You should have lots more views and subscribers. Nice and useful videos, explanations, with animation, pictures and real videos of everything talked about. I just found out your channel earlier today and i had to give you credit for all your good work.

"One element can operate at a time" is what we as electricians and plumbers refer to as "non-simultaneous operation ". Probably 99 percent of residential water heaters are in this configuration. "Simultaneous operation " means both elements can operate at the same time, and this requires two 30 amp 240V circuits, or one 50 or 60 amp circuit depending on whether the elements are 4500 or 5500 watts, and both thermostats must have a high temperature cut-off since they operate independently. You'll most often see this in a commercial application such as a restaurant, or in very rare instances, a home with a very large family and extremely high hot water demands where non simultaneous operation cannot meet the demand and a larger tank or two units cannot be installed for some reason.