The High Limit Reset Switch is a safety device that shuts off ALL POWER when the water gets too hot, like around 170F. It is to prevent a runaway tank in which the thermostat has failed and is continuously heating the water.
That case would result in the water getting to boiling and maybe even blowing up the tank.
Sometimes under solar operation the water can also get super hot, especially if the house has been vacant for weeks.
So before you call for a pricey troublecall, try to see if this switch had been activated by trying the RESET
You open the door as shown in image 1. You should turn off the breaker because there is live 240V inside here. The breaker will always be a 2-Pole 30 Amp breaker (a double breaker).
Then as in image 2, press the Reddish / Burgandy button and pay close attention to any click.
The click will be faint, but it will be there if it was activated into safety shutoff mode. If you got the click, you probably solved the problem.
Turn breakers back on, flip the Little Gray Box (Timer Box) to the right which is the on position.
In 20 or 30 minutes you should have hot water. If not, there is still a remaining problem.
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