double check my dock power design?


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Old 06-17-19, 11:36 AM
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double check my dock power design?

I am running 6 AWG red/blk/wht THHN's with 10 AWG insulated grn/ground wire thru 1" pvc conduit 24 to 18" cover 90 feet to a seawall subpanel, fed from an ordinary 2P 60A breaker inside the house.

At the subpanel, i will have a 30mA leakage current protected breaker feeding a 30A 120V marine twist lock outlet. In addition, a GFCI 20A breaker feeding a 120V receptacle, and a 240V 15A 2P ordinary breaker to feed a lift motor system with no receptacles.
Does this design comply with the latest NEC ?
 
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Old 06-17-19, 12:39 PM
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I don't see any issues that stand out. Use lots of PVC for better wear near the sea.
 
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Old 06-17-19, 01:08 PM
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Looks OK to me................
 
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Old 06-17-19, 01:40 PM
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thanks guys; I'll let you know how the new Leviton panel works out too.
 
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Old 06-17-19, 09:39 PM
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Online I found this excerpt from the 2014 NEC Handbook:

210.8 (C) Boat Hoists. GFCI protection shall be provided for outlets
not exceeding 240 volts that supply boat hoists installed in dwelling
unit locations.


The proximity of this type of equipment to water and the wet or
damp environment that is typical where boat hoists are used is
the reason for this GFCI requirement. Documented cases of electrocutions
associated with the use of boat hoists compiled by the
U.S. Consumer Product Safety Commission substantiated the need
for this requirement. The GFCI requirement applies only to dwelling
unit locations and to boat hoists supplied by 15- or 20-A
branch circuits rated 240 V or less. It is important to note that it
applies to all outlets, not just to receptacle outlets.
Therefore, both
cord-and-plug-connected and hard-wired boat hoists are required
to be GFCI protected.


Also, the 2017 NEC requires ground fault protection on any breaker supplying a feeder conductor to the dock. The 2017 NEC originally stated that this breaker had to trip at or below 30mA. There have been amendments since to allow higher than 30mA. If your area is still on the 2014 NEC then the feeder does not need ground fault protection.
 
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Old 06-18-19, 04:07 AM
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Hi, donít believe you can use THHN under ground, should be THWN for wet or damp locations.
Geo
 
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Old 07-12-19, 07:30 AM
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OK; thanks for all the remarks; Although the mission has gotten a bit more complicated. Instead of a simple dock with a lift, it is now a Boathouse with a lift.
As I read the NEC, now a ground rod is required and a disconnect just before the "dock". I take that to mean a single switch much be within a short distance on LAND that will kill all dock power. There is some confusing verbage regarding this "terminal box" and "disconnect". I will take it that the subpanel may exist in the boathouse, rated for DAMP, only if under cover, but that the several breakers within won't qualify as a disconnect. True? Note the context is NOT a public marina, but a single residence boathouse. All the construction will be based on 6 or 8 wood piles, over salt water. Also, I read about 6AWG bonding all touchable metal items, including ladders, structural metal, and any other large metal work, connected to the subpanel. Plus, no outlets within 6' of the water ladder.

There is verbiage about "single feeder". I take that to mean ONE conduit, with one disconnect going to the subpanel. Also, I will drive the FEEDER from the house load panel with a 2P 60A with 30mA protection. This will offer protection of the 30A/120 twist lock; In addition to the GFCI local protection of both the 240V lift (via 2x 2P GFCI breakers) and the 120 convenience recept.
 
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Old 07-12-19, 03:18 PM
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You need a GFCI for personnel protection which has a 4-6mA trip. A 30mA GFCI is only for equipment protection and only a few things need that, which a boathouse/boat hoist are not one of them.
 
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Old 07-12-19, 05:09 PM
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The panel must be 3 foot or more above flood level IIRC.
 
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Old 07-14-19, 03:21 PM
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My only remaining question has to do with disconnects.

Is a dock-local disconnect required to kill the 60A feeder? Obviously, there is a breaker at the main panel at the house for the feeder.

A cleaner install to have just a subpanel in the boathouse, with the bonding and GEC wires running to it. If a shore mounted disconnect was used, then the GEC would wire into that instead.

I'm sure my AHJ will have input; I just want to submit an initial plan that is pretty close.

Storm Matthew push water up 6' above normal high tide. All my panels will be as high as allowed (79" to top breaker).
 
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Old 07-14-19, 06:38 PM
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Is a dock-local disconnect required to kill the 60A feeder?
No. The breaker in the house panel is all that is needed. You will need a disconnect at the boathouse panel. This can be up to six disconnects or a single switch/breaker.

A cleaner install to have just a subpanel in the boathouse, with the bonding and GEC wires running to it. If a shore mounted disconnect was used, then the GEC would wire into that instead.
Not sure what you mean. You bond the Equipment Grounding Conductor
(EGC) to the panel.
 
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Old 07-15-19, 05:17 AM
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Not sure what you mean. You bond the Equipment Grounding Conductor
(EGC) to the panel.
No, my worry is where to run the #6 going to the ground rod. Subpanel or this other single handled disconnect I was thinking of. But, if no local single handle disconnect is required, that makes that an easy decision.
 
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Old 07-15-19, 06:25 PM
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You only need a single breaker that will act as a disconnect, or you can have up to 6 breakers using the six-throw rule.

The #6 going to the ground rod is connected to the ground bus. The neutral bus will remain isolated from the ground wires.
 
 

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