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Old 05-27-2009, 08:38 PM   #1
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Help! Conflicting info on sub panel feeder


I posted about a year ago and due to family medical issues the project was delayed until now.

Is 30A sub-panel enough?

To summarize, I decided to upgrade to a 60A feeder. The length is 250' from my 200A main to the boat house. This is a fixed (non floating) boathouse. According to Stubbie's excellent pictorial and the various threads I've read here, in 2008 the code changed requiring a 4 wire feeder. I called the local building department and the inspector said no, install a 3 wire from the main to the sub and then an equip ground from the sub to two ground rods on the shore. The electrician I contacted wants to run mobile home feeder cable (4 wires) in conduit but doesn't want to connect the 4th wire (ground) per the inspector's recommendation. He says in his x number of years doing these installs he's done all of them this way and the inspector always passes them. He also wants to install the ground rods under the pier walkway which will be submerged in water??

So, my question is, why are they insisting on 3 wire? I'm going to finish the install myself as the subpanel location (a utility room on the boat house that I'm building won't be ready), so do I ignore them and connect the ground between main and sub? The electrician says they do this to keep any water lightning strikes from going back to the main along the ground wire. Seems wrong to me as lightning will find its way back along any conductor. Also, is there a problem burying the ground rods in water? Seems corrosion will be an issue.

I need some expert guidance, please!

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Old 05-27-2009, 08:49 PM   #2
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Help! Conflicting info on sub panel feeder


If a ground is run it MUST be used. Period, end of story. Tell your electrician and his inspector to read NEC 250.32.
In fact, if you are under the 2008 NEC it is mandatory to have a dedicated equipment ground run with the feeder.
If your guy is not doing this, or willing to do this, I'd find another.

The ground rod under water is fine, as long as it is completely driven flush or deeper.

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Old 05-27-2009, 09:02 PM   #3
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Help! Conflicting info on sub panel feeder


Thanks Speedy...I was hoping you and/or Stubbie would chime in.

He is running the ground as it is included with whatever mobile home feeder wire is. I'm not familiar with that type of bundle, but he insists it is the proper size (for 60A at 250'). So, I will connect the ground at the Main and the Sub. I assume at that point, I make sure the Neutral and Ground busses are not bonded together?

So, in summary....

2 Hot, 1 Neutral, 1 Gnd from Main to Sub
No bonded Gnd and Neutral at Sub
1 Gnd from Sub to ground rods

I'll use a GFI breaker at the Main. Should I use a Main Lug sub or for convenience a Main breaker style sub? If the latter, does that have to be a GFI style breaker since it is protected upstream by a GFI in the main?

EDIT: OKay, so I googled mobile home feeder. Looks like he's running 2-2-2-4 AL which should be fine for 60A at 250'. I am burying it in conduit for extra protection. Suprisingly the electrician said he could get that cheaper than anything else, even standard THHN/THWN.

Last edited by robertmee; 05-27-2009 at 09:07 PM.
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Old 05-27-2009, 09:35 PM   #4
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Help! Conflicting info on sub panel feeder


Looks good to me. You do not need a GFI breaker at the sub if you are using one at the main. You do not need to GFI protect the whole feeder, but you can if you want.
You do need a disconnect at the detached structure so a main breaker is usually easiest.
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Old 05-27-2009, 09:42 PM   #5
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Help! Conflicting info on sub panel feeder


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Looks good to me. You do not need a GFI breaker at the sub if you are using one at the main. You do not need to GFI protect the whole feeder, but you can if you want.
You do need a disconnect at the detached structure so a main breaker is usually easiest.
Thanks!
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Old 05-27-2009, 10:40 PM   #6
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Help! Conflicting info on sub panel feeder


Unfortunately it sounds like you have only the inspectors way and the electricians way to run electrical to your fixed dock. This is rather unusual as almost all lakes where I have experience have a detailed guide to dock wiring available at the jurisdictions code department for use by installing contractors and electricians. Your in kind of a rock and a hard spot.... so to speak.

Do not do as the inspector says and you risk being failed on the installation. Hard choice not sure what to tell you but I do not agree with what they are saying.

In my area for a dock feeder.... 4 wire is mandatory, copper is mandatory, all conductors including the ground must be insulated and must be in pvc conduit. Some lake jurisdictions here require gfci protected feeders but a few don't care. Basically everything on the dock needs gfci.

If the inspector used 'equipment ground' as his term for the conductor to the ground rods I question his understanding of its purpose. That conductor is a grounding electrode conductor not an equipment ground and has nothing to do with the equipment grounds of the branch circuits at the sub-panel.

If all else fails I would do the 4 wire with equipment ground not connected as the electrician wants then after passing the installation connect it as 4 wire and unbond the sub. neutral bar. Add the equipment ground bar then connect the feeder equipment ground and branch circuit grounds to it and the GEC to the ground rods. Why the electrician wants to bury the ground rods below water stumps me but each to their own. His explaination about the lightning traveling the ground back to the main as being wrong and not wanted is ridiculous...this is exactly what you want to utilize the grounding electrode system to put the high amperage to earth and protect your property. Besides It would travel the feeder neutral anyway in a 3 wire system and for that matter it may travel all the feeder conductors. I hate bs explanations like you got.
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Old 05-28-2009, 11:18 AM   #7
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Help! Conflicting info on sub panel feeder


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Unfortunately it sounds like you have only the inspectors way and the electricians way to run electrical to your fixed dock. This is rather unusual as almost all lakes where I have experience have a detailed guide to dock wiring available at the jurisdictions code department for use by installing contractors and electricians. Your in kind of a rock and a hard spot.... so to speak.

