Question about monitoring panel wiring after a lightning hit in Ohio

We had a job outside Columbus last Thursday where a direct strike fried the panel but somehow left all the sensors intact. I always assumed the surge would take everything out together, but the keypad and main board were toast while every door contact still read fine. Has anyone else seen a partial failure like that, or did we just get lucky with the way the ground loop was set up?

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wright.finley29d ago

Doubt it was luck at all, more like the strike found the easiest path to ground and that path ran through your main board and keypad instead of the sensor loops. Think about how the wiring is laid out, the keypad and panel sit right at the point where the surge comes in, so they eat the hit first and the sensors downstream never see the full current. Door contacts are also way more forgiving, they are just simple mechanical switches with no electronics to cook, so even if some voltage got to them there is nothing in there to fry. A direct strike does not spread out evenly like people assume, it dumps current wherever the resistance is lowest and that is almost always the panel. So your sensors reading fine does not mean the surge missed them, it means they were built to survive what little made it that far. I would still meg them out and check for welded contacts before you call that job done though, because a contact that reads closed on a meter can still be stuck and give you callbacks later.

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