I have a GE "SmartWater" Model #GE50M6A It only has 120 volts on the lower element. It is not heating water, but does have 240 volts to the upper element and, as I stated, 120v to the lower element.

Push circuit breaker fully off and then fully ON
Test for 240 volt across top twp screws on upper thermostat.
If tank was not full of water when breaker was turned on, then upper element burned out.
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html#new

Yes both elements will test for 120 volt to ground at all times... but it takes 240 volt to heat element
http://waterheatertimer.org/Element-tests-for-120-Volts.html

Gene


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Test across top two screws on upper thermostat for 240 Volt
Press reset button located on upper thermostat
Reset circuit breaker
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html#new

http://waterheatertimer.org/images/Upper-thermostat-w-wire-a-2.jpg

Otherwise elements will test 120 Volt to ground at all times.
http://waterheatertimer.org/See-inside-main-breaker-box.html#main

http://waterheatertimer.org/How-to-reset-circuit-breaker.html

Gene

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

top element fried unless temp was met at time of test

If your top element is bad the the lower element will never turn on be cause the top element completes the 240 circuit. It is like a resister in a circuit. Make sure top element measures out at 13 ohms.

Open following links to get started.
If water heater has NO hot water, then best suspect is ECO reset button tripped on upper thermostat. Open upper cover and push in red reset button. If reset keeps tripping, I usually replace both upper and lower thermostat.

If water heater has some hot water, then upper element is good so test lower element.
http://waterheatertimer.org/How-to-test-water-heater-element.html
http://waterheatertimer.org/How-to-replace-water-heater-element.html
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html

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It sounds like upper or lower thermostat.
Thermostats turn off one leg (or one wire) in the 240Volt circuit, so each elements will test for 120V even when thermostat is off.
When thermostat turns ON, it closes circuit by adding the second leg to 240V circuit, and element turns ON.
http://waterheatertimer.org/How-to-wire-EH40-hot-water-heater-timer.html#120-240
http://waterheatertimer.org/How-water-heater-thermostat-works.html

Take 30 minutes and troubleshoot before replacing parts:
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html

Your water heater has 2 elements so its 240Volts.

1) If breaker is delivering power on one leg of the 240Volt circuit, then water heater can appear to have electricity, but tank is receiving 120V. Both 120Volt legs are needed to complete the 240V circuit. Double check for 240Volts.

2) Review electric Load.
Water heater label shows wattage of tank.
If tank is 4500Watts for example, you installed 3500 or 4500 watt elements.
With 5500 Watt elements you need 30 amp breaker and orange-colored 10 gauge wire
With 4500 Watt elements you can get by on 20 amp breaker and 12 gauge wire up to 75 feet away.

3) Check ECO red reset button on upper thermostat. If reset is tripped, then ECO is reading high temperatures. Suspects at this point are defective upper thermostat, shorted wire or bad lower element.

4) Also note that insulation and cover must be re-installed over thermostat. Thermostat reads temperature through wall of tank. If outside air circulates around thermostat, that can cause a mis-read and cause tank to overheat and ECO trips.

If you don't want to test the heater, replace both thermostats for about $25. Return the upper thermostat for a refund. Then see of problem persists.

Here's what I would do.
1. Check breaker for 240
2. Check water heater for 240 across 1 and 3 screws on upper thermostat
3. Note wiring and breaker size.
4. Note label on side of tank.

5. Look at end of new element to see wattage printed on each element. Look for sings of high heat and burning. Tighten screws on elements.

6. Check ECO reset button. Look for high-heat and burning. Tighten screws on thermostat.

7. Test upper thermostat as follows:
http://waterheatertimer.org/images/Electric-diagram-water-800.jpg
Test left-side #1 screw to right-side middle #4 screw. Test should read 240V at all times. If not, then ECO is tripped, thermostat is bad, or electricity is OFF

8) Water heater is cold so upper element should be ON. Test upper thermostat.
Test right-side #3 screw to left-side bottom #2 screw and it should read 240V
Test right-side #3 screw to right-side bottom #4 screw and it should read 0 volts

8. If upper thermostat checks out. Test upper element for 240 across both screws. If upper element does not read 240 when water is cold, then element is bad or there is a shorted wire between element and upper thermostat.
How to test element:
http://waterheatertimer.org/How-to-test-water-heater-element.html

9. Do a full troubleshoot on electric water heater
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html

The controls of electric water heaters are designed so that at no time are both the top and bottom heating elements energized. Nearly all electric water heaters of this capacity in the US & Canada (other places, too) operate on 240 Volts.

When the water in the tank is below the set point of the thermostat (in your case - 120 degrees), the top heating element is expected to be on - (unless there is an issue with the top thermostat or limit switch). The top most control is the "high temperature limit". It is identified by the reset button on it. Make sure this isn't tripped by depressing the button. If it clicks - it was tripped and should start to make hot water at this point. If not tripped, you should check for the presence of 240 Volts between the heating element terminal screws. Do not measure from ground to a terminal screw and believe 120 Volts is "good". To make heat, you need 240 Volts - not 120 Volts measured across the terminals - not to ground. The amount of heat created running at 120 Volts is only 1/4 of what it will do at the correct voltage.

If you don't measure 240 Volts on the top element, check the bottom element in the same manner described for the top element.

If unable to measure 240 volts on any element, either there is a problem with the power source (blown fuse or circuit breaker), high temp limit switch, or thermostat(s).

If 240 Volts is present on either heating element, and water is not warm / hot in 30 minutes or so, a defective heating element is suspect. You can change controls without draining a tank, but replacing elements will require draining the tank first. Do not power the water heater without first filling it.

You can read a very detailed "how to" article about checking water heaters here.

I hope this helps - and good luck!

change the thermostat on both upper and lower elements, and the elements depending on the age of the water heater, if it is over 6 years old consider changing the water heater,

If the water does not heat, then you have to troubleshoot to find the problem. With a voltmeter determine if 240VAC is actually getting to the water heater. Take care here - a defective circuit breaker can give a false 240 volt reading - check for the 240 volts across the upper element (i.e. when the 240 volts has a live load on it, not just an open circuit test).
Also, remember, the upper element has priority over the lower element, and if the water is cold, the upper element will try to turn on and this locks out the lower element (only one element is allowed to heat at any given time). The lower element comes on ONLY after the upper thermostat is satisfied. Therefore if the upper heating element is burned out you will never get any hot water. If you suspect this, TURN OFF THE POWER TO THE HEATER and take a resistance check of the upper element.