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Considering building a stand alone lightning rod

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  • Considering building a stand alone lightning rod

    First of all thanks for all the great info on this site! I have just a small 1.2 kw micro inverter set up on my 2nd story roof. Recently we had a serious thunder storm with a couple of big thunder claps close by as I lay awake at 4am...made me think about how much I don't want a direct strike and what else I can do for protection. Read up on lightning rods but really don't want to attract a strike either, however I already have a lot of metal on top of the tallest roof on the block. It occurred to me I could build a stand alone lightning rod a few feet from the house with its own seperate ground rod not connected to my electrical system. Theoretically protecting 25' radius that would cover the second floor. I assume it would be better to keep it off my ground system. This lightning rod would be 50' away from my main panel and my service is underground. Additionally I'm going be inspecting my grounding system, make sure gas and water are bonded. I know my sub pole has a butt wrap coil of #6 at the base as well 2 grounding plates (90' from house), pool has a ground loop (30' from house), I might not have any grounding closer except utility piping. Seems It would be better to have a rod closer like at the outdoor sub panel that feeds the house. Any advice would be very much appreciated!

  • #2
    Flagpole ? With lots of ground radials & mesh
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

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    • #3
      The problem with a lighting protection system over a structure. While it may keep the lightning from directly striking your home, it will not guarantee the electrical surge from finding a path from the ground back up into the electrical system of the house.

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      • #4
        Mike, yes pretty much a flag pole or ariel antenna mast with good grounding.
        SunEagle, wouldn't the surge from the ground up be the lesser of 2 evils? I figure if it strikes the rod it would have hit the adjacent panels not given the option. Or is it not worth my trouble? Maybe spend more time and energy with better grounds and surge protection? I have a Ditek panel Surge Suppressor DTK-120/240CM for 72KA protection, which isn't much. Not really in the lightning belt here but its been a wet and stormy 2 years, with 3" of rain in the current 7 day forecast.

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        • #5
          Originally posted by gtojohn1965 View Post
          Mike, yes pretty much a flag pole or ariel antenna mast with good grounding.
          SunEagle, wouldn't the surge from the ground up be the lesser of 2 evils? I figure if it strikes the rod it would have hit the adjacent panels not given the option. Or is it not worth my trouble? Maybe spend more time and energy with better grounds and surge protection? I have a Ditek panel Surge Suppressor DTK-120/240CM for 72KA protection, which isn't much. Not really in the lightning belt here but its been a wet and stormy 2 years, with 3" of rain in the current 7 day forecast.
          If you had a choice, then the ground surge would be the lesser of the 2 evils but I may ask is the loss of your solar panels worse then the loss of your any critical electrical appliances throughout the home?

          When I use to work for a company that had a plant in the Middle of Florida, I helped them find a way to mitigate electrical surges that hit the ground on their property and entered the building through the utilities wiring/piping. We installed optical isolators on the phone system since that is what took the hit most of the time after a storm. There were other surge mitigating equipment installed but we found there really wasn't a fool proof way to keep the "lightning" out of the building. It comes down to protecting the most important equipment and wish for the best.

          It is a two edge sword when you install a lightning protection system. On one side it should protect the structure from a direct hit but on the other side it may attract the lightning to the building. Then you better have a quality "grounding system" installed to direct the energy surge away from the critical electrical components.

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          • #6
            Guys thanks for the fast responses. Hmm...since my panels are already bonded to my electrical panel a strike would probably surge all my grounds anyway, right? or am I missing something? Sounds like it is better to have lightning rod ground separate from house grounding. Looking out the window there are utility poles and wires all around so the house isn't the lone tall point in the middle of a prairie. I'm thinking Lightning rod just 24" above roof ridge for 25' protection but low enough to not attract unwanted strike.

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            • #7
              Originally posted by gtojohn1965 View Post
              It occurred to me I could build a stand alone lightning rod a few feet from the house with its own seperate ground rod not connected to my electrical system.
              I do not know where you came up with that idea, but forget it. Not only does not comply with any electrical codes, but extremely dangerous, and asking to have all your equipment destroyed.

