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Surge Protection, Grounding, Lightning, extension cords
(06-11-2019, 10:19 PM)Roadtripp Wrote: it sounds like the surge came from the new building and extension cord backfeeding the panel and inverter AC side.

In a regular house there is a ground rod at the service entrance and neutral is tied to the ground rod there.  In the main panel all the safety grounds are tied to the neutral in that one place.  

With an inverter or portable generator set up there may be no main panel, there might be no ground rod anywhere.  Safety grounds might be all tied together, maybe not.  There might be no neutral connection to ground.  If it is an RV it might be plugged into an RV 30 amp pedestal that might have safety ground connected correctly to neutral in the main panel.  That safety ground might be connected to the vehicle, or not.  

What probably killed this inverter is a common mode high voltage from the extension cord antenna.  Common mode means both the hot and the neutral went to 10,000 volts together but still only 120 from neutral to hot.  Without a neutral to ground connection the voltage rises until there is a spark.  With the extension cord antenna many volts built up with nowhere to go until the voltage got high enough to cause a spark.  A wire connecting the inverter output neutral to inverter dc input minus would prevent a large voltage build up across the inverter by dissipating it slowly over time.  

The spark always happens inside the most expensive piece of equipment.  Electricity takes the path of least resistance.  Silver is an excellent conductor.  Thirty pieces of silver have very low resistance.  Logic.

Surge protectors respond to differential high voltage not common mode.  If the 120 from neutral to hot gets too high like 240 the surge protector MOV (metal oxide varistor) will conduct.  The inverter itself connected the neutral to hot driving it to 120.  There was nothing to drive it too high.  Lightning did not hit just the hot wire in the extension cord.  Differential high voltages are usually caused by bad wiring that connects 240 to a 120 RV input.  That has nothing to do with an extension cord antenna in a storm.  Typically MOVs don't have enough current capacity to trip a 20 or 30 amp breaker so they just go open circuit.
Say good night, Dick.
[-] The following 1 user says Thank You to Trebor English for this post:
  • rvpopeye (06-13-2019)
OOOOO as Kaylee would say Tron Porn !
Juicy "under the hood" details too !
It's rare finding the good stuff anymore................

If anybody had trouble making it through that , it all checks out !
Give Trebor the password to your breaker panel.
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