Marina Wiring and grounding

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220wire

Member
I am looking retrofit job on a concrete floating dock system. The engineer is asking that a stainless steel ground rods be used at each individual pedestal. He envisions the ground rod field bent (is that ok) and that they are partialy submerged in the salt water. I view this as a potential problem with stray voltages being capable of being carried all over the harbor now. I guess I shouldnt worry too much about the engineering aspect and just bid what is presented, but I would hate to have someone get hurt beacause of my installation. (see attached pic)
A couple more questions:
Should I also inquire about the POCO using an isolation transformer?
Is type W ok for submersion?
What are the best/quickest mechanical splices rated for submersion?
Are sub-panels ok to be on a floating dock?
The last two panels I installed had GFCI monitoring at the panels. Is this a requirement or just something that is a good idea?

Thanks in advance
 
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nakulak

Senior Member
that detail is interesting. did he specify any bonding for the steel plating ?
Sounds like a nice job. I've never used a SS ground rod, I wonder what they are going for.
 
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220wire

Member
I have read 555. 553.8 (D) seems to have a bit more information on my grounding question but doesn't say to use a ground rod at each pedestal. I wont mind "pounding" those in.
Nowhere have I found that type w is ok for submersion
And the way I read 553.4 it says no service equipment on the floating structure. I second guess myself but believe a sub-panal on a dock is service equipment.

Still looking for answers
 
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charlietuna

Senior Member
I have done a few dock installs but the pedistal is grounded by the bond in it's feeder. Ground rods out on a dock partially submerged in salt water is useless to me ?
 
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hardworkingstiff

Senior Member
Location
Wilmington, NC
220wire said:
...I guess I shouldnt worry too much about the engineering aspect and just bid what is presented...
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I don't think asking a question would be out of line. That grounding you showed sure seems like a waste to me. Maybe a phone call to the dock manufacturer to see what they've seen in the past.
A couple more questions:
Should I also inquire about the POCO using an isolation transformer?
Click to expand...
I've never seen it done, but it could cut down on the stray voltage issues.
Is type W ok for submersion?
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I'm of the understanding it is. Best to get written confirmation from the manufacturer of the cable you propose to use. I've installed it submerged and most of the times the cables under the gangway go under at high tides (twice a day).
What are the best/quickest mechanical splices rated for submersion?
Click to expand...
You might want to check 400.9 unless you are talking about when you hit the floating dock and making joints in that junction box in the concrete floating dock. The engineer I use signed off on butt splices with heat shrink.
Are sub-panels ok to be on a floating dock?
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Sub panels, yes, service equipment, no.
The last two panels I installed had GFCI monitoring at the panels. Is this a requirement or just something that is a good idea?
Click to expand...
Just a very good idea.
 
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hardworkingstiff

Senior Member
Location
Wilmington, NC
One other thing.

Everyone I know uses table 400.5(B) to size the "W" cable ampacities. Most people don't realize that 110.14(C)(1) prohibits making terminations at those ampacities unless the equipment is "listed and marked otherwise". If the equipment is not "listed and marked otherwise", you will have to use the ampacities of 310.16.

IMO, this is overboard, but it is what it is.
 
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hardworkingstiff

Senior Member
Location
Wilmington, NC
and....

and....

In case you weren't aware, the terminations points on the breakers and neutral/ground bars are not rated to accept W cable. You will have to use a pin terminal or convert to a standard building wire. This would probably hold true for any mechanical splicing kits you try to use with the W cable.
 
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nhfire77

Senior Member
Location
NH
hardworkingstiff said:
In case you weren't aware, the terminations points on the breakers and neutral/ground bars are not rated to accept W cable. You will have to use a pin terminal or convert to a standard building wire. This would probably hold true for any mechanical splicing kits you try to use with the W cable.
Click to expand...

Is this because of the stranding/roping of the conductor?
(I have never tried to land W cable in a panel before.)
 
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220wire

Member
I wasn't aware about the terminals being rated for type-w. I used butt splices in the past but had to step up a size. I did everything I could to cram the wires in with out trimming.
As far as ampacity goes, the manufacturers seem to have a higher raing then 310.16. I am guessing because the conductors are compact.
I have managed to land them in a panel before. I think it was a cutler hammer panel.
 
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hardworkingstiff

Senior Member
Location
Wilmington, NC
220wire said:
I wasn't aware about the terminals being rated for type-w. I used butt splices in the past but had to step up a size.
Click to expand...
I'm curious, what compression tool did you use and what setting or dies? Did you use the die size of the cable or the die size of the up a size butt splice?
As far as ampacity goes, the manufacturers seem to have a higher raing then 310.16.
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That's my point exactly, the cable is rated higher ampacity, but you are not allowed to terminate it at that ampacity unless you have special markings on the equipment terminations saying it's rated for the higher ampacities.
I have managed to land them in a panel before. I think it was a cutler hammer panel.
Click to expand...
I've done it before myself. I just know (from inspectors and manufacturers reps) that the standard equipment we use is not rated to accept the fine strand cable.
 
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nhfire77

Senior Member
Location
NH
hardworkingstiff said:
I believe it is.
Click to expand...

Makes sense. I have very limited history with W cable, I was on a few industrial jobs where we used the "locomotive" cable, it was in a shipyard, but not on a train. I believe that was similar in construction and was a bear to deal with. There was some engineer approved transition prior to any panel.
 
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220wire

Member
I had 4/0 type w with 250mcm butts crimped with an old crimper my uncle gave me and sized it for 250's. The wire fit nicely in them

I'd rather do it right and knowing what you have explained I feel better prepared. Thanks.

I am still worried about the ground rods on the dock. It doesn't sound right for some reason. I'm just a bit perplexed
 
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