• How do I protect my AC from lightning strikes?

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  • Twice in the last three years my AC compressor has been struck by lightning.  I live on a hill and lightning strikes seem to be a problem.  Along with my AC (a circuit board inside the AC compressor metal box) my sprinkler system has been struck and traveled up the control lines to the control box in my garage.  There have been at least 5 lightning strikes on sprinkler systems on my hill over several years.  Twice on me and three others that I know of.  I have protected the control box with fuses on the control lines going into the control box.  The AT&T lines are also affected and I have put a surge protector on the phone line.  I have a whole house surge protector to prevent lightning from coming in through the power lines.  The last thing I need protected is the circuit boards in the compressor where the lightning enters and blows the circuit board in the compressor as well as a circuit board inside the house.  I only have about 6 inches of dirt in my yard then it is solid limestone after that.  I have searched online and had very little success with only suggestions of grounding the compressor (not easy to do with the ground I have) and building a Faraday cage around the compressor.  Lightning rods would also be difficult due to the solid rock this neighborhood is built on.  I have suggested that a "neighborhood lightning rod" might be a good thing to the HOA president and got nothing but a quizzical  expression.  I want to stop the next strike from causing damage to my AC which is the most expensive items to fix in the last two strikes

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    Question by richsnook1
    09/15/2017

It sounds as if the only thing you haven’t actually tried is a lightning rod system, which also sounds as if it’s the best solution.

My thought is that your efforts to isolate your compressor aren’t working well enough so that a rod system would at least give the lightning a different target and would relieve your arrestors a bit.

Have your tried insulating your compressor? Maybe a non-conductive pad and a dielectric section of tubing? And add a rod specific to your compressor?

I realize rock is a problem. I’m in the telecom business and remote sites have to be grounded despite soil problems. Not my direct responsibility but solutions have included some sort of salt solution (in the holes with rods) that increases the conductivity of the rods. Also, rather than rods, a halo of bare copper ”strap” really increases the exposure of a grounding material to the ground (the ”halo” generally is buried around the perimeter of a building). Both of these solutions are used on hilltop sites with success.

Answer by Wayne Ruffner
10/17/2017
Answer by mattbrown
12/12/2017
Answer by leesmith
12/14/2017
Answer by leesmith
12/14/2017
Answer by leesmith
12/14/2017
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