Dock Power

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TwinCitySparky

TwinCitySparky

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Minnesota
So - I've got some existing dock power installs that need attention. One install has the typical DIY set-up: 20 Amp GFI at shoreline feeds across about 100' of dock to end of dock outlet/boat slip that is experiencing nuisance GFI tripping. I know most GFI manufacturers specify about 100' as max circuit length. Most installations that I've looked at have a power pedestal mounted at the point of use with GFI (on the dock over water next to boat) to minimize these issues. These installs typically have the 30 amp disconnect (no GFI) at shoreline that?s feeds a cord connected SO cable feeding to end of dock Receptacle. For some reason this set-up does not sit right with me. :roll: So - I'm thinking would it not be better to place GFI protection at shoreline disco and feed out to pedestal from load side into another GFI in pedestal? Or is the "capacitive coupling trip issue" additive as you feed from one GFI to the next? Would it not be cancelled as you pass thru each GFI? I'm basically just trying to create one long, safe nuisance trip free GFI circuit. Thanks
 
Sounds like you need to eliminate to shore-line GFCI.
Before doing so, I'd run a megger test to assure to safety on your circuit to the pedestal. If this is a dock associted with a family dwelling, Art 555 does not apply, but I personally would look to it as guidance.
 
Thank you for the reply. Yes - Eliminate "to shoreline" GFI would be easiest. That is the standard practice. One of these installs does involve a family, kids swimming under dock etc. It just floors me that we are held to such strict standards when placing an outlet anywhere close to a bit of water but, want to run some power over a lake on a steel framed dock? Go for it. Toss in a non GFI'ed 240 30 amp with an SO cord circuit and forget about it. Is there no better alternative other than treating it as a full blown art 555 install? (It is residential)

That is why I asked about the +100' capacitive coupling trip issue that every standard GFI oulet exhibits. Instead of one long troublesome GFI circuit, would this not be one of the times that it would make sense to "daisy chain" a couple GFI's to span this distance from shoreline all the way into the boat (Load from one to line of the other?) Therefore hopefully avoiding the one long "nuisance trip prone" circuit??? I suppose I could just try it.

Am I the only guy in the land of 10,000 lakes that thinks about this? (They say 10,000 but its more like 11,842) I guess that doesn't roll off the tongue as well :grin: I'm clear as mud again I suppose.
 
I totally agree with your concern an was in hopes we would both get some better ideas. If the dock is wired in "SO", I do think I woiuld follow Art 555's requiremnt for sleeving where exposed to being rubbed even though as a "resi" it's not required.
 
TwinCitySparky said:
Instead of one long troublesome GFI circuit, would this not be one of the times that it would make sense to "daisy chain" a couple GFI's to span this distance from shoreline all the way into the boat (Load from one to line of the other?) Therefore hopefully avoiding the one long "nuisance trip prone" circuit??? I suppose I could just try it.
Click to expand...

Daisy chaining GFCIs does not break the string into smaller lengths. The first GFCI will see the entire length as one long continuous circuit.
 
augie47
I totally agree with your concern an was in hopes we would both get some better ideas. If the dock is wired in "SO", I do think I woiuld follow Art 555's requiremnt for sleeving where exposed to being rubbed even though as a "resi" it's not required.
Today 08:26 AM
I appreciate it. Definetly will be in PVC where areas of damage are probable.

jim dungar Quote:
Daisy chaining GFCIs does not break the string into smaller lengths. The first GFCI will see the entire length as one long continuous circuit.
Today 08:57 AM

So you conclude the first GFI will "see and respond to" the next following GFI's load side? I was thinking/hoping the 2nd GFI would isolate the first one in line from what it sees on its load end. Guess it's just one of those things... I believe you, but think I might do a quick bench test to see it for myself. ;) Thank you!
 
TwinCitySparky said:
So - I've got some existing dock power installs that need attention. One install has the typical DIY set-up: 20 Amp GFI at shoreline feeds across about 100' of dock to end of dock outlet/boat slip that is experiencing nuisance GFI tripping. I know most GFI manufacturers specify about 100' as max circuit length. Most installations that I've looked at have a power pedestal mounted at the point of use with GFI (on the dock over water next to boat) to minimize these issues. These installs typically have the 30 amp disconnect (no GFI) at shoreline that?s feeds a cord connected SO cable feeding to end of dock Receptacle. For some reason this set-up does not sit right with me. :roll: So - I'm thinking would it not be better to place GFI protection at shoreline disco and feed out to pedestal from load side into another GFI in pedestal? Or is the "capacitive coupling trip issue" additive as you feed from one GFI to the next? Would it not be cancelled as you pass thru each GFI? I'm basically just trying to create one long, safe nuisance trip free GFI circuit. Thanks
Click to expand...

you're gonna have nuisance tripping with a long 120 volt
branch circuit, in my experience.
that's why nobody does it. if you use a 2pole GFI, and feed
the dock box with 240, it's gonna be your least troublesome solution.
you'll still have 120v. gfci's in the dock box as well. if the 2pole gfci
nuisance trips, rip the whole thing out an put a honda generator on
the end of the dock... :wink: obviously, don't have any other conductors
in the same raceway with the feeders for the dock box.

i worked on one dock box that the boat connected to it was pulling about
8 amps on a 220 volt non gfi protected circuit, and that was going thru the
aluminum hull of the boat (65' chris craft) and being dissipated in the surrounding
water.... aside from the wasted power, and shock hazard, it was eating up all
the zincs on every boat within a couple hundred feet. that was why they
called for service.... guy lost all his zincs, and a prop in two weeks.

the chris craft? shoulda renamed her "cathode". the owner refused to repair
the craft, and the marina mangement had me disconnect power to his pedestal.
then they caught him out there with a flashlight, at night, trying
to rehook the box..... then run a 30 amp cord up the dock to the next box....
then..... sigh.

boat people are a pain. they don't have any money, and piracy on the low
seas is always a problem.
 
Makes sense. The 2 pole "first in line" GFI will have the higher trip threshhold point. That will most likely be the solution with one of my jobs that has 240 to the dock. The other job with the 120V feed from house will be another deal.

Thanks.
 
Try an EG rated GFI breaker

Try an EG rated GFI breaker

Up here at teh lake, we see a lot of tripping due to the anode. We install an EG rated breaker (30 ma GFI trip) at the panel. we do the same for roof heat tape.
 
The article in the NFPA 70 just touches docks and marinas, there is another code book on just on docks. Its like the article 760 on FA in the NEC, but there is a whole different book that gets more in depth.
If the SO is run through the water out to the first pedestal I do believe (personal experience) there is only a couple that are approved for laying directly in the water. If my memory serves me, We used an SO style cord with MSHA ratings on it. I think it had 4 number six conductors in it. The pedestals we used were around 400 a piece and the had a couple 20A gfi, and couple 30A twist locks. J
Sorry if I cant remember better but this job was 5 years ago.

I really wish I carried a camera at the time, the romex running the gas pump was a keeper.
 
augie47 said:
I totally agree with your concern an was in hopes we would both get some better ideas. If the dock is wired in "SO", I do think I woiuld follow Art 555's requiremnt for sleeving where exposed to being rubbed even though as a "resi" it's not required.
Click to expand...

Some docks are built with a wireway built into the middle of the dock with a removeable cover and not subject to any damage when designed correctly. The floating docks rise up and down with the tide. I dont remember what cord was used in a big public dock I did in the late 80s but it was specked on the prints and it was an so type cord.
 
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