Dock wireing disconcts

[Cavie]

:-? Since I began my quest to understand ART 682, I have Run into a very small problem with one boatlift builder. He states in is install instructions that ALL wireing the lift shall be disconected including the ground wires. He stated that someone in Monroe County Fl. sells such a disc. Has anyone ever heard of this?. I cannot believe anyone would pass this install. It won't be an issue here as of OCT 1. because 682 prohibits it and requires a #8 bond to all metal bonded back to the service ground bar. He is stating that if it is not disconected that the lift will be eaten up with electrolisis. He has stated he will have to fight the county on 682. I said he will hace to fight the NEC.

 

[barbeer]

I have not heard that one. Definitely the EGC and not the neutral?

 

[boater bill]

I am going to bet the manufacturer is confused. I also wonder if they are using a 3-pole disconnect and using the unused switch to break the ground. I'll be certain it is not UL listed for that application.
If his lifts have galvanic corrosion, tell to to include a Guppy zinc to hang off the lift.

View attachment 783

 

[jwelectric]

because 682 prohibits it and requires a #8 bond to all metal bonded back to the service ground bar.

I am sorry but I don?t completely agree with this statement.

682.33(C) states that the equipotential planes shall be bonded to the electrical grounding system not the electrode system.

The rule for supplying the equipment grounding conductor for the feeders or branch circuits is found in 682.31(B) & (C) respectively.
The equipment grounding conductor for feeders must land in the service but the branch circuits can land in the remote panel board they originated unless the device or equipment is required to have an isolated equipment grounding conductor.

 

[Cavie]

I am sorry but I don?t completely agree with this statement.

682.33(C) states that the equipotential planes shall be bonded to the electrical grounding system not the electrode system.

The rule for supplying the equipment grounding conductor for the feeders or branch circuits is found in 682.31(B) & (C) respectively.
The equipment grounding conductor for feeders must land in the service but the branch circuits can land in the remote panel board they originated unless the device or equipment is required to have an isolated equipment grounding conductor.

682.32 Bonding of Non-current-carrying metal Parts
All metal parts in contact with the water, all metal piping ,Tanks, and all non-current carrying metal parts that may become energized shall be bonded to the grounding bus in the panel board.

They do not tell you what size to do this bonding but since the equipotential plane maust be # 8 we must asume that the bonding of metal parts is also to be #8.

 

[Cavie]

I have not heard that one. Definitely the EGC and not the neutral?

He wants all wires disconected. He tried this one another project with 12 docks. He installed 3PH standard duty knife switches and was running 220 to the motors and disconecting the ground thru the 3rd blade. I had the house electrican remove the disc. Before I would pass final on the condos.

 

[dbuckley]

You know, given the asinine multigrounded neutral arrangement that is probably upstream of the lift (in the electrical rather than the hydraulic sense), having a ground disconnect may actually be the safest approach, despite the fact that such a thing not only goes against the grain, but against the NEC as well.

How often is there a thread entitled something like getting shocks from metalwork near water...?

 

[jwelectric]

682.32 Bonding of Non-current-carrying metal Parts

All metal parts in contact with the water, all metal piping ,Tanks, and all non-current carrying metal parts that may become energized shall be bonded to the grounding bus in the panel board.

They do not tell you what size to do this bonding but since the equipotential plane maust be # 8 we must asume that the bonding of metal parts is also to be #8.

This is a long way from what you said earlier. What you said in your original post was;

because 682 prohibits it and requires a #8 bond to all metal bonded back to the service ground bar.

The section you quote above 682.32 clearly states to the grounding bus in the panel board

682.32 Bonding of Non-current-carrying metal Parts

All metal parts in contact with the water, all metal piping ,Tanks, and all non-current carrying metal parts that may become energized shall be bonded to the grounding bus in the panel board.

This panel board should be the same panel which the branch circuit originates 300.3(B).

