Unintended ground rod

[robbob2112]

The lighting protection system will have its own ground rods. Usually at each corner of the building and possibly more spaced between, if the distance is great.
Then a single connection from the electrical system ground rod to the nearest lighting protection system ground rod.

Just to get straight in my head -

Assume a shed with metal roof 100ft from house with solar panels on it. Shed structure is wood - I would run a EGC from the hose and connect the roof and panel frames to it so everything is the same potential.

Same shed, but with metal frame sunk into the ground - I assume I would have to do the same to keep things at the same potential even though the frame would act as ground there.

Now - we already talked about this one - metal mast with weather station on it, but no electrical connection to the house - ground rod next to it, no wire to main rod. If anything with electrical connection to the house grid gets added, an EGC gets added at that time to tie it all together.

Correct?

My understanding since joining the board and learning a few things is keep everything at the same potential and extra ground rods are bad, but if they exist must be tied to the main ground rod.

 

[seneysolar]

I think its worth mentioning that the reason to eliminate "ground loops" that may have a different potential, is not for lightning protection purposes.
It is simply to maintain circuit-level protection in a ground fault scenario.

Building a solar array that could withstand a lightning strike would be an interesting but separate topic.

 

[timselectric]

Assume a shed with metal roof 100ft from house with solar panels on it. Shed structure is wood - I would run a EGC from the hose and connect the roof and panel frames to it so everything is the same potential.

Yes

Same shed, but with metal frame sunk into the ground - I assume I would have to do the same to keep things at the same potential even though the frame would act as ground there.

Correct

Now - we already talked about this one - metal mast with weather station on it, but no electrical connection to the house - ground rod next to it, no wire to main rod. If anything with electrical connection to the house grid gets added, an EGC gets added at that time to tie it all together.

Correct?

Correct

My understanding since joining the board and learning a few things is keep everything at the same potential and extra ground rods are bad, but if they exist must be tied to the main ground rod.

The existing grounding system. Not necessarily the ground rod.
The purpose is to provide a fault current path to the N/G bond.

 

[timselectric]

I think its worth mentioning that the reason to eliminate "ground loops" that may have a different potential, is not for lightning protection purposes.
It is simply to maintain circuit-level protection in a ground fault scenario.

Building a solar array that could withstand a lightning strike would be an interesting but separate topic.

Exactly
Lightning protection is a completely different system.
Usually too cost prohibitive for anyone in this forum.

 

[ULR]

What about anyone with a propane tank and ___ feet of copper line buried in the ground? Or a point well with ___ feet of steel pipe in the ground? Both of these are likely to lead to appliances that are grounded, and ultimately grounded to the main panel.

Propane tanks are normally installed with plastic pipe underground and the transition to metal pipe most of the way up the vertical run where it exits the ground. It will have a metal wire run along it but with the end hairpinned just before the end of the wire, with the loop several inches below the transition. The pipe is plastic mainly because metal pipe corrodes much faster underground, leading to hard to find gas leaks. The wire is to hook up a low-power electrical signal generator for locating and avoiding the plastic pipe during excavation. But this arrangement also avoids trouble with underground currents from nearby lightning strikes and surge currents from capacitive coupling to cloud discharges.

It is my understanding multiple grounds are not bad as long as they all have the same potential. You don't want 2 points in a circuit to have a different ground reference. I assume this is why NEC wants your PV system ground ran all the way back to the main panel ground. If they all run back to the same point, they all have same potential.

Tying the electrical system ground to the rest of the grounding system at only one point arrangement avoids lightning currents between ground rods leaving the ground rod system and traveling in the electrical system conductors (which aren't up to it).

It's similar to how tying the protective ground (green/bare) to the neutral at only one point avoids neutral power currents traveling along the green/bare system, so the latter only needs to be big enough to handle fault currents and segments can be sized according to the load on the circuits they are serving.

 

[seneysolar]

Propane tanks are normally installed with plastic pipe underground and the transition to metal pipe most of the way up the vertical run where it exits the ground. It will have a metal wire run along it but with the end hairpinned just before the end of the wire, with the loop several inches below the transition. The pipe is plastic mainly because metal pipe corrodes much faster underground, leading to hard to find gas leaks. The wire is to hook up a low-power electrical signal generator for locating and avoiding the plastic pipe during excavation. But this arrangement also avoids trouble with underground currents from nearby lightning strikes and surge currents from capacitive coupling to cloud discharges.

I assume it's different state to state. I was just using it as an example of the OP's concern for creating another ground rod. Here in Michigan most are buried bare copper line. Only recently have they started using plastic coated copper line. I have not seen any come out of the tank and transition to plastic (no copper) for the underground portion and then transition back to copper at the house.

They do run buried PVC gas line (with tracer) for natural gas service from the street/utility.

 

[SoggyShoes]

This is dangerous. They must be bonded to the electrical grounding system, to make them safe to touch.
Usually this is done at a single point, at ground level. Preferably below grade.

Maybe they did bond it underground. I know there was no connection in the house. I just remember it was a really expensive add-on that I didn't think we needed in Oregon.
Unfortunately the framer talked to the clients and freaked them out.
There was a lot of very expensive cable going from a very expensive custom welded spire at the peak of the roof straight to ground rods.