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Since my utility pole is halfway between my house and pole building (shop), there is a meter at each service entry. My (house and shop) panels are grounded properly with ground rods and subpanels are also properly grounded (with neutrals NOT bonded/attached to the ground bar). I've just read here about the possibility of a problem if metal pipe or shielded cabling were to connect between the two structures. What precautions should I take, if any?

  • What cabling or piping is ran between the two buildings? Or, what piping or cabling do you plan on running between them in the future? – Mister Tea Nov 29 '16 at 15:18
  • No connections between the two presently, other than electric from transformer. Possibly water, gas, Ethernet and /or cable for TV – dale_z28 Nov 29 '16 at 15:23
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If you don't have any piping or cabling between them, don't worry.

If you are planning to run coax, use a ground isolator designed for your type of CATV or satellite system. Your cable co might even be able to provide one which is guaranteed to work with your service.

Ethernet is already ground isolated thanks to transformer coupling so it's not ground referenced. It's part of the spec and was there from the start to specifically address concerns like yours. There is shielded Ethernet cable which is uncommon but should be avoided and most likely unnecessary.

Piping will be tricky. You are going to need what is called a dielectric union or other galvanic isolation device. Then bond the pipe on both sides of the union for lightning and grounding safety. The bond should not jump the union but rater establish ground at their respective building locations. This applies if your piping is metal. So if permitted by local code, run plastic pipe and problem avoided. Gas piping can also be plastic if permitted.

And lastly, use lightning arrestors on both sides of your ethernet and coax wiring at each building end. Bond them strait to a solid ground or their own properly installed ground rod.

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