I have a home that has been a victim of lightning strikes to electrical sources with in our home. The most recent chain of events is my furnace & Electric hot water heater both malfunctioning on the same day a day after a group of storms came thru the area. Our house was built with I. Very close proximity to underground ledge. Is it possible the grounding rod is not doing proper grounding because of the closeness to the ledge where the ledge may be absorbing the hit & transferring to the electrical grid of the house.

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    What is an "underground ledge"? – isherwood Jul 5 '18 at 14:36
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    I completely agree with adding a whole house surge suppressor (so + to Ed Beal), and have tried to convince people to install them for many years, but it would probably be a good idea to have someone survey your ground system and make corrections if needed. We really couldn't give you a definitive answer unless we were onsite with a megger (electrical meter that measures ground resistance). – Retired Master Electrician Jul 5 '18 at 15:36

Even with a good solid ground a strike on the grid can damage equipment to the point of blowing the breaker panel to pieces with a hit that is close to the house. For indirect hits a whole house surge suppressor (the largest you can afford) may reduce or eliminate damage to home equipment. I state to use the largest you can afford as when these devices take a hit over their ratings they are damaged, sometimes wiping out the varistors in the device so it has to be repaired or replaced (larger units usually have replacement modules for each leg or phase depending on the service type).

  • I had to look up MOV, so I changed it to "varistor" for clarity. Feel free to re-edit if that's wrong. – isherwood Jul 5 '18 at 14:39
  • There are different type of varistors , metal oxide varistors have a break down voltage and conduct other types control more like a switch for example. – Ed Beal Jul 5 '18 at 14:43
  • Fair enough, but is that distinction critical to our understanding of your answer as laypeople? – isherwood Jul 5 '18 at 14:45
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    If MOV is not understandable defining it in parentheses might be better. i.e. “MOV (Metal Oxide Varistor)”. As I was reading the answer I thought varistor makes this unclear, why did he choose that word? When I got to the comments I found out... – Tyson Jul 5 '18 at 15:54

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