Just bought a place and want some more opinions on what i have and if its correct. Metal frame dock, walkway and swim ladder are bonded #6, top of walkway at shore bonded to ground rod with #6. Stiff arm on other end of dock is not bonded. I believe it should be. Outdoor panel at top of walkway at shore is a main lug panel fed from the house, 4 wire system on standard two pole breaker. 4 gfci breakers in outdoor panel feeding individual branch circuits on the dock. All device boxes on the dock are bonded and made up to the ground bar in the outdoor panel, however the ground source for the outdoor panel is the ground coming from the house. It is not bonded to the ground rod. Neutral and ground are not bonded in the outdoor panel, I don't believe they should be, however I feel like the ground bar should also have a #6 going to the rod. Confused about the rule stating the feeder has to have its own egc. Also should there be a main breaker in the outdoor panel? Code states there must be a disconnecting means at the shoreline/top of walkway, do the breakers count as a disconnecting means or are they trying to specify ONE disconnect to de energize everything??
Residential dock grounding
- Thread starter JB85
- Start date
A photo would help. A dock panel (like on the dock at a marina) are typically protected by a Ground Fault Protection of Equipment (GFPE) feeder breaker and don't require a ground rod. A panel at a residence up away from the dock on say a equipment shack would have a ground rod and not need a GFPE breaker though I have seen them with GFPE breakers. See NEC articles 555 and 682 especially 682 part II and 555.53.
correct see explanation below
yes may not need to be a #6 but yes
It says your a substation electrician which I take to mean you work on the utility side which is a 'Multi Grounded Neutral' or (TN-C) system where neutral and protective conductor functions are combined into one bare wire.
In a NEC system after the service disconnect a MGN (TN-C) system is no longer used. The standard is to separate the neutral from the 'equipment grounding' or protective conductor creating a TN-C-S system, so a feeder would treat a neutral as if its 'live' and its only job now is carry neutral current, and the 'equipment ground' AKA protective conductor is used to bond all metal parts, ground rods etc.
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Eddie702
Licensed Electrician
- Location
- Western Massachusetts
- Occupation
- Electrician
I would assume with 4 breakers in the panel you shouldn't need a main breaker as you can kill the power with 4 hand movements. Usually 6 is allowed.
Fred B
Senior Member
- Location
- Upstate, NY
- Occupation
- Electrician
What you have is covered under 555.13
555.13 Bonding of Non-Current-Carrying Metal Parts.
All metal parts in contact with the water, all metal piping, and all non-current-carrying metal parts that are likely to become energized and that are not connected to a branch circuit or feeder equipment grounding conductor, shall be connected to the grounding bus in the panelboard using solid copper conductors; insulated, covered, or bare; not smaller than 8 AWG. Connections to bonded parts shall be made in accordance with 250.8.
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 are likely to become energized shall be bonded to the grounding terminal in the distribution equipment.
Also you mention a swim ladder so might want to contemplate the point made in 555.10 sign requirement and the Mike Holt references below.
555.10 Signage.
Permanent safety signs shall be installed to give notice of electrical shock hazard risks to persons using or swimming near a docking facility, boatyard, or marina and shall comply with all of the following:
(1) The signage shall comply with 110.21(B)(1) and be of sufficient durability to withstand the environment.
(2) The signs shall be clearly visible from all approaches to a marina, docking facility, or boatyard facility.
(3) The signs shall state “WARNING — POTENTIAL SHOCK HAZARD — ELECTRICAL CURRENTS MAY BE PRESENT IN THE WATER.”
If you are providing power out to the dock there is a potential for ESD Mike Holt video:
555.13 Bonding of Non-Current-Carrying Metal Parts.
All metal parts in contact with the water, all metal piping, and all non-current-carrying metal parts that are likely to become energized and that are not connected to a branch circuit or feeder equipment grounding conductor, shall be connected to the grounding bus in the panelboard using solid copper conductors; insulated, covered, or bare; not smaller than 8 AWG. Connections to bonded parts shall be made in accordance with 250.8.
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 are likely to become energized shall be bonded to the grounding terminal in the distribution equipment.
Also you mention a swim ladder so might want to contemplate the point made in 555.10 sign requirement and the Mike Holt references below.
555.10 Signage.
Permanent safety signs shall be installed to give notice of electrical shock hazard risks to persons using or swimming near a docking facility, boatyard, or marina and shall comply with all of the following:
(1) The signage shall comply with 110.21(B)(1) and be of sufficient durability to withstand the environment.
(2) The signs shall be clearly visible from all approaches to a marina, docking facility, or boatyard facility.
(3) The signs shall state “WARNING — POTENTIAL SHOCK HAZARD — ELECTRICAL CURRENTS MAY BE PRESENT IN THE WATER.”
If you are providing power out to the dock there is a potential for ESD Mike Holt video:
Yes we do gave a grounded neutral on most everything. I see with it being a 4 wire system from the house panel to the outdoor panel, and not having the NG bond outside, the neutral is current carrying all the way back to the panel in the house. All the way to the meter base actually, the service from the meter to the house is 4 wire with the NG bonded in the meter base. My confusion was seeing code requiring the ground with the feeder, and I have a ground established with the ground rod at the top of the walkway, yet they're not tied together. I wasn't sure if that was something that was incorrect or if it was supposed to be that way. At the moment the only thing the ground rod is doing is basically making the dock structure and walkway at ground potential. Almost like they have two separate ground systems, like one serving as GEC and one as EGC. In my world we bond at all ground points to keep and even potential across the yard
Ok so I simply need to run from the ground bar in the outdoor panel to the ground rod. We use #4 on our meter bases so I'll grab some of that. I have the signs. Thanks
I thought 6 was the magic number but its been about 15 years since I did commercial work. I couldn't find anything real cut and dry in the codebook about it. Thanks
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
This is nothing like a substation though. Workers in substation are wearing insulated sole footwear and a voltage from a surface of 10-20 volts to earth may not even be felt if you touch it.
Immersed in water is one of worst case electrocution hazards, drive all the ground rods you want, the water is generally going to be earth potential. If your grounded service conductor (neutral) has voltage drop of 2 volts on it, that means it and all the equipment grounding conductors that land on it have a rise in voltage of 2 volts above earth voltage. If you have a MGN for the medium volt distribution some the voltage could be coming from voltage drop on that system, all the grounded conductors are bonded together and grounded conductor basically the same potential across all the systems involved. You will feel that 2 volts to earth if you are in the water. might not even need to touch the dock, there very well might be voltage gradients in the water surrounding any conductive portions of the dock that are in contact with the water.
GFCI and GFPE does not protect against such a rise in voltage on the EGC and electrocutions still happen at docks even if everything was done in accordance with NEC. Best advice is keep people out of the water in dock areas with electric power on them and keep electrical items as minimal as possible on them as well. Unfortunately if it is a metallic dock, it will end up being bonded to the EGC of the feed coming to it. This puts it at neutral to earth voltage of the service even if the feeder circuit is opened.
I don't have the neutral and ground bonded at the dock or house though. The only point on the property that is NG bonded is at the meter base. I understand voltage gradients, we call it step potential...same idea. I agree with water being at earth potential, thats why the dock frame, ladder, walkway etc is all bonded together and also at earth potential via ground rod at top of walkway. What i wasn't clear on was the lack of the grounding bar in the panel at the top of the walkway being tied to the ground rod also.
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