How to Check the Electrical Wires to the Hot Water Heater

Use a multimeter to check electric hot water heater wires.

Water heaters have several wires and connections that can fail at any point. As you check the wires on the water heater, make sure that all the wire connections are tight. Checking the electrical wires to the hot water heater requires checking some of the connections while the electricity is on. If you do not feel comfortable working with live electricity, contact an electrician rather than attempting this yourself.

Things You'll Need

• Phillips screwdriver
• Slotted screwdriver
• Multimeter

Instructions

1. Turn the 30-amp double-pole breaker off inside the main circuit panel. This stops the flow of electricity to the water heater.

2. Remove the screws from the access panel on the side of the water heater to expose the thermostat and heating element. Some water heaters have two access panels with two thermostats and elements. Loosen the two terminal screws on the heating element to remove the wires from beneath them.

3. Set the dial on a multimeter to resistance times 1,000 ohms (Rx1). Touch one probe from the multimeter to one terminal screw and touch the remaining probe to the remaining terminal screw. The multimeter needle should move all the way to the right if the element is still good. Reattach the wires to the heating element if the element is still good. Replace the element if you do not get a reading on the meter.

4. Remove the plastic thermostat cover from the water heater thermostat. Use a slotted screwdriver to set the thermostat to the highest setting. If your water heater has two thermostats, set the lower thermostat to the lowest setting.

5. Turn the dial on the multimeter to 250 alternating current (AC) and turn the 30-amp double-pole breaker on at the circuit panel, powering the water heater. Find the two wires attached to the two terminal screws above the red reset button on the thermostat. Touch one probe from the multimeter to one wire and the other probe to the remaining wire. The multimeter needle should register between 220 and 240 if the wiring is supplying power to the thermostat.

6. Touch both multimeter probes to each wire on the element below the thermostat. The meter needle should read between 220 and 240. If the meter fails to show a reading, you must replace the thermostat.

7. Set the temperature on the upper thermostat to the lowest setting and set the lower thermostat to the highest setting. Place the multimeter probes on the two wires attached to the element. You should get a needle reading on the multimeter between 220 and 240. If you do not get a reading, check the wiring on the lower thermostat.

8. Touch one probe from the multimeter to the upper wire on the lower thermostat and the other probe should touch the metal of the water tank. Your meter needle should register between 110 and 120. No reading means the upper thermostat is not sending electricity through the wires to the lower thermostat and the upper thermostat needs to be replaced. If you have power, touch one prong of the meter to the lower wire on the lower thermostat and the other prong should touch the metal on the water heater. Your needle should register between 110 and 120 if the lower thermostat is still good. Replace the lower thermostat if the meter does not register any electrical current.

9. Turn the breaker off and reset the thermostats to 120 degrees F. Replace the plastic thermostat covers and attach the access panels to the water heaters.

10. Remove the electrical access panel at the top of the water heater. Gently pull the red and black wires and their connectors from the water heater to give you room to test them. Verify that the wires are still connected together and the connectors are tight. Turn the water heater breaker back on at the main panel.

11. Place one probe from the multimeter into the wire connector that connects the two red wires together. Touch the remaining probe to the metal of the water heater; your meter needle should register between 110 and 120. Repeat the test for the black wires. If either set of wires fails to read a current, check the wiring at the breaker panel.

12. Turn the water heater breaker off and gently push the water heater wires back into the electrical access. Replace the electrical access panel to the top of the water heater.

13. Turn the main breaker off at the top of the main electrical panel to disconnect the electricity to all the breakers. Remove the main breaker panel cover, exposing all the wiring and the terminal screws at the back of the breakers.

14. Turn the main breaker on to power the main electrical panel. Touch one probe of the multimeter to the red wire terminal screw at the back of the 30-amp double-pole water heater breaker. Touch the remaining probe to the metal of the panel box. Your meter should register between 110 and 120. Repeat the test for the black wire terminal screw. If you do not receive a reading on either test, the breaker is bad and needs to be replaced.

15. Turn the main breaker back off and replace the panel cover. Turn the main breaker back on to supply electricity to the entire panel.

References

• InspectAPedia: How to Test & Replace Bad Electric Water Heater Heating Elements
• Water-Heater-Repair-Guide: Hot Water Heater Thermostat
• Water-Heater-Repair-Guide: How To Use A Multimeter
• "Plumbing 1-2-3"; Steve Cory; 2005