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#162502 - 04/20/07 08:41 AM Shore Power
TwinCitySparky Offline
Member

Registered: 03/23/06
Posts: 52
Loc: Minnesota
The scenario: My sisters new lake house needs to have its dock mounted power pedestal placed/connected. The brother (me) was asked to do this simple project. The previous home owner had given them his complete set-up for this. There is a pedestal mounted disconnect with 240 30 amp plug-in point at shoreline - 100 feet of SO cord with twist-locks for connecting between the marine grade dock power pedestal and shoreline power. I understand you cant protect this whole thing with GFI protection without nuisance tripping. I simply don't feel comfortable running 100 feet of SO cord zip tied (suggested method) for 100' along a dock. They have a 4 year old daughter who is very inquisitive... I want to say sorry I dont feel comfortable connecting this but, I know the handyman will be next in line to do it.
Any suggestions? Money is not an issue with them. I was thinking (if I do it) that I could possibly protect the SO cord with PVC along the dock without gluing it so the whole thing could be dis-assembled before dock removal in the fall.

Thanks John

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#162515 - 04/20/07 10:47 AM Re: Shore Power [Re: TwinCitySparky]
ghost307 Offline
Member

Registered: 05/09/05
Posts: 884
Loc: Chicago Illinois USA
Mount some lengths of PVC, not connected together, as a route for the SO cord.
That way you can run the cord through the pipe and most of it will be concealed from the view of the kiddie.
You're not using the PVC as a raceway so much as using it as a support for the cord.
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#162516 - 04/20/07 11:28 AM Re: Shore Power [Re: ghost307]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6804
Loc: Brick, NJ USA
Twin City Sparky:
The east coast way (NJ) is to 'hang' the SO at the side of the dock, with 'slack'. As it is out of site, it should be OK. I've seen PVC cable hooks screwed to the beams, the cable laid-in and done. BTW, not a lake, but bay, river, & lagoon tidal waters.

John
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#162549 - 04/20/07 10:39 PM Re: Shore Power [Re: HotLine1]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
I am not sure why you say this can't be GFCI.
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#162556 - 04/21/07 06:15 AM Re: Shore Power [Re: TwinCitySparky]
TwinCitySparky Offline
Member

Registered: 03/23/06
Posts: 52
Loc: Minnesota
Portable SO cord has a certain amount of capitance leakeage to ground. I've read that 100ft of SO cord alone can leak the 5 milliamps to ground resulting in a false trip... John

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#162592 - 04/21/07 08:38 PM Re: Shore Power [Re: TwinCitySparky]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
I would say if there is that much leakage it is not safe for the application.
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#162598 - 04/22/07 02:22 AM Re: Shore Power [Re: gfretwell]
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
With any long run, even with good wire, capacitive coupling between the circuit conductors and the EGC or steel raceway may become an issue.

If it was up to me I would not GFCI protect this feeder to the pedestal. IMHO it is never a good design to GFCI protect a feeder.

I would make sure my ground fault path back to the source was as reliable as I could possibly make it.
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Construction & Maintenance Electrician
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#162603 - 04/22/07 07:00 AM Re: Shore Power [Re: TwinCitySparky]
TwinCitySparky Offline
Member

Registered: 03/23/06
Posts: 52
Loc: Minnesota
No GFI used. I ran PVC along the top outer edge of the dock. replaced all cord ends, checked all connections. Looks nice and safe - sister and hubby are happy! Thanks everyone for the replies.

John

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#162607 - 04/22/07 08:25 AM Re: Shore Power [Re: TwinCitySparky]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
This "coupling" BS is just a way to rationalize water in boxes and other real ground faults. If 100' of wire couples enough to trip GFCI I would have them tripping all over my house.
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#162609 - 04/22/07 08:54 AM Re: Shore Power [Re: gfretwell]
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
 Originally Posted By: gfretwell
This "coupling" BS is just a way to rationalize water in boxes and other real ground faults.


BS? \:\/

Greg it is not BS, it is a real issue.

As a an example when you wire a line isolation monitoring panel you should not even use THHN/THWN at all as its dielectric strength is to low.

Now I fully understand that LIMs are more sensitive to this than a GFCI but the cause and theory are the same.

Now instead of the LIM take a less sensitive class A GFCI and run a couple hundred feet of circuits on the load side of it and you may have a real problem.

If you are interested in some more info read the linked article.

Impedance of Wiring on Hospital Isolated Power Systems used in Operating Rooms

Another example of capacitance coupling can be observed when testing the continuity of long cable runs with a good meter. You will get an ohms reading until the cable (capacitor) charges.



Edited by iwire (04/22/07 08:58 AM)
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Construction & Maintenance Electrician
Massachusetts

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