If there was no electrical at the dock there would be no requirement for all the bonding. 250.32 mandates that a grounding electrode system be installed at this remote panel and all the grounding conductors would be bonded back to the disconnecting equipment and the electrode system there so to disconnect the equipment grounding conductors that is installed with the feeder I can?t see as a problem.
Remember that all the bonding of metal and the equipotential planes are to keep everything at the same potential not to connect it to anything such as the service.

 

[John Valdes]

How often is there a thread entitled something like getting shocks from metalwork near water...?

Several months ago I was involved in wiring a sub panel for a boathouse on a lake. The dock is to be wired in the near future.
The next door neighbor had his dock already done. (Wired) I did not do the work.
He called me one day and asked why he was getting shocked when he touched the swimming ladder. Since the project is over 100 miles away I referred him to a local contractor that I know. Have not heard any thing YET?

But in the process of doing the sub panel job I was in close contact with the AHJ. He had me do something I would have never imagined. He strictly prohibited a grounding electrode at the boathouse. He only allowed the ECG from the main panel.
Now I am wondering if he was on to something?

 

[Cavie]

Several months ago I was involved in wiring a sub panel for a boathouse on a lake. The dock is to be wired in the near future.
The next door neighbor had his dock already done. (Wired) I did not do the work.
He called me one day and asked why he was getting shocked when he touched the swimming ladder. Since the project is over 100 miles away I referred him to a local contractor that I know. Have not heard any thing YET?

But in the process of doing the sub panel job I was in close contact with the AHJ. He had me do something I would have never imagined. He strictly prohibited a grounding electrode at the boathouse. He only allowed the ECG from the main panel.
Now I am wondering if he was on to something?[/quote]

Yep. 682.31 (C). and lets not forget the equipotential plane while we're doing all this wireing. Or the auto disconect float sw service disc for floating structures. We having fun yet?

 

[boater bill]

That 682 question came up in a discussion today.

It seems the Florida Building Officials are going to render an interpretation on that requirement for navigable waters. 682 was intended for decorative submerged fountains and such on manmade lakes etc. It was never intended for boat lifts, but is sometimes being interpreted that way.

I am sure more is to come on that one.

 

[dbuckley]

That ignores 682.33(A), which requires an equipotential plane (effectively) around the panel, and thats going to require at a minimum ground rods and maybe a copper ring, like a pool.

The puzzle is section B - why the equipotential zone is not required to include the equipment fed from the panel, and by logical extension and where present, the water immediately adjacent to the equipment. The RCD requirement is sensible, but completely ignores the fact that lack of an equipotential zone presents a shock hazard from differing ground potentials.

 

[Cavie]

That 682 question came up in a discussion today.

It seems the Florida Building Officials are going to render an interpretation on that requirement for navigable waters. 682 was intended for decorative submerged fountains and such on manmade lakes etc. It was never intended for boat lifts, but is sometimes being interpreted that way.

I am sure more is to come on that one.

682.2 Definitions
Electricial Datum Plan
(4) the electrical datum plane for floating structures and landing stages......

what is a floating dock if not a floating structure or a landing stage?????

One must read this artical in its entirety in order to understand it. and apply everything in it not just one section as we all do with the rest of the code. It is very poorly written.

 

[Cavie]

That ignores 682.33(A), which requires an equipotential plane (effectively) around the panel, and thats going to require at a minimum ground rods and maybe a copper ring, like a pool.

The puzzle is section B - why the equipotential zone is not required to include the equipment fed from the panel, and by logical extension and where present, the water immediately adjacent to the equipment. The RCD requirement is sensible, but completely ignores the fact that lack of an equipotential zone presents a shock hazard from differing ground potentials.

Ground rods are not stated in the artical. Equipotential plane is wire mesh or other conductive elements embeded in or placed under the walk surface. No copper ring is mentioned. Equipment fed from the panel. How would you install a grid around a floating fountian pump??

 

[dbuckley]

You are being too strict on your definition of an equipotential area, based on the realities of how its done for a pool.

There are two base concepts behind an equipotential zone; the first is to provide an alternative, lower impedance path to current that wishes to flow across the zone, rather than through the soil, concrete or whatever is in the zone. So, for example, a circle of ground rods joined by copper will achieve that goal. One then generally electrically aligns the entire zone with some reference point, by adding a bond to some ground point.

