# Ideal dock wiring Questions?

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• 03-29-2011, 10:55 AM
jwelectric
Randy

Voltage drop is a reality but it does nothing to make a grounding path less efficient. The only thing that voltage drop will do is hasten the tripping of a breaker by increasing the amount of current draw to the load. On a fault the low resistance of an equipment grounding conductor will work just as well no matter how far it is pulled.
A thousand feet of #12 copper conductor will have a resistance of 1.9 ohms and at 120 volts in a fault condition will draw 63 amps.
Using the numbers given for a driven rod with earth as the return path as outlined in 250.56 of 25 ohms and I promise this low number will be hard to get the current draw of a fault will be 4.8 amps. The math shows that even at 1000 feet the equipment grounding conductor wins hands down.

I am sure in my heart that you without a doubt excel in your chosen field of plumbing but you display a lack of knowledge of earth grounding and its purpose. What I have said throughout this thread I have backed completely with code sections and math. Unless all those master electricians can do the same I will agree with you that they don’t know diddly.
• 03-29-2011, 10:56 AM
jwelectric
deleted as my computer seems to like posting everything twice
• 03-29-2011, 11:06 AM
ballvalve
Actually a big hamster cage buried and bonded near the dock might work as a EP Grounding grid. Or a section of the mayors chain link fence.

And as for that vent thats flooding your yard, just install a trap upside down, or cut some slots in the vent pipe and put a coffee can over it. It will dress up that standing seam roof.

As for docks, someone should make them of injection molded plastic and deck them with the milk carton 2x6's. Get all the metal out.

Finally, indeed there are all to many poor people that absolutely cannot afford a plumber or electrician, and their homes look like the three stooges on drugs built them.

In rehabbing and remodeling, I am constantly amazed how FEW people are electrocuted by their crazy work.
• 03-29-2011, 12:07 PM
jwelectric
Private docks

What section of the National Electrical Code would one use to make the electrical installations for a private dock or pier?

Article 555 covers the installation of wiring and equipment in the areas comprising fixed or floating piers, wharves, docks, and other areas in marinas, boatyards, boat basins, boathouses, yacht clubs, boat condominiums, docking facilities associated with residential condominiums, any multiple docking facility, or similar occupancies, and facilities that are used, or intended for use, for the purpose of repair, berthing, launching, storage, or fueling of small craft and the moorage of floating buildings.
What Article 555 does not cover are private, noncommercial docking facilities constructed or occupied for the use of the owner or residents of the associated single-family dwelling

Then what section of the NEC would one use?
ARTICLE 682 Natural and Artificially Made Bodies of Water

In this article we are told that the electrical installations must follow;
682.3 Other Articles. Wiring and equipment in or adjacent to natural or artificially made bodies of water shall comply with the applicable provisions of other articles of this Code, except as modified by this article. If the water is subject to boat traffic, the wiring shall comply with 555.13(B).

If this dock is subject to boats then there are some pretty stringent rules that must be followed. For the branch circuit wiring to lights and receptacles on this dock we are sent back to 555.13(B)

(B) Installation.
(2) Outside Branch Circuits and Feeders. Outside branch circuits and feeders shall comply with Article 225 except that clearances for overhead wiring in portions of the yard other than those described in 555.13(B)(1) shall not be less than 5.49 m (18 ft) above grade.
(5) Where cables pass through structural members, they shall be protected against chafing by a permanently installed oversized sleeve of nonmetallic material.
(5) Protection. Rigid metal or nonmetallic conduit suitable for the location shall be installed to protect wiring above decks of piers and landing stages and below the enclosure that it serves. The conduit shall be connected to the enclosure by full standard threads. The use of special fittings of nonmetallic material to provide a threaded connection into enclosures on rigid nonmetallic conduit, employing joint design as recommended by the conduit manufacturer, for attachment of the fitting to the conduit shall be acceptable, provided the equipment and method of attachment are approved and the assembly meets the requirements of installation in damp or wet locations as applicable.

