Connection at house Main & "dock" sub-panels?

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  #1  
Old 03-20-07, 12:59 PM
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Connection at house Main & "dock" sub-panels?

Getting ready to make the physical connections of the cable I ran last fall before it got too cold out. Now I need to connect a 55amp UFC 6/3 cable to the house main panel, and connect the other end to a sub-panel placed at the dock with shutoff breakers there as well. The other componemts of the dock i.e. boatlift, shorepower, lights, outlets, etc. will be fed off the sub.

Two parts I need answers on:

1) At the house panel I want a 50amp breaker. Since it's going to a dock sub, does it need to be a GFCI type breaker, or a standard one? There's definitely a $$ difference between the two.

2) For the sub-panel located at the land end of the dock is it, or is it not necessary for me to drive a brass pipe into the ground at or near the bulkhead for a copper wire form the grounding bar in the sub?

I'm ready to connect and need to be sure of these two points to walk away comfortable.
 
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  #2  
Old 03-20-07, 01:51 PM
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> Since it's going to a dock sub, does it need to be a GFCI type breaker

The panel may be fed with either a GFCI or a standard breaker. If you use a GFCI breaker to feed the subpanel, all circuits in the sub will have GFCI protection which would save you from purchasing individual GFCI breakers for dockside equipment. However, this means a trip would mean everything at the dock loses power plus a long walk to reset. Any outdoor general-purpose receptacles need GFCI protection, and I believe the boat lift requires GFCI protection, but lighting does not; I don't know about the shore power receptacle.

> drive a brass pipe into the ground at or near the bulkhead

You need to drive a 5/8" x 8' copper-clad ground rod near the subpanel and connect it to the subpanel ground bus using #6 copper wire and an acorn clamp on the rod.
 
  #3  
Old 03-20-07, 01:51 PM
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Ive been looking. I would install the ground rod.

Gfci Main.. Don't bother, one false trip and it's a long walk.

If you want to gfci at the sub.. well thats your call. Your other ckts will be GFCI protected. So price out 1-50A 2-pole or several single pole GFCIs. it may work out the same. Now you look t convieniance.

Your boat lift if 120V will need a GFCI, as well as the other obvious ckts.
 
  #4  
Old 03-20-07, 02:18 PM
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So it sounds like a choice between one primary GFCI at the main, or individual ones at the sub. Is this correct?

My lift will be 240v and I have a GEM remote control unit that says it has internal GFCI built in for the lift.

Where I place an outlet, if I have a GFCI receptical then I don't need a GFCI breaker, correct?

For items that are hard wired in like a pole light, I then do not need a GFCI breaker either, correct? Or is it safer to have regardless?

My shore power "tower" has individual breakers for each plug, so I susepct it doens't need a GFCI either????
 
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Old 03-20-07, 02:20 PM
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You will need two 2-pole breakers. One in the main panel and one at the sub.

If you run rec down the peir I would use a breaker. Protect the cable.
 
  #6  
Old 03-20-07, 02:26 PM
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> So it sounds like a choice between one primary GFCI at the main, or
> individual ones at the sub. Is this correct?

Correct. There is one more disadvantage to a GFCI main that I forgot to mention. It will trip if the sum of all leakage currents on branch currents plus the subpanel feeder exceeds 5mA. This means that minuscule leakages in two or three circuits could cause false trips when there is no real danger of electrocution. I think I just talked myself out of recommending a GFCI main. :-)

> My lift will be 240v...internal GFCI built in for the lift

No additional GFCI breaker needed.

> if I have a GFCI receptical then I don't need a GFCI breaker, correct?

Correct, a GFCI receptacle with properly wired LOAD side provides protection to all downstream wiring and outlets.

> For items that are hard wired in like a pole light, I then do not need
> a GFCI breaker either, correct? Or is it safer to have regardless?

No GFCI is required for lightning. It may even be unwanted since false trips could leave you in the dark in a possibly unsafe situation out on the dock.

> My shore power "tower" has individual breakers for each plug

I don't have any experience with boat shore power, so I cannot say with confidence if GFCI protection is required or not; perhaps someone else can give a definitive answer.
 

Last edited by ibpooks; 03-20-07 at 02:29 PM. Reason: clarity
  #7  
Old 03-21-07, 02:24 PM
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Great, I think Ive got a clear picture as to what I want/need to do. Thanks for the insight.
 
  #8  
Old 03-23-07, 11:07 AM
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FYI

You can Use a 60 amp feeder breaker at the house panel.

The only GFCI protection you need is for 120v receptacles.
 
  #9  
Old 04-05-07, 09:32 AM
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On the ground rod from the sub on the dock, can I use a standard copper water-line pipe (got lots of it laying around) driven in as the ground rod, or does it have to be the solid copper-clad type?
 
  #10  
Old 04-05-07, 10:06 AM
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According to 250.52(A)(5)(a), you may use 3/4" (or larger) copper pipe as an electrode; 1/2" copper pipe is too small. As always, the electrode must be driven at least 8 feet into the ground.
 
  #11  
Old 04-11-07, 08:29 PM
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Great I've got a few long pieces of 3/4" copper piping. Out of curiosity, why does it have to be 8' or more vice 4 or 6 foot?
 
  #12  
Old 04-11-07, 08:47 PM
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The 8' length is to ensure that the rod reaches consistently wet soil. Obviously in your case the soil is going to be wet much shallower than 8' as you are on a beach, but the code making panel decided that 8' was the minimum depth so that's what it must be.
 
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