I do this all the time with my setup except I do have a heavy duty contractor type extension cord. Its a 10GAUGE type. No issues here with my 13,500btu air conditioner... Those red-oragne extension cords from WALMART are not heavy duty enough to use for this application. Think those are only 14guage cords...
I also have one of these RV plug in 120VAC meter that has the safe use scale on it... Pretty handy to have in plain view somewhere making sure my 120VAC is a good safe level to use...
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Also make sure all three conductors are being used with the extension cords. This is the only Earth Ground for your trailer coming from your house reception. I always check with one of those Circuit Testers to be sure the 120VAC receptacle I am using on the house side has the ground connection working... Got mine from LOWES...
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Roy Ken
