Outlets circuit died using H2O heater... why??

[AKBambi]

I recently purchased a 1961 Bambi with original wiring and utilities. I fired up water heater for the first time - after about 25 minutes, I smelled a slight burning odor (like plastic or solder) but couldn't find anything wrong. Water heater was working great. I had nothing plugged into the wall sockets... I don't even think I had a light on. In any case, the 110 wall outlets stopped providing power, and the breaker was tripped. I reset the breaker, but the outlets don't work. I thought the only power used by the water heater was for the piezo switch... that seems like a minimal draw. If neither of the outlets work, then I assume I must have fried a line between the first outlet and the breaker box... so, can anyone think of how I would have done that by ONLY using the water heater?? Maybe a wire was threaded too close to the burner chamber and it melted? I don't really have great access to the rear of the tank to explore... I BTW - I picked up the Bambi in Vermont and drove it to Alaska over a 10 day period, throughout which the outlets worked just fine. It wasn't until I fired up the water heater that I smelled the smell and lost power to the outlets. Any thoughts?

[AKBambi]

Another thought I had was maybe there is a cathode or some other sensor in the heat tank that draws power? Can anyone tell me about the water heaters that went in the 1961 Bambis? What prevents over-heating the water and/or over-pressurizing the system? Anything else drawing power that I am not thinking of?