              Originally posted by gtojohn1965 View Post
              Theoretically protecting 25' radius that would cover the second floor. I assume it would be better to keep it off my ground system.
              Same answer as before if I understand you correctly



              Originally posted by gtojohn1965 View Post
              This lightning rod would be 50' away from my main panel and my service is underground. Additionally I'm going be inspecting my grounding system, make sure gas and water are bonded. I know my sub pole has a butt wrap coil of #6 at the base as well 2 grounding plates (90' from house), pool has a ground loop (30' from house), I might not have any grounding closer except utility piping. Seems It would be better to have a rod closer like at the outdoor sub panel that feeds the house. Any advice would be very much appreciated!
              Here is what you need to know. Every Ground Electrode must be bonded together to form a common Ground Electrode System. That means every rod, pipe, plate, radial etc... In other words all bonded together to make a singular system.
              Last edited by Sunking; 01-09-2017, 11:05 PM.
              MSEE, PE

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              • #8
                " extremely dangerous, and asking to have all your equipment destroyed."
                Sunking, could you elaborate a little more why so I can understand? You obviously know your stuff, and that's why I found this forum,but wouldn't avoidance of a direct strike to my panels cause less damage to my equipment and home than a strike grounded to earth 50' from my service panel?
                Thank you for your time.

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                • #9
                  Are you trying to build a decoy using Cone of Protection? If so you are better off and money well spent making sure you Ground Electrode System is up to code and you panels are properly bonded and down conductors routed correctly before you do that. Have your utility install a SPD collar on your meter.
                  MSEE, PE

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                  • #10
                    I agree with Sunking. If I had a potential lightning problem I would invest in the ground electrode system and make sure the wires were properly bonded and as big as possible to help direct the energy away from the equipment and into the ground.

                    The "cone of protection" needs to be over the home for it to provide some protection. Having a decoy for the lightning to strike away from the home is not a guaranteed mitigation plan.

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                    • #11
                      Yes, your Decoy flagpole needs to be engineered, not just stuck in like a javelin. It will need multiple ground points to dissipate a direct strike and you dont want gradient voltages in the ground system to use your house as part of it's ground .
                      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                      solar: http://tinyurl.com/LMR-Solar
                      gen: http://tinyurl.com/LMR-Lister

                      Comment


                      • #12
                        Yes, decoy was what I was going for. I will start with the ground and bonding of my house first. I bought 3 ground rods and more bonding clamps for water and gas last weekend. Once I get those I might get a few more to cover the perimeter of the house, pier and beam easy to run wires. I have a few extra spaces in my panel would there be any point in adding another or different panel surge protector? I know the spd at meter can is better but, call me crazy, I really don't like renting equipment paying fees or inviting city utility people on my property.

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                        • #13
                          There is no better place for a SPD than your meter can. Any other place is just a waste of money. TVSS starts at the Service Entrance and is the Brute Force Guard so to speak. It is the largest unit. Then you use point of use devices like say your entertainment cents or office equipment like a puter, printer blah blah.

                          The most common mistake electricians make is using SPD that require wire. That pretty much defeats their purpose. The kind that mounts next to the Main Breaker Panel. Meter Can Collars have no wire. You pull the Meter out, plug the SPD, then plug the Meter back into the Collar.

                          Lastly when solar is involved is how the panels themselves are bonded. John Wiles the Father of Solar who wrote the NEC 2014 cycle Article 690 in an attempt to keep cost down really screwed up by allowing Solar an exception to use an Equipment Grounding Conductor ran with line conductors. Most Jurisdictions amended that part out because of the extreme danger that is created inviting Lightning right into your home and has to pass right through your inverter to find dirt back at the Service entrance via the Main Bonding Jumper. Panels should be treated like Air Terminals (aka Lightning Rods).
                          Last edited by Sunking; 01-11-2017, 10:58 AM.
                          MSEE, PE

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