Question about the pool bonding jumper 680.23 (2)(b)

[wlnorris]

This is more of an engineering question about what NEC describes. So if you look at a cutaway diagram of what they describe, you have a lug, which on the inside, gets this #8 bonding jumper, and on the outside, your pool bond connects to it. Then you run this bonding jumper back up to your lighting junction box. There, it connects to the aluminum bar where your equipment grounds connect.

So it is a jumper between bonding loop and equipment ground.

So you are connecting your bonding loop for the entire pool, to your equipment ground; for the light circuit at least, but ultimately to all your equipment grounds, because they all probably tie to the same bar back in your panel somewhere.

But what if someone took their bonding loop, which also connects to a bonding loop lug on your lighting junction box, and then from there, put in a short jumper to the equipment ground bar?

What is the different in protection between those two methods? I'm having trouble visualizing a difference. Both are your entire bonding loop getting connected to equipment ground, in the same place.

The only obvious difference I see is the jumper in a conduit is less likely to be cut by digging or drilling, since it is in conduit. Maybe less likely to be disconnected since one end is underwater behind a light.

So I see some mechanical reasons for this, but would there be an actual difference in electrical protection, in a correctly connected, undamaged system?

 

[wlnorris]

Specifically, I am referring to a junction box like the Intermatic PJB2175 . It has an external bonding lug, with a copper bar that connects the bond loop to the equipment ground terminals inside the box. So connecting your bonding loop to that terminal will also connect the light's equipment ground to the bonding loop, similar to using the bonding loop jumper.

You end up with a small copper bar as your bonding jumper instead of a piece of submerged copper that may be more likely to corrode.

Pros and cons?

 

[augie47]

The line between "bonding" and "grounding" is sometimes a big vague.
The bare copper wire connecting to various pool metallic items and the wet-niche light (external) is for bonding whereas the pool junction box and those conductors connected to it ares specifically for grounding. (There are some items such as the wet niche and pump that are both bonded and grounded)
If you had no electrical associted with the pool, the bonding would still be required to assure erquipotential bonding,

 

[wlnorris]

The line between "bonding" and "grounding" is sometimes a big vague.
The bare copper wire connecting to various pool metallic items and the wet-niche light (external) is for bonding whereas the pool junction box and those conductors connected to it ares specifically for grounding. (There are some items such as the wet niche and pump that are both bonded and grounded)
If you had no electrical associated with the pool, the bonding would still be required to assure erquipotential bonding,

Yes, I get that, but the bonding jumper in question is a jumper between the bonding system and grounding system. It connects to the same lug in the niche as the bonding connector (just inside instead of outside), then runs up and connects to the same bar as equipment ground in your junction box.

Essentially, this jumper makes all your electrical equipment at equipotential, even those without bonding lugs, as long as your equipment grounds are done properly. It bonds your equipment grounds.

So it is a jumper between bond and equipment ground, made between the niche and lighting junction box. However, with a junction box like the PJB2175, the same jump between bond and equipment ground is made, just in a different location.

Are there pros and cons of one vs the other? Any pros and cons of having both at the same time (can any sort of ground loops (or maybe bond loops in this case) be created under certain failures)?

 

[augie47]

If I read correctly and you are questioning a "jumper" between the 680.26 bonding conductror and the pool light junction box, I don't see a Code requirement for such and have not seen it on any installs. Perhaps I misunderstand your reference.

 

[wlnorris]

If I read correctly and you are questioning a "jumper" between the 680.26 bonding conductror and the pool light junction box, I don't see a Code requirement for such and have not seen it on any installs. Perhaps I misunderstand your reference.

No, as I stated it is 680.23.

(b) Nonmetallic Raceway. A nonmetallic raceway to the forming shell must contain an 8 AWG insulated (solid or stranded) copper bonding jumper that terminates to the forming shell and junction box unless a listed low-voltage lighting system not requiring grounding is used.

It is a jumper between the bonding system and equipment ground.

 

[wlnorris]

So the question is, what would the difference be between this:



and this



Other than the obvious that one is in conduit and one isn't.

A local pool installer that I asked has told me he has installed over 300 new inground pools using plastic niches and he has never put the bonding jumper in any of them through the non-metallic conduit. He attaches the bonding loop/grid to a bonding lug on the deck box he uses as shown in the 2nd pic. He says he has never been questioned by an inspector or required by one to install the bonding jumper through the non-metallic conduit.

He further added that he thought it was dumb to do so. He has been called in to work on pools that have had the potted connector, and every time it is because the connection has corroded or broke inside the non-metallic niche. Now those systems don't have that bond to the light equipment ground at all. And there is no way to repair that in the niche and requires the niche to be replaced, which is a major expensive repair.

Instead of replacing the niche, he repairs it by connecting the system using the 2nd method above. He says at worst, sometimes they have a junction box with no external bonding lug and he has to replace the j-box.

Electrically, I don't see a difference between the two methods. I was wondering why code made the connection so specific, when they could just say something like, "The equipotential bonding grid must have a jumper connecting it to the lighting equipment ground for the wet luminaire." Then the location could be left to the installer, either through the conduit or through the J box.

I guess I can see that this could be too generic. Then in theory they could run the jumper back to the panelboard and comply. While that should work electrically, it would mean that in the diagram above, there are a couple of places a ground wire could be removed, and then your light equipment ground may not be properly bonded.

Maybe the potential for wiring error increases the further the you make the connection from the light, which is in water and maybe the most dangerous component. This installer I spoke with runs the external niche bonding wire directly back to the J-Box bonding external lug in a homerun. Then he ties any other connections to the bonding grid/loop directly back to this home run by the J box.

What are the pros and cons of one method vs the other?

I'm just wondering if there are 300+ pools out there with a safety hazard. The installer recognized the need for the jumper, but had apparently never placed it in the specific location NEC code specifies (as appears to have specified at least as far back as 2008 in the copies I checked).

 

[wlnorris]

In the two examples above, both have one end of a bonding jumper in a hard to reach location (one the back of the niche (buried) and the other behind a pool light (underwater). Unlikely either will be disconnected by a user,

One runs through a conduit and terminates inside the J-Box, but there is a potential for a user to disconnect and forget to reconnect.

The other runs through the earth and daylights by the J Box and terminates outside the J-Box, but there is potential for a user to disconnect this external connection.

So in either case, there is one inaccessible connection and one connection that could be accidentally disconnected while servicing, both between the same two components. So it seems to be like his method is basically equal to the NEC method, but was just looking for other opinions.

It was an interesting situation that I ran across and found it interesting that no city, county, or state inspector has ever called it out on him. I guess local authorities are free to enforce or not enforce parts of the NEC, and I wonder if this is something that at some local level, a decision was made to to follow NEC.

He also made a claim that his method was safer with NEC, but I am still trying to wrap my head around his claim. I'm not sure I understood it and it was pretty oddball. Basically something along the line of imagining that someone went through the non-metallic conduit with something like an iron digger. The tool goes through the lights cable assembly, only cutting the hot wire in half, and the circuit is still complete through the tool.

Then it does through the bonding jumper too. But in that case, the portion of the jumper running to the niche remains in contact with the tool (so hot a bonding jumper are now connected together, but the portion of the jumper running to the j box pulls away from the tool and has no connection.

He claimed that in this odd scenario, it would be safer had the bonding jumper not be there at all (something about energizing the niche).

Still trying to wrap my head around that part of his claim.