Article 225 addresses outside feeder and branch circuits with Part II addressing a separate building or structure.
225.31 Disconnecting Means. Means shall be provided for disconnecting all ungrounded conductors that supply or pass through the building or structure.

225.36 Suitable for Service Equipment. The disconnecting means specified in 225.31 shall be suitable for use as service equipment.
Exception: For garages and outbuildings on residential property, a snap switch or a set of 3-way or 4-way snap switches shall be permitted as the disconnecting means.

What about a grounding electrode system? This requirement will be found in Part II of 250
250.32 Buildings or Structures Supplied by a Feeder(s)
or Branch Circuit(s).
(A) Grounding Electrode. Building(s) or structure(s) supplied by feeder(s) or branch circuit(s) shall have a grounding electrode or grounding electrode system installed in accordance with Part III of Article 250. The grounding electrode conductor(s) shall be connected in accordance with 250.32(B) or (C). Where there is no existing grounding electrode, the grounding electrode(s) required in 250.50 shall be installed.
Exception: A grounding electrode shall not be required where only a single branch circuit, including a multiwire branch circuit, supplies the building or structure and the branch circuit includes an equipment grounding conductor for grounding the normally non–current-carrying metal parts of equipment.

It is through this exception that I made the comment that for a single branch circuit I would not install a rod at a pier.
(B) Grounded Systems. For a grounded system at the separate building or structure, an equipment grounding conductor as described in 250.118 shall be run with the supply conductors and be connected to the building or structure disconnecting means and to the grounding electrode(s). The equipment grounding conductor shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded. The equipment grounding conductor shall be sized in accordance with 250.122. Any installed grounded conductor shall not be connected to the equipment grounding conductor or to the grounding electrode(s).

The requirement not to connect the equipment grounding conductor to the grounded (neutral) conductor that the term “isolated from” comes into play. It does not mean to cut the equipment ground conductor and reconnect it to the ground rods.
The requirements for the equipment grounding conductor supplied with the branch circuit for a body or water found in Article 682 that modifies the requirement for equipment grounding found in Part II of 250

682.31 Equipment Grounding Conductors.
(A) Type. Equipment grounding conductors shall be insulated copper conductors sized in accordance with 250.122 but not smaller than 12 AWG.

The equipment grounding conductor installed with the branch circuit must be insulated and no smaller than #12. UF cable does not have an insulated equipment grounding conductor so the use of UF is disallowed.

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 panelboard.

The metal dock must be bonded to the equipment grounding conductor in the panel at the pier or dock and as outlined below this bonding must be done with a solid copper #8 conductor

The disconnect installed at the pier or dock must also have an equipotential plane shall be installed.
682.33 Equipotential Planes and Bonding of Equipotential Planes. An equipotential plane shall be installed where required in this section to mitigate step and touch voltages at electrical equipment.
(A) Areas Requiring Equipotential Planes. Equipotential planes shall be installed adjacent to all outdoor service equipment or disconnecting means that control equipment in or on water, that have a metallic enclosure and controls accessible to personnel, and that are likely to become energized.
The equipotential plane shall encompass the area around the equipment and shall extend from the area directly below the equipment out not less than 900 mm (36 in.) in all directions from which a person would be able to stand and come in contact with the equipment.
(C) Bonding. Equipotential planes shall be bonded to the electrical grounding system. The bonding conductor shall be solid copper, insulated, covered or bare, and not smaller than 8 AWG. Connections shall be made by exothermic welding or by listed pressure connectors or clamps that are labeled as being suitable for the purpose and are of stainless steel, brass, copper, or copper alloy.

Here is the proper way to install electrical circuits to a dock as outlined in this thread. To do anything less will result in an unsafe and dangerous installation.
Everything posted here is straight from the 2008 code cycle. It is not myth or fantasy nor would anything I think make it safer but the requirements straight from the rules governing the safety of persons and equipment.
• 03-29-2011, 02:15 PM
LOTW
The equipment grounding conductor installed with the branch circuit must be insulated and no smaller than #12. UF cable does not have an insulated equipment grounding conductor so the use of UF is disallowed.

