I live in NE Alabama and am building a boathouse. Part of the dock is built on 6" I-beams driven into the lake bed and has wood decking on top, the boathouse is being built on wooden pilings and it is attached to the dock with I-beams. I plan to install a 60 amp GFIC at the service box for the home, then run 3, #4 THWN wires and a #8 ground in pvc approx 160' to a sub panel located on the boathouse and use regular breakers there (I will have 6 or less breakers). I will keep the ground and neutral separate at the sub panel. After pouring over the NEC and reading about every article I can find, I still have a few questions.
I understand the height location requirements of the sub-panel, but can a weather-proof sub panel be located on one of the supports for the roof (on the fixed dock itself? (there will not be a wall, just a roof). Most of the info I can find about Equipotential Plane is for outdoor pools or spas. Do I just bond the I-beams together then drive a ground rod (3/4" water pipe no less that 8' long) into the lake bed, next to an I-beam and run a #8 copper ground from the bonded I-beams and ground rod to the sub panel ground?
The NEC talks about having the Equipotential Plane extend 36" around the disconnect, which I believe in my case, would be the sub-panel? Does that mean that there should be an Equipotential Plane (wire grid) on or beneath the wooden deck directly under the sub-panel? Thanks for your expertise greg

  • What make and model is said 60A GFCI? – ThreePhaseEel Sep 27 '18 at 3:59
  • It is a GE 60 amp Spa Panel – 1_greg_1 Sep 27 '18 at 20:53

Have you checked 553.1 , 553.8 grounding. 553.8.D Requires a ground rod , I put 1 at the shore power disconnect, 555.1 ? This is the article you are looking for. 555.2 the datum plane for mounting equipment . It sounds like you are looking at swimming pools . Hope this helps

  • Thank you for the response. I did look at 553 but thought it was for floating buildings. My dock/boathouse is fixed, part metal, part wood. I was looking at 682 and wanting to put the sub panel under the roof of the boathouse. My thought was to drive two ground rods in the lake bed itself and bond those to the I-beams (dock supports) then connect to the ground in the sub panel. I just didn't know if driving the ground rod in the lake was approved or not. (the water level is lowered each year allowing access to the lake bed). – 1_greg_1 Sep 27 '18 at 20:51
  • How deep are the beams driven? If 10' they should be sufficient. The buildings over the water here require the service disconnect to be on land. – Ed Beal Sep 27 '18 at 21:29
  • I am fairly positive they are not 10'. Guess I need to check to see if a panel is allowed on the dock. If so, whether a disconnect is required on the shore side. – 1_greg_1 Sep 27 '18 at 22:13

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