Equipotential Bonding System Connected To Grounding System?

[Psychlo]

Is the bonding system for an indoor permanently installed therapeutic pool required to be connected to the premises grounding system? The pool manufacturer says NO and strongly advises against connecting the two systems (claiming nuisance tripping of the GFI may result). They want me to drive in a separate ground rod and connect the bonding system only to it.
The local (state) AHJ says YES and insists on connecting the two systems, citing 680.26(B)(6)(a).
I've always assumed the two systems should be connected, but have never been challenged on the point until now.

680.26(B) states that "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."

What am I missing here? It sounds like the NEC allows the connection of the two systems, but does not require it. As a seasoned electrician, that runs counter to what my gut tells me. Though I instinctively tend to agree with the AHJ's conclusion, their code reference does not satisfy. 680.26(B)(6)(a) only applies to double-insulated water pump motors (which, due to its specificity, doesn't answer my question at all). I told them I'd do it because, after all, they have absolute authority. But I want to know if there is an NEC article that makes it clear that the two systems indeed are required to be connected.

 

[texie]

The purpose of equipotential bonding is to assure that there are no voltage gradients between metallic objects. It is not a grounding electrode system. As 680.26(B) indicates it is not required to be connected to the GES. As a practical matter it likely will be due to connection to electrical equipment that have EGC conductors. The AHJ is incorrect.

 

[ActionDave]

....What am I missing here? It sounds like the NEC allows the connection of the two systems, but does not require it. As a seasoned electrician, that runs counter to what my gut tells me. Though I instinctively tend to agree with the AHJ's conclusion, their code reference does not satisfy. 680.26(B)(6)(a) only applies to double-insulated water pump motors (which, due to its specificity, doesn't answer my question at all). I told them I'd do it because, after all, they have absolute authority. But I want to know if there is an NEC article that makes it clear that the two systems indeed are required to be connected.

I agree with texie. The NEC is very clear that the equipotential wire and bonding need not be connected to the building grounding system. Like texie said it is not a grounding electrode system. It is also not part of the equipment grounding system; it's not there to clear a fault. That's the part that runs counter intuitive to what we almost always do as electricians.

 

[infinity]

They are not required to be directly connected but as the others have stated they are anyway once you bond the pump motor that has an EGC run with the branch circuit to the motor.

 

[david]

I agree they are not required to be directly connected together

we are however required to insure a connection to a pool branch circuit equipment ground, one of the benefits of doing this for some swimming pools, you insure that the pool water has a equipment ground reference and is not a big plastic bucket of water

 

[kwired]

Pool mfr and inspector are both wrong. Eq bonding is to prevent voltage gradients between points of contact to the user. We don't even care what voltage to true ground is for this purpose and the entire pool could be sitting there at 1000 volts to ground and it has still done what it was intended to do.

Inherently it will be connected to the electrical system ground via EGC of any electrical equipment associated with the pool water - at very least this is usually a pump. but that EGC can have a reference to true ground also, all it takes is some voltage drop on the grounded service conductor, or voltage drop on POCO MGN and you will have some voltage to true ground, most of the time is it only a slight voltage but it don't take much for it to be a problem in a pool environment.

 

[Psychlo]

So....it seems that it effectively IS required to connect the bonding system to the premises grounding system, but not "directly". This seems to be based on the assumption that they will be tied together via the electrical equipment EGCs, that being a pump motor, heater, etc. -- as has been stated above. And that would explain the 680.26(b)(6)(a) requirement that the bonding conductor must connect directly to the EGC of the double-insulated pump if there is no other connection between the bonding system and premises grounding system. Otherwise, what would be the purpose of this requirement to connect the two here?. It must be because there is an understanding (though I can't find it written anywhere in the NEC) that there is supposed to be a connection. Why else would only a double-insulated pump be required to have its ground connected to the bond conductor, and that only when there is not already another connection point in the system?

Jeepers. Seems they could have made this much more clear in the Code. Up here in the NW, pools are few and far between, so I don't do a lot of them. In my research I found that there is a WIDE diversity of understanding of this subject among professionals. And these are folks who are very fluent in Code-speak.

 

[ActionDave]

...... In my research I found that there is a WIDE diversity of understanding of this subject among professionals. And these are folks who are very fluent in Code-speak.

That is because among those fluent in Code speak are an astonishing number of folks that have a lack of understanding of electrical theory. The code is clear that the function of the pool equipotential bonding grid is not fault clearing. It is there to eliminate voltage gradients to make sure that nobody in the water can get shocked no matter what the source of voltage and whether or not it ever goes away.

 

[Psychlo]

That is because among those fluent in Code speak are an astonishing number of folks that have a lack of understanding of electrical theory.

Amen.

Though I feel obligated to place some blame at the feet of the code writers on this one. It appears that there is an underlying assumption that the two systems be connected, though it is not written anywhere (that I can find). Perhaps a reintroduction of the Fine Print Note would go a long way toward clearing up some of the misunderstandings of the more intricate code articles. Not a whole Handbook -- just a few notes here and there. After all, a codebook is more valuable if you understand the intent behind what you are reading. And understanding = safety, if applied.

 

[jusme123]

That is because among those fluent in Code speak are an astonishing number of folks that have a lack of understanding of electrical theory. The code is clear that the function of the pool equipotential bonding grid is not fault clearing. It is there to eliminate voltage gradients to make sure that nobody in the water can get shocked no matter what the source of voltage and whether or not it ever goes away.

Well said Dave, that to has been my understanding of the equipotential bonding grid

 

[kwired]

Pool is naturally going to take on earth potential, especially a metallic or concrete shell pool, but even non metallic shell will take on that potential with some capacitance involved because of the insulating shell.

Problem is most places use MGN power distribution at the utility level, as well as a grounded service conductor that often is also a normal current carrying conductor. The fact it is carrying current means there will be voltage drop and that voltage to earth will be imposed on all items connected to it via the main bonding jumper, which leaves any path between the pool and electrical system subject to that voltage. If a user comes in contact between two points of different potential they are subject to shock.

Pool pump is most likely electrical item to exist in nearly all pools and associated items handling the pool water. Bonding the pump to both the EGC and the EPBS puts them at same potential and that way there is nothing a pool user can touch that isn't at the same potential regardless of what the voltage to true ground may be. Entire pool grounding/ bonding system can be a few hundred volts to ground and users should never know it.