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 panelboard.

The metal dock must be bonded to the equipment grounding conductor in the panel at the pier or dock and as outlined below this bonding must be done with a solid copper #8 conductor

JW, thank you for the specific quote from the NEC. Two questions re my contemplated single circuit to servie my boathouse. First, since UF cable is apparently not permitted, what cable should I use? Second, on a separate floating wooden dock about 50 feet from the boathouse I have a metal swim ladder. There will not be electricity brought to this separate floating dock. Should this ladder be bonded? Is bonding ever an issue when there is just a single circuit brought to the structure?
• 03-29-2011, 04:01 PM
jwelectric
If you are installing a single circuit to the boat house then a proper rated light switch that breaks the hot conductor(s) at least 5 feet from the high water line is all that you would need. I would install type THW conductors in schedule 40 PVC pipe no less than ¾ inches. No rods would be needed.

If the ladder and floating dock has no electrical circuits then no bonding would be required but let me caution you about boats with electricity on them in the area of the floating dock that could cause voltage gradients in the water.

And one thing I left out of my last post, all circuits of 60 amps and less must have GFCI protection.
• 03-30-2011, 08:51 AM
Randyj
I think we need a separate thread simply to discuss equipotential grounding planes. Every reference I've pulled up to get a description of EPG's refer to RFI. This is not an issue where radio frequencies are not an issue. I see none, other than your posts and quotes of NEC that refer to eliminating shock hazzards. They all seem to go into discussions of impedance and capacitance... things that affect radio frequencies. Too, it appears that the NEC quotations are not defining what is "equipment". The equipment ground appears to refer pretty much just to equipment housed in metal cabinets.
I would think that if there is not a ground rod at the entrance to the walkway then there is a huge safety issue when putting gas in a boat. A static charge or a difference in voltage/current due to the difference in the currents from that green wire running to a ground rod 700 ft away and the voltage/current in the dirt or water could result in enough of a spark to ignite the gasoline. Maybe it would be a separate issue but I see plenty of convenience outlets next to boat slips mainly for battery chargers. What does the NEC say about those? I would think the same rules/principles would apply that apply to outlets in kitchens.
BTW, I've got a stack of floats waiting for me to build my dock... so this discussion will make me capable of any electrical installations I want to do on that dock. Permits, unions, and licensing is a different subject. If we try to satisfy everybody and not step on any toes we'll hire laborers to load a water heater into a moving van driven by a CDL licensed driver, have another labor crew to unload and put it in place to be installed then hire carpenters to secure it in place, then hire electricians to hook up the electrical then a plumber to attach the water lines and call out a health inspector to make sure everything is not going to transmit some kind of disease and call in the EPA to assess the environmental impact... .we can get into OVER regulation.
Structurally, a metal dock with a metal roof is very similar to a hamster cage...
• 03-30-2011, 03:04 PM
jwelectric
check out thread named ground rods
• 03-30-2011, 08:29 PM
Randyj
I'll be sure to check out the ground rod thread.

Here's a question since we've about beat dock wiring / grounding to death... If a dock is grounded to comply with code then what's to prevent the same thing from happening as clipping the direct ground if there is a fault where the "hot" wire touches the ground wire anywhere else in the system? If it's not bonded to neutral at the switch box then it still goes into the earth and the same danger exists. It's like the same problem in reverse... with the same or worse dangers.
• 03-31-2011, 03:10 AM
jwelectric
When the equipment grounding conductor is cut there is no low resistance path back to the source. To clip the equipment grounding conductor and connect it to the ground rods puts a very big resistor in line with the fault current path.

With the equipment grounding conductor in place from the remote panel back to the service current will only have to overcome the resistance of the wire which will be around one ohm or less.
With no equipment grounding conductor in place but instead connected to earth then current will have to overcome a resistance that is very high and it can be into the thousands of ohms.