Do not do as the inspector says and you risk being failed on the installation. Hard choice not sure what to tell you but I do not agree with what they are saying.

In my area for a dock feeder.... 4 wire is mandatory, copper is mandatory, all conductors including the ground must be insulated and must be in pvc conduit. Some lake jurisdictions here require gfci protected feeders but a few don't care. Basically everything on the dock needs gfci.

If the inspector used 'equipment ground' as his term for the conductor to the ground rods I question his understanding of its purpose. That conductor is a grounding electrode conductor not an equipment ground and has nothing to do with the equipment grounds of the branch circuits at the sub-panel.

If all else fails I would do the 4 wire with equipment ground not connected as the electrician wants then after passing the installation connect it as 4 wire and unbond the sub. neutral bar. Add the equipment ground bar then connect the feeder equipment ground and branch circuit grounds to it and the GEC to the ground rods. Why the electrician wants to bury the ground rods below water stumps me but each to their own. His explaination about the lightning traveling the ground back to the main as being wrong and not wanted is ridiculous...this is exactly what you want to utilize the grounding electrode system to put the high amperage to earth and protect your property. Besides It would travel the feeder neutral anyway in a 3 wire system and for that matter it may travel all the feeder conductors. I hate bs explanations like you got.
Good post.
I had a similar situation with a boat house. More like a cabana, because it's on land near the water. The inspector told me to run the 4 wire feeder, but NO ground rod, period. When I questioned him on this, he told me that AHJ has the final word, and if I drove a rod he would fail the inspection. He had issues with stray currents around the lake and even referenced a death. So, no ground rod. I still sometimes want to go back out there and drive one.
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Old 05-29-2009, 08:16 PM   #8
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Help! Conflicting info on sub panel feeder


I layed it all out, spelled it out explicitly based on your guys info and I still did not get what I wanted. I drove the 3 hour round trip to day to inspect the work and here is what I found:

4 wire in conduit. Two Hots, Neutral and Ground from Main Panel to Sub. No extra ground and no ground rods. I called them on it and they said that the inspector told them that if they were running a 4-wire like I asked for, then isolate the neutral and ground in the sub, connect the two hots and I wouldn't need the ground rods. They are saying either 3-wire with a ground rod on shore, or 4-wire back to the main, but not both. So now what? I guess I'll be wading in the muck and installing my own ground rod and extra ground at the risk of pissing off the inspector, or is it safe and OK the way it is????? If it matters, the boat house is 100' off shore. BTW, another argument I kept hearing is that a boathouse is treated like a garage as far as the NEC is concerned and nobody installs an extra ground rod for a garage.
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Old 05-29-2009, 08:24 PM   #9
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Help! Conflicting info on sub panel feeder


The boat house is in/on the water?
Or on a small island?
I think you are stuck doing what the Inspector wants

If a detached building here we are required to run ground rods
I had to run them for my detached pool cabana
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Old 05-29-2009, 08:42 PM   #10
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Help! Conflicting info on sub panel feeder


Quote:
Originally Posted by robertmee View Post
BTW, another argument I kept hearing is that a boathouse is treated like a garage as far as the NEC is concerned and nobody installs an extra ground rod for a garage.
The code does NOT differentiate beteween garages, sheds, boat houses, or outhouses.

What town is this? Dumbsh*tville?

Where do they find these inspectors and contractors? Do they even own code books???
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Old 05-30-2009, 11:15 AM   #11
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Help! Conflicting info on sub panel feeder


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The code does NOT differentiate beteween garages, sheds, boat houses, or outhouses.

What town is this? Dumbsh*tville?

Where do they find these inspectors and contractors? Do they even own code books???
I'm beginning to wonder....So, I assume that I MUST install the ground rods myself and that the current install is unsafe? I'm not asking these guys back out.
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Old 05-30-2009, 11:43 AM   #12
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Help! Conflicting info on sub panel feeder


The ground rod or rods is a requirement from the NEC. But, as you can see inspectors have a different take on things. The cabana where I installed the sub panel has no ground rod. And that is only because the AHJ would not allow it.
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Old 05-31-2009, 08:13 PM   #13
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Help! Conflicting info on sub panel feeder


I found all the relevant sections in the new 2008 code, so caution to the wind, I'm going to wire it like it should be. I'll argue with the inspector later

Given that, can I run a #6 insulated ground wire exposed and underneath the pier walkway? I'll use the same hangers that the water and electrical conduits are hanging on. Also, anything to be wary of in the transistion of the pier down to the ground for the rods? Can I sink one ground rod just under the pier so the wire isn't exposed to lawnmower hazards and be done with it?
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Old 05-31-2009, 10:11 PM   #14
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Help! Conflicting info on sub panel feeder


Are you talking about the bonding conductor for the metal on the boat dock? If so yes you can do that on a fixed dock. but it doesn't have to be a #6 a #8 is fine.
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Old 06-01-2009, 09:45 AM   #15
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Help! Conflicting info on sub panel feeder


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Are you talking about the bonding conductor for the metal on the boat dock? If so yes you can do that on a fixed dock. but it doesn't have to be a #6 a #8 is fine.
I'm talking about the Ground wire from the Sub panel back to the Ground Rods. The dock is all wood if that makes any difference. The only metal is the exterior door on the storage shed area (door skin, hinges, knob).

Well, check that....I do have four lifts that are galvanized steel. Two boat hoists and two manual crank jetski lifts. The lift motors on the hoists are wired to GFIs. The hoists themselves are suspended via cables, pullys and a steel winding pipe. Do I need a seperate ground for that equipment other than the GFI electrical connection? The Jetski lifts mount to the wooden dock but do have a support member that sinks into the lake bed two feet so it is essentially grounded by default, no?

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