How to Check Water Heater Power

Solving Hot Water Heater Problems

Checking your water heater power is the first thing you should do if you have an electric hot water heater problem.

Electricity can kill you. If you are not confident in your ability to work with voltage please call a professional.

You will need to know how to use a multimeter.

Most residential electric water heaters use 240 volts. Their are single element water heaters that operate on 120 volts and single element water heaters that operate on 240 volts. Check the label on your water heater for the voltage rating.

Breakers are usually labeled, however, they can be labeled wrong. It's best to shut off all double breakers before removing the access panels on your water heater.

On a 240 volt breaker there will be 120 volts leaving each side of the breaker. These wires will tie into your water heater under a plate on top of the tank. From there the water heater power will enter the limit switch on top of the upper thermostat.

When checking 240 volts, two wires will each carry 120 volts. If one of the wires has lost voltage, you will not get any reading at all.
One of the multimeter probes must be on a ground to read 120 volts. If you do not get a reading when checking 240 volts, always check for 120 volts by placing one probe on a ground. Never touch naked wires.

Common mistakes
Shutting off wrong breaker - Shut off all breakers until you are sure which one powers the water heater.

Using a multimeter that does not work - Always test a meter on an outlet that you know is working.

Touching naked wires - Never touch the end of a wire that has had the insulation stripped from it, even if the power is off.

water heater power

Testing 240 volts
Shut the power off to your water heater. Remove the access panels, the insulation and the plastic covers.

If you don't see any damaged or burned wires, or water leaking you are ready to check the voltage. If you do, make repairs before you turn power back on .

Power enters the thermostat/limit switch on the top two terminals (see pic).

Turn the power back on. Set your multimeter at or above 240 volts AC. Touch each screw head (see pic) with the meter probes.
You should have a reading of 240 volts.

If your not reading 240 volts you have lost voltage where power enters the water heater, at the breaker or somewhere in between.
You could still have 120 volts water heater power coming into the water heater so don't touch any wires. The multimeter can't read it because these terminals are not grounded. Follow the guide below to check for 120 volts.

If you have 240 volts and no hot water check the water heater reset button.

If you have proper voltage, no hot water and the reset button has not tripped you will need to check the water heater thermostat and/or the water heater elements.

checking water heater power

Place one probe on one of the terminals and the other probe on the water heater tank (scratch the tank with the probe to get a good ground) and check your meter for a reading.

water heater problems

Place a meter probe on the other terminal and tank and check the meter.

If you do not have 240 or 120 volts water heater power, check the breaker. If you have 120 but not 240 volts you could have a problem where the power enters the top of the tank.
These wires can get hot and burn into or short out and trip the breaker. Don't forget to shut the power off before checking any wires.

Related links.

This electric water heater troubleshooting guide will walk you through most hot water heater problems.

How hot water heaters work, this page will help you understand how elements and thermostats interact with each other and which element should be heating and when.

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