Do electric water heater elements turn on simultaneously?

[Stephen Tashiro]

Can the two elements in a typical electric water heater turn on simultaneously?

The web page http://waterheatertimer.org/How-water-heater-thermostat-works.html says:



The operation for typical residential non-simultaneous 2-element tanks is more complex since the heater has two thermostats, the upper thermostat and lower thermostat. The thermostats are wired so that only one element is ON at any one time.
The upper thermostat heats top 1/3 of tank to set point, and then switches electricity to lower thermostat that finishes heating whole tank.


It isn't clear to me whether the phrase "typical residential non-simultaneous" implies that "non-simultaneous" is what is typical. (It could also mean that there are two typical types of water heaters - typical simultaneous and typical non-simultaneous.)

[Kev Williams]

I would wager that non-simultaneous would be 'typical'. From what I read 220v water heaters use 4500w elements. To run 2 at the same would require separate 40 or 50 amp breakers...

[Bruce King]

When the top element sees the right temperature it switches to the bottom so one at a time.
Poor hot water means typically a bad lower element.

[Jim Koepke]

When the top element sees the right temperature it switches to the bottom so one at a time.
Poor hot water means typically a bad lower element.

+1 On this. This was a problem with our electric water heater. The water would start out nice and hot, then after very short use the water would be cold. The lower element was getting current but an ohm meter indicated it was open. Replacing the lower element fixed the problem. Don't forget to turn off the water and drain the tank first.

jtk

[John K Jordan]

Can the two elements in a typical electric water heater turn on simultaneously?

The web page http://waterheatertimer.org/How-water-heater-thermostat-works.html says:

It isn't clear to me whether the phrase "typical residential non-simultaneous" implies that "non-simultaneous" is what is typical. (It could also mean that there are two typical types of water heaters - typical simultaneous and typical non-simultaneous.)

Probably more than you wanted to know:
http://waterheatertimer.org/How-it-works.html

From that page, specific to your question:

Electric water heaters are non-simultaneous
Residential 240 volt 2-element electric water heaters are non-simultaneous, as can be seen on product label located on side of tank.
This means both elements are never ON at same time (simultaneously) unless specific wiring inside heater is changed significantly. One element is ON, or the other element is ON, or both elements are OFF.

Upper thermostat is main controller.
Starting with a cold tank, upper thermostat turns on upper element until top 2/3 of tank reaches temperature setting.
After top of tank is heated, upper thermostat turns-off upper element and sends power to lower thermostat which turns on lower element. Lower element runs until tank reaches temperature setting. Lower element turns on-and-off during standby hours to keep tank temperature at thermostat set point.

[Ron Citerone]

Never thought about it or knew this. That’s why I love this forum. Intersesting stuff.

[Dave Zellers]

Never thought about it or knew this. That’s why I love this forum. Intersesting stuff.

A big +1 on that.