Why Does My Electric Water Heater Reset Button Keep Tripping?

So the red reset button on your electric water heater keeps popping out and needing to be reset. 
Here’s the most likely problem: The water in your water heater is getting too hot.
When the water temperature in your water heater exceeds 180°, the red reset button (also known as the high-limit switch) trips. This tripping protects you from getting scalded or burned when using hot water in your home.  Then what’s causing the water in your water heater to get so hot?
​The most likely cause is a bad thermostat.
Electric water heaters have a lower and upper thermostat—one for each heating element.
The thermostats are responsible for controlling the heating elements. When the water has cooled off, the thermostats kick on the heating elements to heat the water. And once the water has reached your desired temperature, the thermostats shut off the heating element.
(This is very similar to the way your heating and air conditioning thermostat controls your home HVAC system.)
But these thermostats can go bad. When they do, they sometimes get stuck in the “on” position. This means that that the heating element continues to heat your water, eventually causing the high-limit switch to trip.
The fix: The bad thermostat needs to be replaced. A plumber can use a multimeter to test the thermostats and find out which one is bad.
While a bad thermostat is the most common reason your water heater’s reset button may trip, it’s not the only one. Other common causes include:

• A shorted heating element—It may be that the thermostat is working just fine and shutting off the heating element. But a short in the element is causing it to continue to heat your water.
• Loose wiring—A loose wire in the water heater can generate heat that can cause the high-limit switch to trip.
• Bad high-limit switch—The switch itself may be malfunctioning and tripping when it shouldn’t be.