How to test and replace an electric water heater element. Explore the common reasons for the element failure and how to troubleshoot grounded and open element. Types and buying guide.
The electric water heater element is an immersion heater element type that heats water in a tank type heater when energized with electricity. The electrical current that flows through the heating elements is regulated by a safety device, called high limit.
A thermostat is a device that controls the temperature of hot water. The most common electric heaters you will find, like Rheem, AO Smith, Kenmore, GE, Whirlpool usually have two thermostats and two heating elements.
These thermostats are manually adjusted and are designed as surface mounted, for contact with the external portion of the electric heater.
Thanks to the electric water heater element where the electricity is used as a power source for heating, you can install a unit almost anywhere, which is not a case with the gas heaters that depend on the gas line and need proper venting.
Note: The thermostat, heating elements, and internal wiring are factory installed. You should contact a licensed electrician for any electrical work on the heaters. Checking water heater elements is part of your regular maintenance, for keeping the unit in a good working condition.
Most residential electric heaters are non-simultaneous, working on 240 V and with 4500-watt power. "Non-simultaneous" is a term that means that only one electric water heater element, from two, operates at a time.
Simultaneous configuration means that more than one electric heating element is working.
The non-simultaneous electric heaters have a slower recovery rate than simultaneous while simultaneous require greater amperage protection.
Upper and lower heating elements are identical, and the temperature is regulated by the upper and lower thermostat and high limit device.
Electric water heater elements can be different in size, but the most common is 12" (300 mm). The most common shape is U shape, screwed into a designated female threaded connection in the tank.
Some elements are shorter while others are longer. The shorter ones have a wider tube diameter while longer have a narrower diameter, both having the same heating surface.
Quality of the heating elements goes from good to better and best (premium).
The best elements are usually made of nickel and stainless steel and are known as ultra low watt-density elements. They have a lower heat per sq. inch of a surface than the regular elements, and are usually folded back. This allows easy installation, longer life due to the lime build-up resistance and dry-firing protection.
The electrical and wattage rating is indicated at the front of the heating element. Use the same configuration and/or model when replacing the old heating element.
The high limit device is a safety feature; high limit switch disconnects the electrical current when the temperature reaches the unsafe level.
Since the temperature can be adjusted manually, just use a standard screwdriver. Most safety standards do not allow setting a temperature above 120 F.
Both upper and lower electric heating elements are submerged into the water of the water tank, while thermostat and high-limit switch are on the surface.
When the lower thermostat senses that the water temperature at the bottom of the tank is lower than desired or requested, a lower heating element gets the energy and the process of heating starts.
If the lower thermostat senses that the hot water has reached the set temperature, the electric current flow stops.
If more water is used than what the lower heating element can heat, the upper thermostat will sense that the temperature in the upper part of the tank is lower than desired, electrical current energizes the upper heating element and it begins the heating cycle.
If you need an electric water heater that heats water faster than the one you already have, you should consider a heating element with the higher wattage.
If the tank water heater is not fully filled with water and heating elements are exposed to air, even air pockets, within a matter of seconds, dry-firing of the elements occur. The part of the element that was exposed to air becomes very hot resulting in copper sheathing damages - damages beyond repair. Such an element is deformed, can be easily bent while the plastic sleeves get melted.
In order to avoid such a problem, either buy and install a dry-fired heating element and make sure the tank is always full (so the element is fully submerged) before running the heater.
The limescale build-up on the heating elements is the result of combined work of hot water and mineral deposits (especially regions with hard water). Once formed on the heating elements, the limescale acts as the insulator reducing its effectiveness - so less heat is transferred to the water while the elements are exposed to higher temperature, leading it to failure. Regular maintenance, such as cleaning and draining is the key to long life and high performance.
The heating element, when exposed to voltage surge due to lightning or power surge, also leads to failure. The black soot on the element head, melted plastic, swollen or split sheath usually indicate that there was a voltage spike.
Due to water leaking, water can get into the heating element sheath and make it split.
The heating element doesn't show any signs of deformation, but the inner filament is broken. The only way to check it is to test the element for continuity - the element has to be replaced if there is no continuity.
Other reasons for element failure or not working properly can be mechanical stress due to vibration, high and low voltage supply. For example, high voltage can make an element to burn out, while the low voltage will result in low heat delivery.
If hot water is not hot enough that doesn't mean that you have to replace the whole water heater. Good news is that you might have a defected heating element, which is easy to replace and is not expensive to buy. Since there are two electric heating elements, you should check them both just to be sure which one is broken. The element testing procedure should be the first step when troubleshooting the electric unit which doesn't produce hot water.
Checking water heating elements is easy; test the working condition by placing the multimeter clamp on one of the wires (screw) that are connected to the tested element and the other to any metal part of the water heater. You can also use a non-contact voltage tester. Reading should be per specs.
Turn the temperature up on the tested heating element and down on the other one. Now, you want the electric water heater element that you test to activate.
Open up hot water tap so the heater can start working. At the same time, cold water gets into the unit, and the thermostat senses the change in the temperature, and it clicks when it activates.
Your Amp meter indicates if there is a current flow. If there is no flow, then you have a defective electric water heater element, and it needs replacement. Check the other heating element as well.
A safer way is to test the heating element when the unit is turned OFF when no electricity is present in the heater. Turning OFF the breaker inside the electric panel is vital.
After confirming that there is no electricity, loosen the screws on the element and remove the wires.
Position a dial on the multimeter to Ohms, touch one of the element screws with one probe and the other on the other screw. For the 4,500-watt heating element, there should be 12-13 ohms resistance. If it doesn't show any resistance, this condition is called open element - the element is broken and has to be replaced.
If one probe is on the element screw and the other is on the metal part of the heater, and multi-meter show some values, the element is grounded or bad, and should be replaced.
Before replacing a broken element, make sure to use the same flange, gasket, and specs (wattage and voltage) as found on the old one.
After the tank, electric heating elements is the next most vital component in electric-type water heaters, because bad element means no hot water. It is important when replacing one, to buy a heating element that is durable and reliable, resistant to lime scale and dry-firing.
As seen from above, it is not hard to check or replace the element, but professional service is recommended.