How to Determine Which Water Heater Element Is Bad?

A multimeter is used to test heater elements

Determine which water heater element is bad using a few simple tools. Electric water heaters often contain multiple elements. As electricity is applied, they produce heat, heating the water around them. Elements can fail due to corrosion, "dry firing" if water flow is interrupted, or sediment build-up. Element failure may be a direct short and trip the circuit breaker, or a gradual process with the heat output decreasing over time. Identify the shorted or reduced output element by measuring the electrical resistance.

Things You'll Need

• Multimeter
• Phillips head screwdriver
• Flat head screwdriver
• Nut driver

Instructions

1. 

   Turn off power and make sure someone else can't turn it back on

   Turn off the power. Most electric water heaters are wired to a separate circuit breaker. If the circuit breaker is located out of your line of sight, move it to the "Off" position and lock the electrical panel, or attach a note to warn others not to restore power. Many water heaters are 230-volt power, and may have two circuit breakers (usually clamped together). Be certain both circuit breakers move to the "Off" position.

2. Access the heater elements. On smaller water heaters, the entire enclosure may lift off after removing sheet metal screws. Larger heaters have panels with sheet metal screws or access doors with latches. Elements are replaceable parts, and manufacturers usually provide access to them in front or on top of the heaters.

3. 

   Heaters are often 230-volt appliances

   Check the voltage at the elements. To ensure the electricity is off, set your multimeter to AC voltage and test for voltage where the wires attach to the heater elements. If voltage is found, do not continue until you can ensure all electricity to the heater is turned off. The presence of voltage at the elements is dangerous.

4. 

   The Ohms symbol

   Disconnect the wires from one element, noting the original location of the wires.

   Set the multimeter to measure Ohms, usually indicated by the capital Omega symbol, "Ω". On a multimeter with multiple Ohms scales, use the single Ohms setting (not "Rx1k" or "Rx1Meg").

   Touch the leads of the multimeter to the two terminals where the wires were connected. Write down the Ohms value for that element. Replace the wires to that element, and repeat this process on the remaining elements.

   Values under 40 Ohms are considered good for elements up to 240-volts. Higher values, up to 200 Ohms, are indications of increased electrical resistance, but replacement is not necessary. Elements with "infinite resistance" or Ohms resistance above 10,000 should be replaced.

Tips & Warnings

• Take a digital picture of the wiring to help restore connections if it is not possible to remove one set of wires at a time.

• Do not remove any heater element until you have checked the manufacturer's repair manual. Instructions specific to the water heater must be followed to avoid damage to the remaining heater elements, including air purging procedures to guard against "dry fire".

• Danger! High voltage is present inside the water heater enclosure. Make certain all power is off before opening or removing access panels, or removing enclosures.

References

• "Trouble Shooting Guide, Series Two Electric Heaters": Bradford White Corporation (PDF)
• "M2 Series Service Manual": Bradford White Corporation (PDF)

Resources

• How to measure resistance with a meter