Water Heater Thermostat
If your looking for water heater thermostat information you can find it all here. How to test or replace a thermostat. How to check the limit switch, adjust the temperature, buyers guide and more.
How a thermostat works
Water heater thermostats are actually very simple devices. They operate off of a bi metal switch located in the back of the thermostat. When the bi medal disk reaches a certain temperature it will pop in or out which ever the case may be and connect or disconnect the power supply to the heating element. This bi metal disk is what you hear clicking when the temperature is turned up or down.
Thermostat and limit switch
The thermostats in this pic are for a duel element 240 volt storage water heater.
The thermostat on the left is the upper or primary thermostat.
The thermostat on the right is the lower or secondary thermostat.
The upper thermostat is mounted onto a limit switch. I have separated
the limit switch and thermostat so you can see each one separately.
This limit switch (top of pic) has a red reset button.
As you can see this thermostat is
very simple.
Power enters the thermostat on the top
left terminal. When the thermostat calls
for heat power is sent to the lower left
terminal which energizes the upper element
When the thermostat is satisfied power is then sent to the upper right terminal and is transferred to the lower thermostat.
This is the lower thermostat.
Power is sent to the top terminal from
the upper thermostat.
If the thermostat calls for heat power will be transferred to the bottom terminal which will energize the lower element.
The thermostat on the right is designed for a single element water heater.
The thermostat on the left is designed for a duel element water heater.
As you can see the single element thermostat only has two terminals on the right side.
Power comes into the top terminal from the main power supply. When the thermostat calls for heat, power is transferred to the lower terminal which energizes the lower element.
Water heater thermostat buyers guide
If your shopping for a water heater thermostat the two things you'll
need to know are the number of elements in the water heater and the
voltage of the water heater ( check the label on your water heater).
If the label is missing from your water heater you can find the voltage written on the end of the water heater element. Common residential duel element water heaters are 240 volts.
The upper thermostat and limit switch are always sold together.
There are more than 50 brands of residential tank type electric water heaters in the U.S., most thermostats are interchangeable, however, read the product description carefully.
If you must replace a thermostat its always a good idea to replace both thermostats at the same time.
You can check thermostat prices on our electric water heater parts page.
Related links
Test a thermostat
How to check a thermostat with the power off. Thermostats can be tested with the power on
or off. You can check the voltage at the element to see if the thermostat is
working if your comfortable working with the power on.
Replace a thermostat
Replacing a thermostat is easy with this step by step guide.
No special tools required.
Water heater reset button
What to do if the reset button pops out.
How to reset your water heater limit switch.
Water heater temperature
How to adjust the temperature on a thermostat. What temperature should
your water heater be.
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