Using Ohm’s Law of current will be the resistance divided into the voltage. With a 120 volt circuit and a 1 ohm resistance conductor 120 amps of fault current can flow but with the resistance of earth the current can be as little as .1 amps. Which do you think will open the breaker?
Let’s be generous and use what is mandated by the NEC of 25 ohms on a ground rod. We still would not have but 4.8 amps of current flowing through earth searching for the source and again the breaker would not trip.

Just reading your post I am under the assumption that you somehow feel that current is flowing into earth and staying there. This is against the laws of physics. The current must return to its source and on our homes this is the transformer that supplies our homes.
• 03-31-2011, 06:00 AM
jwelectric
I think that a lot of the confusion about earth grounding of a premise wiring system such as our homes comes from the methods used for connecting an electrical component to an automotive system.

In the automotive system we have a 12 volt system that is powered by a 12 volt battery. This battery has two post one positive + and one negative -. We all call the negative terminal of the battery the ground terminal. If one was going to wire a light to this system we would take a hot wire + and place a fuse (overcurrent device) inline to a switch to control the light. Another wire would be connected to “ground” or the negative – terminal of the battery which is connected to the body of the automobile.
In the automobile the negative – side of the battery is “grounded” or connected to the frame of the automobile. In reality what we are really doing is connecting this “ground wire” to the negative terminal of the battery by using the metal path of the automobile as the negative wire. Just as with the rusty trailer hitch should this negative – path (the ground) be broken the light would not work. The current path back to the negative post of the battery would be broke and there would be no complete path for the current to follow.

In a premise wiring system such as our homes we can connect a light by installing a breaker (overcurrent device) to the bus bar of our panel and installing a conductor to a switch. From the switch to the light and then the other wire is connected to the neutral terminal bar in the panel. This terminal bar is connected back to the transformer through a neutral wire. Both of these circuits use only two wires in order to work, in the automobile a hot and a ground (negative) and in our home a hot and a neutral.

The major difference between the term used in an automotive circuit and the wiring system installed in our homes is the term “ground”. In the automobile the term “ground” is used to define the negative terminal of the battery. In our homes the term ground is used to define earth which an automobile does not have. Our negative wire (a bad use of the word negative) is the neutral wire.
In both cases the return path will carry current the negative (ground) wire in the automobile or the neutral of the house wiring. In both cases the current that leaves the source, in the automobile the battery and in our homes the transformer, returns to the source. No current is leaking out of the circuit into anything or being dumped through the grounding conductor to earth.

In the wiring systems installed in our homes we install a grounding electrode system which must be bonded to our service neutral. Then we install a third conductor called the equipment grounding conductor which is also bonded to the grounding electrode and the neutral conductor at our service.

Unlike the “ground wire” installed in our automobile which will be carrying current, the equipment grounding conductor, this third wire, will not carry any current at all unless there is a ground fault. The purpose of this grounding wire in the circuits of our home is in case a hot wire comes in contact with any exposed metal. This equipment grounding conductor will carry this faulted (hot touching the metal) current back to the neutral in the service equipment and back to the transformer causing a high draw of current that will open the overcurrent device. It would be just like taking the hot conductor in our automobile and touching the ground (body of the automobile) the current would be carried back to the negative of the battery causing a high current draw thus blowing the fuse.

As outlined in 250.4 of the NEC this earth grounding is done for four reasons and the opening of the overcurrent device is not one of them. Ground as defined by the NEC for the wiring systems installed in our homes is a connection to earth. Ground as defined in automotive wiring is defined as a connection to the negative post of the battery. There is a big difference between the two definitions. In our homes the second wire is called a neutral and the grounding is a connection to earth which an automobile does not have.

