While this DIY Repair blog has devoted articles to identify the reasons a gas water heater won’t heat and the proper way to vent a gas water heater, we haven’t spent much time addressing how to repair an electric water heater. This week, we’re taking care of that! Learn how to test an electric water heater thermostat today.
Electric Water Heater Thermostat Troubleshooting
Let’s start with how electric water heaters heat the water. We’ll then show you, step-by-step, how to test a crucial component that determines how successful that heating process will be.
How an electric water heater heats the water
Most electric water heaters use two heating elements to warm the water in the tank. When electric water heater thermostats installed in the tank detect the water temperature has dropped below a designated setting, the heating elements will cycle on, then cycle back off after the water temperature returns to the designated setting. Lower temperature settings will cause the elements to cycle on less frequently whereas higher settings will require the elements to cycle on more frequently. While the highest available temperature setting on electric water heaters is usually 150° Fahrenheit (66° Celsius), most manufacturers, including Rheem, A.O. Smith, Bradford White, Bryant, Carrier, Coleman, Honeywell, and Lennox, recommend the water temperature be set no higher than 120° Fahrenheit (49° Celsius).
Understanding Electric Water Heater Heating Elements
Most electric water heaters use 240 volts of alternating current to operate both the upper heating element, located near the middle of the tank, and the lower heating element, located near the tank’s bottom. Each element is controlled by its own thermostat. The thermostats maintain the water temperature inside the tank by opening and closing contacts that allow voltage to flow to the heating elements. The elements are designed to cycle one at a time and, as noted above, the frequency of these cycles is determined by how much heat is needed.
What do I do if the water heater isn’t heating?
If your electric water heater is not heating the water, you should first determine if a house fuse has blown or a circuit breaker has tripped. If you’ve confirmed the water heater is receiving sufficient voltage, shut off the power to the water heater and check to see if the reset button on the unit’s high-limit thermostat has tripped. This button will trip if the water in the tank has been overheated. This can be caused by the thermostat contacts fusing closed, the thermostat is out of calibration, or by a shorted heating element. If the reset button has tripped, you should press the button and restore power to the water heater to see if that corrects the problem.
Using a Multimeter To Test the Electric Water Heater Element
Is the water heater still failing to heat the water or does that reset button continue to trip? Then your next step is to use a multimeter to test each element and its accompanying thermostat for “continuity” – a continuous electrical path present in the components – or to determine if one of the elements has shorted. If an element or thermostat lacks electrical continuity or an element has shorted, the part is defective and will need to be replaced.
How To Test an Electric Hot Water Heater Element
Testing a heating element is pretty basic. Shut off the power to the unit, remove the appropriate access panel, detach the power wires from the element, then touch one of the meters leads to one of the element’s terminals and the other lead to the second terminal. The meter display should indicate 10 to 30 Ohms of resistance if the element has electrical continuity. To determine if an element has shorted, touch one meter lead to an element terminal, and the second lead to the element nut or the tank itself. If the meter display indicates Ohms of resistance then the element has shorted. Testing an electric water heater thermostat is a little more involved.
Steps To Test an Electric Hot Water Heater Thermostat
Testing the thermostat of an electric water heater is crucial for diagnosing heating issues. Before beginning, ensure safety by shutting off the power to the unit at the breaker panel. Follow these detailed steps to test both the upper and lower thermostats accurately.
Step 1: Prepare for Testing
- Turn Off the Power – Locate your home’s electrical breaker panel and switch off the circuit breaker that supplies power to the water heater. Verify power is off using a non-contact voltage tester.
- Access the Thermostat – Remove the upper access panel using a screwdriver.
- Move Insulation and Protective Cover – Carefully shift any insulation aside to expose the thermostat. Remove the plastic protective cover if present.
Step 2: Reset the Upper Thermostat
- Locate the red reset button on the upper thermostat.
- Press the button to reset it. If it clicks, it was likely tripped.
Step 3: Isolate the Thermostat from the Circuit
- Note the locations of the power wires connected to the thermostat.
- Disconnect the wires to isolate the thermostat from the circuit.
Step 4: Test the Upper Thermostat
- Set your multimeter to the Ohms (Ω) setting.
- Touch one meter lead to a left-side terminal on the reset portion of the thermostat and the other lead to the other left-side terminal.
- The display should show close to zero Ohms, indicating proper electrical continuity.
- Repeat the test on the right-side terminals.
Step 5: Test the Lower Portion of the Upper Thermostat
- Touch one meter lead to the common terminal.
- Touch the second lead to the heating element’s upper terminal.
- If the water temperature is below the set level, the meter should read close to zero Ohms.
- If the water temperature is above the set level, the meter should read no continuity.
- Move the second lead to the heating element’s lower terminal.
- If the water temperature is below the set level, the meter should show no continuity.
- If the water temperature is above the set level, continuity should be present.
Step 6: Test the Lower Thermostat
- Access the Lower Thermostat – Remove the lower access panel and move the insulation aside.
- Disconnect Power Wires – To ensure an accurate reading, isolate the thermostat from the circuit.
- Test for Continuity –
- Touch one meter lead to one thermostat terminal and the second lead to the other terminal.
- If the water temperature is below the set level, the meter should read close to zero Ohms.
- If the water temperature is above the set level, there should be no continuity.
- An opposite reading indicates a defective thermostat that requires replacement.
Step 7: Reassemble and Restore Power
- Reconnect the power wires to their respective terminals.
- Replace the protective covers and realign the insulation.
- Secure the upper and lower access panels back in place.
- Restore power to the water heater at the breaker panel.
Following these steps ensures accurate troubleshooting of your electric water heater’s thermostat, helping you determine whether a replacement is needed to restore proper functionality.
Find the right part to keep the hot water hot at Repair Clinic and test your electric water heater thermostat
Did your electric water heater thermostat troubleshooting reveal a faulty thermostat or heating element? Then you’ll need to find the right thermostat or element that matches your water heater. The Repair Clinic.com website has already correlated all the data to keep this part of the repair process simple. All you have to do is type the full model number of the water heater in the website’s search bar, then use the “Part Category” and “Part Title” navigation filters to select the appropriate water heater part to display the exact genuine OEM component that works with your unit.
As your repair partner, Repair Clinic can assist you in repairing the water heater yourself. Check out the “Videos & Articles” or “Repair Help” website sections to find troubleshooting and part installation videos, step-by-step guides, schematics, diagrams, and articles to help you keep the hot water flowing.