When packing up as we leave a site I put a small piece of black insulation tape on the switch so it doesn’t get switched on accidentally, I had several occasions where there was no hot water because I’d connected the EHU and when I’d fill the water system there would be no hot water until I’d pressed the reset button or on one van I had to turn the heater off for a few minutes to reset itself, I luckily got away with no damage to the water heater, hence the black tape over the switch.
BP