If earth grounding would work for a return path then the utility companies around America would not install the neutral conductor from the transformer to our homes, business, and industrial plants. There would be no need for this conductor and the utilities would save millions of dollars.
• 03-31-2011, 07:37 AM
Randyj
I'm good with discussing the theories of automotive electricity and comparing to utility company supplied power to it's customers. I'm also good with comparing the term "ground" in those cases. It appears to me that the term "ground" should be completely thrown out except to refer to a wire or circuit connected to the earth, dirt, ground... Seems the term introduces much confusion. So, a term should be used to describe the negative side of a DC circuit and another term or equivalent term to describe the neutral side of an AC circuit. In dual circuits such as 240 volt AC a similar delineation is made by saying L1 and L2. IMO, to compare a utility to an automobile is totally like discussing apples and oranges because the automobile is like a completely self contained utility and all of it's users/customers. Another big difference is that the modern automobile contains RF circuits, AC circuits, and DC completely self contained.. if compared to a dock that's like installing a gasoline engine powered generator on a dock rather than running electrical wires from a service panel hundreds of feet away... no more need for an earth ground than installing a ground rod to an automobile. It would then have it's own electrical source and the green wire would lead directly back to the generator without the earth contributing anything, no voltages, no currents, no resistance of earth. In common vernacular just about everyone uses the term "ground" for "neutral". In my posts I have tried to avoid this confusion. If we get particular about the correct use of the language then we should refer to it as a "neutral connection or neutral side of the circuit".. a short cut is to simply say "neutral (for continuous connection to the neutral of the transformer)" or "ground (for continuous connection to earth)". As a professional multi-skilled laborer I have to know the difference. A discussion of all the different professions encompassed in the field of maintenance should be a different thread (more apples and oranges). There is no doubt in my mind whatsoever that the NEC as well as all plumbing codes are totally devoted to safety and health. In medicine it is the field of preventive medicine (health inspector) (one of my previous occupations/Military) that is the first line of defense. Same as in buildings/structures/utilities.. it is the maintenance man who is the first line of defense.
Back to dock wiring.. Wouldn't it or would it not be... safest to simply NOT directly connect any earth ground at all to a metal dock? All earth ground wires terminate at receptacles. All wires in insulated (PVC) and all outlet & switch boxes be made of a non-conductive material? All switch box panels on the dock insulated from contact with the dock? .. .this would be comparable to how any appliance is wired, everything insulated from human contact and totally avoids any possibility of even a tickle voltage from the difference in stray voltages, voltage drops and any kind of electrical currents. It appears that this would certainly satisfy the NEC requirement that the green wire/ground be a continuous connection all the way back to the service entrance. No need for epg's, grids in the earth, buried hamster cages, ground rods... nothing except circuit wires to provide electricity and protection from faults. KISS... Keep it simple suckah. For one thing... wiring a dock is the big time equivalent of running an extension cord to the dock. You would not connect the ground wire of an extension cord to a dock or metal building....
• 03-31-2011, 08:50 AM
Randyj
Quote:

Originally Posted by jwelectric
WOW!!!!!!!!!!!!!!!!
I CAN’T BELIEVE MY EYES

Why haven’t I ever thought about doing this before?
........
Has anyone else tried this? What did you get?

I just got back in from trying this to verify once again what I've done several times before. It appears that my dirt is a very good conductor. I completely disconnected the wire from the ground rod the got out my walmart voltmeter to check the voltage between the "hot" wires in my switch box and the ground rod. I got a full 123 volts AC. I have done this at other places and got only 64 volts. If a hot wire hit the dirt around here it would trip the breaker. It is right at 200 ft to the transformer and it's ground rod.... of course, the ground is wet after all the rains we've had lately.... and the neutral wire is properly connected to the transformer unlike the time it got jerked out of the transformer when a limb fell across the line.
The nature of the dirt here is a bit different than other places. If you drag a strong magnet across the ground you pick up lots of rocks and dirt due to the high ferrous content.
• 03-31-2011, 09:47 AM
jwelectric
Quote:

