same reason you can replace a 2-prong/wire receptacle with a GFCI.

 

[ActionDave]

Same reason you can replace a 2-prong/wire receptacle with a GFCI.

Ooooh, that's one of his hot buttons. Don't go there.

 

[don_resqcapt19]

how do you mean? where would amps flow if you didnt have another path for it to flow through?

If it doesn't have a path to flow on you can't become part of a path. Assuming GFCI, it will still trip anytime you flow ~5mA to ground...if you are not flowing 5mA there really isn't a hazard. I don't see any benefit to installing grounding electrodes for pools.

 

[kwired]

i guess i cant convey it well enough via words.

you have a sub panel (aka "spa panel-ocpd/disco") 20ft from pool gear. you carry over egc to pool pump frame. your pool area is bonded per nec and that bonding is tied "in the vicinity of the pump". so now you have bonding tied to egc indirectly. now, over the next year or so the egc on the pump corrodes or breaks off, but in a non-obvious way. the egc is now lost at the pool gear, and now gfi may not trip properly.

so, how to avoid that? stick a rod in ground at the sub panel, tie panel box to the rod, tie bond grid to the rod.

how does the rod help? lets just say a 20ft rod gets me 30ohms. the egc is completely lost for whatever reason. the 240vac does a high ohms short to the bond grid. the bond grid will flow some current to the rod, and because you have a high ohms to low ohms divider the voltage on the bonding will be low. you still have equi on the grid, so from that view its still good, but you dont have 240vac on the bonding.

next is if the egc is lost, rod provides 30ohms, 240vac does a low ohms short to bonding (still safe w/o rod right? no.), the rod flows 8A, gfi trips at its rated mA, etc.

so, one ~10-20ft rod and some extra bare copper wire simply makes the install safer.

If you have a concrete pool with concrete decking and have all the metallic re-enforcement within all that concrete bonded together you think your 30 ohm rod is less resistance to earth??

You have the wrong idea about what all this equipotential bonding is all about, it isn't about clearing faults, it is about making everything within reach of a pool user the same potential. The pool user is like a bird on a high voltage line, if he can't touch anything that is at different potential he is not exposed to any electrocution hazard, even if he is 7200 volts above earth potential.

Bring the equipotential bonding system of the pool up to 7200 volts over surrounding earth and people in the pool are not at any risk if the equipotential bonding doesn't have any "holes" in it. Adding a 30 ohm ground rod won't make any difference within the pool area either, it will create voltage gradients around the rod though, and you probably would not want to take very big steps near the rod or you may cross some pretty high voltage between each foot, even with your shoes on while the guys in the pool are just fine.

If POCO has voltage drop on their MGN or even if you have some significant voltage drop on your service neutral, any EGC running to the pool equipment will have a voltage to ground that is equal to this voltage drop - so a pool is often running at least with a slight voltage over surrounding earth if it has a connection to the electrical system grounded conductor(s).