I did a few things wrong here, but posting about it in case anyone else has one of these -
#1 wrong thing - didn't have a GFCI on the outlet it was plugged in to (I've found there are portable ones you can use to convert an ordinary outlet into a GFCI one!)
#2 wrong thing - I thought the small cracks in the insulation on the wire couldn't cause a problem - one of those small cracks ended up allowing the wire to contact the tank, melted it down until it contacted the fence, where it caught fire
#3 wrong thing - I didn't have the metal "cage" around the floating heating element - they sell that separately. I had one but I guess it broke & I didn't see why I needed it - it might not have helped prevent this but would if the water got low, etc.
The good news I was home & noticed it just as the flames started licking the fence & dry brush below it.
The hilarious thing is, after I unplugged the heater & ran to the tank to put it out, I was shovelling dirt on the flames because the hose was frozen - seemed to take forever before I realized the tank was full of water I could use to splash on the flames Put it out pretty quick after I came to that realization
I was very lucky, but thought I'd post the things I did wrong in case anyone else has one of these heaters.
I'm going back to the plug in ones! I bought that and a portable GFI & new tank.
All's well that ends well but sheesh! That could have gone bad - fence connects to my house & barn & close to neighbors - all flames had to do was follow the fence line
while you have the electrician there, have them check you main panel to see why the circuits breaker didn't trip when the circuit went to dead short... you may have a common usage of grounding rod (L2 is normally the return leg --white wire for 120 volt circuits)
Or worse …you main panel maybe one of the recalled panels that was sold through the big box stores…there were tens of thousands that are defective.