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oldsparky52

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Wilmington, NC USA
I've wired some marinas, and with the shocks and deaths and code changes, I'm wondering about something.

A body of water can be a reasonable parallel path for current back to the PoCo distribution system or to a substation because they both are grounding the neutral to the earth (the substation even more sow than the distribution system).

If I understand the PoCo distribution wiring correctly, the neutral at the primary and the secondary are both grounded and possibly using the same GEC, right/wrong? If right, then a deteriorating primary neutral connection can cause higher resistance parallel paths back to the source (substation) using the earth or ... the water. And since we are working with such high voltages compared to the usage voltages, it doesn't take much of a deterioration to get a couple/three or more volts between the water and the PoCo neutral.

We ground the neutral at the service, which is usually a little bit away from the water. We know the resistance on the connection to ground is not very low, so there could easily be a voltage between the water and the system ground of the marina.

My thoughts are maybe we should be running a GEC to the water itself, but that just brings the water up to the neutral voltage, and if there is a deteriorating primary neutral close by, the water will get even more step voltage around the marina.

So, maybe we should ground the water AND monitor the GEC to the water for current. When there is enough current on that conductor (and I don't know how much that is) an alarm is sounded so it can be investigated.

Your thoughts?
 
A similar warning system is described in 250.21(B) for Ground Detectors.

Write a proposal, and submit for 2023 code cycle.

Or, patent a device that reliably detects current passing thru human bodies, and become a millionaire.
 
oldsparky52 said:
What do you think about grounding the service neutral to the water?
Click to expand...
By itself, that might be OK, but if there are earth grounds anywhere around the pool it would just create a gradient in the water.
Best is to create a proper equipotential system serving the pool area and effectively connect that to the EGC at the pump where both connections are required.

Sent from my XT1585 using Tapatalk
 
oldsparky52 said:
What do you think about grounding the service neutral to the water?
Click to expand...

A long tradition of bonding equipment in contact with water bodies is described in NEC 680.6,
and equipotential bonding grids in contact with water bodies 680.26, and other required "equipotential" bonding areas.

Stray current passing thru such grounding/bonded systems can trip adjustable circuit breakers & GFCI's.

Stray current passing thru neutrals don't trip breakers below overload, unless a yet-to-be-invented detection signature identifies electrocutions.

Perhaps we could call it a EFCI (Electrocution Fault Circuit Interrupter)

Local stray current can originate from many isolated sources, vessel generators, or batteries, etc.. Except for lightning events & High Voltage transients we don't expect the primary electrical service (neutral) to equipotential bond isolated or secondary sources of stray voltage, much less protect end users from damage.
 
GoldDigger said:
By itself, that might be OK, but if there are earth grounds anywhere around the pool it would just create a gradient in the water.
Best is to create a proper equipotential system serving the pool area and effectively connect that to the EGC at the pump where both connections are required.

Sent from my XT1585 using Tapatalk
Click to expand...

OP is talking about a body of water such as a lake, river, ocean. He didn't mention pool so I don't think you could accomplish anything trying to add an equipotential system to his scenario.
 
GoldDigger said:
By itself, that might be OK, but if there are earth grounds anywhere around the pool it would just create a gradient in the water.
Best is to create a proper equipotential system serving the pool area and effectively connect that to the EGC at the pump where both connections are required.

Sent from my XT1585 using Tapatalk
Click to expand...

Bad communication I guess, I was talking about the Intracoastal Waterway (or large lakes too). Mostly where marinas are.

Not talking about a pool. :(
 
ramsy said:
A long tradition of bonding equipment in contact with water bodies is described in NEC 680.6,
and equipotential bonding grids in contact with water bodies 680.26, and other required "equipotential" bonding areas.

Stray current passing thru such grounding/bonded systems can trip adjustable circuit breakers & GFCI's.

Stray current passing thru neutrals don't trip breakers below overload, unless a yet-to-be-invented detection signature identifies electrocutions.

Perhaps we could call it a EFCI (Electrocution Fault Circuit Interrupter)

Local stray current can originate from many isolated sources, vessel generators, or batteries, etc.. Except for lightning events & High Voltage transients we don't expect the primary electrical service (neutral) to equipotential bond isolated or secondary sources of stray voltage, much less protect end users from damage.
Click to expand...

I've seen a case where the aluminum gangway (that was bonded to the service ground) had a potential to the water that only left when the service neutral was lifted. We just read about a similar thing happening to someone else.

I was just wondering if we bonded the service equipment or the ground feeding a local sub panel to the water that might minimize any shock hazards that developed from the PoCo or the service equipment having bad connection issues.

Now maybe these incidents aren't enough to be concerned about, maybe not. I think it's great the NEC is addressing shock issues with the newer GF requirements, but that does not deal with a PoCo induced problem on the neutral and thereby grounding system of the service. Bonding the water to the service neutral should help reduce any hazards, and if the current on it was monitored, it could be an early warning of a fault developing (which if fixed early might help avoid a shock hazard).

Do I make sense, and is it a fix for a problem that really doesn't exist?
 
oldsparky52 said:
I've seen a case where the aluminum gangway (that was bonded to the service ground) had a potential to the water that only left when the service neutral was lifted..
Click to expand...
Makes sense to me. I've heard about shared sewer & plumbing dissipating neighbors low level faults into our equipment, and I've seen a few open service neutrals cause equipment to energize Phone/Cable D-Marks back to ground.

I'm sure Marina's are subject to similar problems, but Art. 555 for Marina's doesn't seem to require equipotential bonding, which is tied to neutral at main bonding, and has solved this problem for pools Art. 680, explosion proofing Art, 50X, agricultural live stock, & animal stables.
 
oldsparky52 said:
..if the current on it was monitored, it could be an early warning of a fault developing (which if fixed early might help avoid a shock hazard)
Click to expand...
Do remember Power Company finding a weather head leaking current to ground, after a client complained to me, and I clamp metered 2-3Amps on one of several electrode conductors in parallel.

Low level ground fault was probably there for years, and code requires no such warning system. A simple E-Mon D-Mon CT set to monitor electrode conductors might provide the needed alarm.
 
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