Taking your example of a floating fountain pump, you want the entire water volume and the surrounding soil to be equipotential, so a series of bonded ground rods around the area would be an answer. However, I would argue that a typical floating fountain pump doesn't need to be in an equipotential zone, as they typical floater doesn't have a ground wire, and thus you cant get a ground-to-ground shock. The RCD will save the day if something goes wrong.

Taking the dockside lift, you want the water and surrounding soil to be equipotential with the metalwork of the structure, as that is metallic and conductive, and there is always scope for a ground-to-ground shock. So use of ground rods and/or copper rings achieves that aim.

 

[Cavie]

You are being too strict on your definition of an equipotential area, based on the realities of how its done for a pool.

There are two base concepts behind an equipotential zone; the first is to provide an alternative, lower impedance path to current that wishes to flow across the zone, rather than through the soil, concrete or whatever is in the zone. So, for example, a circle of ground rods joined by copper will achieve that goal. One then generally electrically aligns the entire zone with some reference point, by adding a bond to some ground point.

Taking your example of a floating fountain pump, you want the entire water volume and the surrounding soil to be equipotential, so a series of bonded ground rods around the area would be an answer. However, I would argue that a typical floating fountain pump doesn't need to be in an equipotential zone, as they typical floater doesn't have a ground wire, and thus you cant get a ground-to-ground shock. The RCD will save the day if something goes wrong.

Taking the dockside lift, you want the water and surrounding soil to be equipotential with the metalwork of the structure, as that is metallic and conductive, and there is always scope for a ground-to-ground shock. So use of ground rods and/or copper rings achieves that aim.

I can't make someone install ground rods, it is not in the code.
No! the pump does not require the bond grid, the Disconect and panel does as per 682. And the typical floating pump must have a ground.

 

[hardworkingstiff]

When reading 682.1, I am of the opinion that 682 would not apply to floating docks or boat lifts at a marina, 555 would apply.

Reading 555.1, I am of the opinion that 682 would apply to a "private, noncommercial docking facility constructed or occupied for the use of the owner or resident of the associated single-family dwelling" since it is excluded by 555.

 

[dbuckley]

I can't make someone install ground rods, it is not in the code.

Absolutely. Which gets us right back to topics with titles like "when I'm in the water and touch something metal I get a shock". In these sorts of cases, "code compliant" is inadequate.

Which is why a non-compliant three pole disconnect that takes out the ground as well as the current carrying conductors is actually safer than a solidly bonded compliant installation.

I think we've now gone the full circle...

 

[Cavie]

Absolutely. Which gets us right back to topics with titles like "when I'm in the water and touch something metal I get a shock". In these sorts of cases, "code compliant" is inadequate.

Which is why a non-compliant three pole disconnect that takes out the ground as well as the current carrying conductors is actually safer than a solidly bonded compliant installation.

I think we've now gone the full circle...

Well maye you can get the code making panel to write that into the code.

 

[dbuckley]

I think I'd have a better chance of getting those funky current limiting receptacles mandated

The real problem is that once you leave the sanctity of an enclosed building, "ground" becomes a bit of a movable feast, and it is hard to determine exactly which cause of action is best, as many approaches are simply outlawed, and many approaches aren't very safe. Once you're outside of an equipotential zone then ground-to-ground shocks (a/k/a stray currents or stray voltages, depending who you talk to) become a real possibility.

I would submit that in this particular case the best (and again, non-compliant) approach is an isolating transformer, with the secondary not bonded to the upstream ground. The secondary should have a RCD and a ground rod, and the dock metalwork bonded to it. Removing the usual SDS bond to the upstream ground removes the possibility of a ground to ground shock. All the other bases are covered. Of course, the transformer itself would have to be appropriate and appropriately enclosed, and if its a metallic enclosure, then it should be adjacent to the panel and treated as per 682.33(A).


Now thats something you might be able to sell to the NEC panel...