Originally Posted by Randyj
IMO, to compare a utility to an automobile is totally like discussing apples and oranges because the automobile is like a completely self contained utility and all of it's users/customers. Another big difference is that the modern automobile contains RF circuits, AC circuits, and DC completely self contained.. if compared to a dock that's like installing a gasoline engine powered generator on a dock rather than running electrical wires from a service panel hundreds of feet away... no more need for an earth ground than installing a ground rod to an automobile.
In common vernacular just about everyone uses the term "ground" for "neutral". In my posts I have tried to avoid this confusion. If we get particular about the correct use of the language then we should refer to it as a "neutral connection or neutral side of the circuit".. a short cut is to simply say "neutral (for continuous connection to the neutral of the transformer)" or "ground (for continuous connection to earth)". As a professional multi-skilled laborer I have to know the difference.
Back to dock wiring.. Wouldn't it or would it not be... safest to simply NOT directly connect any earth ground at all to a metal dock? All earth ground wires terminate at receptacles. All wires in insulated (PVC) and all outlet & switch boxes be made of a non-conductive material? All switch box panels on the dock insulated from contact with the dock? .. .this would be comparable to how any appliance is wired, everything insulated from human contact and totally avoids any possibility of even a tickle voltage from the difference in stray voltages, voltage drops and any kind of electrical currents. It appears that this would certainly satisfy the NEC requirement that the green wire/ground be a continuous connection all the way back to the service entrance. No need for epg's, grids in the earth, buried hamster cages, ground rods... nothing except circuit wires to provide electricity and protection from faults. KISS... Keep it simple suckah. For one thing... wiring a dock is the big time equivalent of running an extension cord to the dock. You would not connect the ground wire of an extension cord to a dock or metal building....

As to the generator at the dock it would depend on the type of generator being used as to whether or not a grounding electrode system would be required. A self contained portable generator would not require a grounding electrode but a permanently installed generator would require a grounding electrode system.

There is no way on earth to make stray voltages disappear. It would require that there be no more electrical storms and both the north and south poles would have to be neutralized to stop all stray voltages or gradients voltages through earth’s crust. The temperature would need to be constant over the entire earth with no cold fronts colliding with warm fronts.
All theses combined causes the earth’s crust to have voltages without there ever being any type of electrical current produced by the utilities or any other man made current.

The thought of comparing the 12 volt DC system to a 120 volt AC system as being like comparing apples to oranges is untrue. The only two things that change are the type of voltages and the numbers. The equations are the same.

As to calling the neutral the ground conductor is not exactly correct either. The neutral conductors that supply our homes are a current carrying conductor just as the ungrounded (hot) conductors. In a 120 volt circuit the neutral carries just as much current as the hot conductor. The equipment grounding conductor never carries current unless something bad goes wrong.
The reason the neutral is called the groundED conductor is because the utility connects this conductor to earth. In most cases for a dwelling unit the return or neutral of the high voltage supplying the transformer is connected to the neutral of the secondary (the one coming to our homes) and to the grounding electrode conductor at the utility pole or pad mounted transformer. It is called groundED by the NEC because by the time the electrician gets to wire the building this earth connection is already established or past tense.

The electrician installs the equipment groundING conductor at the time of the installation therefore in the present tense. This grounding conductor is then bonded to the grounded conductor and the grounding electrode conductor at the service. The grounded neutral is earth grounded twice, once by the utility and again by the electrician at the service equipment and can be earth grounded for the third and more times each time the conductors leave the service equipment and go to another building or structure on the outside.
The purpose of bonding this metal dock to the grounding electrode for the panel supplying the metal dock is in case one of the circuits supplying equipment such as lights, receptacles, boat lifts, and the such on the metal dock should come into contact with the metal dock there would be a low impedance path back to the source supplying power to that dock in order to open the overcurrent device thus stopping the flow of current.
This bonding is not to relieve the voltage gradients between the water and the metal or wooden dock. A ground rod will not relieve this current. An equipotential grid does not relieve these stray voltages but instead brings everything to the same or equal potential therefore no current flow.

Even if everything was installed in non-metallic enclosures and raceways it would not relieve the stray voltages. There would still be the step potential between the water and the dry ground.
• 03-31-2011, 09:48 AM
jwelectric
Deleted as it was a duplicate
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