Electric Water Heater Won’t Heat? 5 Probable Causes

Home » Electric Water Heater Won’t Heat? 5 Probable Causes

A steady supply of hot water in the home is a convenience we don’t want to be without. While having to heat buckets of water on a stovetop to wash dishes or fill a bathtub may hold some rustic appeal, that’s no substitute for a fully functioning hot water heater. Earlier this year, Repair Clinic addressed how to fix a broken gas water heater. The article you’re reading right now is all about how an electric water heater works, troubleshooting why the water heater won’t heat, and how you can fix the water heater yourself.

How an electric water heater works

How does an electric water heater work? Most electric water heaters use two heating elements to warm the water in the tank. When a designated water temperature is reached, the heating elements will cycle off. The lowest available temperature setting will rarely cycle the heating elements on; the highest available setting is usually around 150 degrees Fahrenheit (or 66 degrees Celsius). Is there a recommended temperature setting? Yes, most manufacturers recommend that the water temperature be set no higher than 120 degrees Fahrenheit (or 49 degrees Celsius). The efficiency of the water heater is dependent on both the tank and the heating elements.

Understanding how your home’s plumbing connects to the water heater tank

Both the incoming cold water pipe and the outgoing hot water pipe connect to galvanized steel pipes on the tank. Since many homes have copper plumbing, a dielectric union is needed to connect the two types of piping. Without this union, the pipes can deteriorate due to electrolytic corrosion, a process that occurs when water flows across two dissimilar metals.

The incoming cold water pipe attaches to a dip tube that extends into the tank from the top to near the bottom. By having the dip tube placed this low in the tank, the freshwater entering the tank can be heated evenly by the two heating elements.

The interior of the water heater tank is coated with enamel for protection

Although the interior of the water heater tank is metal, it’s coated with enamel which helps prevent chemicals, salt, and other minerals from attacking the metal. To further protect the tank and dip tube, an anode rod is used to attract corrosive minerals. Some water sources, such as well water, will attack the anode rod which can result in a strong sulfur smell. However, removing the anode rod is not recommended since the corrosive minerals the rod attracts can quickly deteriorate the tank and cause it to fail.

Why a water heater tank has three water valves

Water heaters will normally have three water valves: a shut-off valve attached to the incoming cold water pipe, a drain valve near the bottom of the tank, and a temperature and pressure relief valve near the top.

As mentioned earlier, mineral deposits can collect in the tank over time. To avoid deposit build-up, the drain valve can be opened to flush out old water that contains these mineral deposits. How often should this be done? Repair Clinic recommends flushing out all of the water from the tank once every few years. However, if your home uses well water (which contains more minerals than a municipal water supply), you may want to do this more frequently.

If the water temperature or pressure increases above proper operating levels, that’s when the temperature and pressure relief valve goes into action, automatically opening to release steam and water to stabilize the system. A discharge tube is required to be installed on the valve and positioned six inches from the floor to prevent scalding water from spraying out of the tank and causing injury.

How the heating elements heat the water

Most electric water heaters use 240 volts of alternating current to operate the two heating elements, one of which is located near the middle of the tank while the other is located near the bottom. Since the dip tube distributes the freshwater near the bottom of the tank, the location of the two heating elements is ideal for heating the cold incoming water. Each heating 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 on one at a time, and the frequency of these cycles depends on how much heat is needed.

The 5 probable causes of your electric water heater not heating

What can you do if your electric water heater is not heating the water as expected? Repair Clinic recommends looking into these five potential causes:

  1. Blown fuse or tripped breaker – Before you do anything else, check to see if a house fuse has blown or a circuit breaker has tripped. A blown fuse or tripped breaker will prevent voltage from reaching the water heater, and without voltage, the water heater won’t heat.
  2. Tripped thermostat reset button – It’s also possible that the reset button on the water heater’s high-limit thermostat (this one is usually located near the upper heating element) has tripped. Press the button to reset the thermostat to see if that solves the heating problem.
  3. Malfunctioning heating element – If one or both of the heating elements are malfunctioning, the water won’t be heated properly. You can determine if a heating element is defective by using a multimeter to test the element for electrical continuity – a continuous electrical path present in the part. If the heating element tests “negative” for electrical continuity, you know the component is bad and you’ll need to replace it with a new heating element.
  4. Faulty thermostat – Since each of the heating elements is controlled by its own thermostat, a faulty thermostat may prevent voltage from reaching the element to cycle it on. Again, you should first check to see if the high-limit thermostat reset button has tripped. As with the heating element, you can use a multimeter to test the thermostats for electrical continuity to determine if one or both need to be replaced.
  5. Broken dip tube – As noted earlier, the dip tube is attached to the incoming cold water pipe to distribute the freshwater towards the bottom of the tank to ensure that water will be heated evenly. If the dip tube deteriorates and breaks, the incoming cold water will stay near the top of the tank where it won’t heat properly. To determine if a broken dip tube is the cause of the water heating problem, you will need to close the valve to shut off the cold water supply to the water heater then open the drain valve to drain a small amount of water from the tank (just enough to lower the water level a few inches from the top of the tank). Next, detach the incoming cold water pipe from the dielectric union and you should be able to uninstall the dip tube by pulling it out from the top of the tank. If the tube has become completely detached or shows signs of damage, you’ll know you need to install a new one.

Learn how to fix your water heater with Repair Clinic

Want more information on how you can fix a water heater yourself? Visit Repair Clinic.com’s “Videos & Articles” content library to view instructional videos such as “How A Water Heater Temperature & Pressure Relief Valve Works” and “How To Replace An Anode Rod” on an A.O. Smith electric water heater (model ECS40200). You’ll also find model-specific schematics, diagrams, and step-by-step repair guides to assist you; just enter the water heater’s full model number in the search bar.

Choose only genuine OEM parts when fixing your water heater

Whether you need a new heating element, thermostat, dip tube, anode rod, or any other component to fix your water heater, make sure you purchase a genuine OEM part. Repair Clinic makes this part easy because genuine OEM parts are all we stock, direct from such manufacturers as Rheem, A.O. Smith, Bradford White, Bryant, Carrier, Coleman, Honeywell, and Lennox. To find the specific component that matches your water heater, enter the full model number of the unit in Repair Clinic’s “Search Parts Online & Get Answers” search bar. You can then use the “Part Category” and “Part Title” navigation filters to identify the exact part you need.

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