On a duel element residential water heater, both elements do not heat at the same time. Starting with a tank of cold water, the upper thermostat will energize the upper element.

Should both water heater elements be on at the same time?

Only one element will come on at any one time. This is known as a flip/flop system. On a 240 volt water heater, there will always be 120 volts to both elements. … When the tank is full of cold water, the upper thermostat will take priority and heat up the top portion of the water to the setting of the thermostat.

How does a two element hot water heater work?

A dual-element water heater uses two heating elements controlled by two separate thermostats. The upper element heats the upper portion of the water column. When it reaches a specified temperature, Rheem notes that it shuts off, and the lower heating element takes over, heating the rest of the water.