Only one element will come on at any one time. This is known as a flip/flop system. On a 240 volt water heater, there will always be 120 volts to both elements. The thermostat will direct the second leg of the 120-volts to the element to complete the 240 volts required to energize the element.
With a dual-element water heater, there are two heat elements – one on the top and one toward the bottom of the tank. Each element has its own thermostat, and only one element runs at a time. The top element turns on first to start the warming process.
The thermostats control the heating elements in the tank, and they must both be set to the same temperature. Electric water heaters use electrical resistance to heat water. The heating elements, controlled by a thermostat, heat water in the tank.
They all have different wattage ratings and can work on either 120 or 240 voltage. Check your state and local codes before starting any project. Follow all safety precautions. Information in this document has been furnished by the North American Retail Hardware Association (NRHA) and associated contributors.
In addition to what everyone else has said generally you should replace both elements at the same time. If one has failed the other probably will soon.
And the upper element always comes on first because hot water exits from the top. The vast majority of water heaters are wired so that only one element at a time can be turned on.
If the unit is powered with the correct voltage, and still does not produce any hot water, the upper heating element has probably burned out. A water heater must be completely full of water before electric power is applied or the upper heating element will burn out (this is called Dry Fire).
Each model water heater is designed for a specific voltage/wattage rated element. The replacement element must be the same voltage and wattage as the element being replaced. Never exceed the nameplate rating on the water heater.
Factors to Consider When Buying a Heating Element
Wattage - The wattage of a heating element is one of the most important factors to consider. This will determine how much heat the element can generate and how quickly it can heat your desired area. Make sure to pick an element with a wattage appropriate for your needs.
When comparing to the 4500 watt model, I find that the 4500 watt model has a Uniform Energy Factor of 0.93, while the 3800 watt model has a Uniform Energy Factor of 0.92. The 4500 watt element is an average of $5.00 a year cheaper than the 3800 unit.
The maximum Department of Energy recommended water heater temperature setting you should never exceed is 140 degrees Fahrenheit. The lowest recommended setting should never be below 120 degrees Fahrenheit.
The EPA recommendation is to always leave your water heater set to 120 degrees. This is both so that the unit loses less energy and also to prevent possible scalding. OSHA, on the other hand, recommends setting your water heater to 140 degrees in order to aid with cleaning and sanitation.
Most electric water heaters above 20 gallons have two thermostats that sense the temperature of the water in both the top and bottom of the tank. The upper thermostat is the boss and always tells the lower thermostat what to do.
Potential damage to the water heater: If the water heater is not designed to handle the reversed flow, it can cause damage to the internal components.
Yes, but experts don't recommend wiring your water heater this way. A 120-volt circuit breaker can't operate with the full power of a 240-volt circuit breaker. At best, you'll get about 25% of the water heater's total power, which isn't very efficient (or warm!) at all.
If your water heater is nearing the end of its life, consider replacing the element. It's usually most cost-effective to replace both elements at the same time, and doing so will still be worth it, as it's often around a tenth of the cost of installing a new water heater.
Higher wattage elements can lead to increased energy consumption, particularly if used inappropriately. A 5500 watt element may heat water faster but might not always be the most efficient choice for your household size. Conversely, a 4500 watt element can be more energy-efficient if your hot water demand is moderate.
To test the element, you must measure its resistance. Switch the multimeter settings to measure resistance and place the nodes on the two screws. A functioning heating element should read between 10 and 30 ohms. The heating element is broken if the meter reads 1 or 0.
Only one element will come on at any one time. This is known as a flip/flop system. On a 240 volt water heater, there will always be 120 volts to both elements. The thermostat will direct the second leg of the 120-volts to the element to complete the 240 volts required to energize the element.
The bottom element always turns on first. Cold water enters the water heater at the bottom via a "dip tube" from the top that directs the cold water to the bottom.
It's important to know the size, length, diameter, and lead length of the heater required. These factors are important for designing heaters and addressing design limitations that may arise, such as maximum allowable watt density for the style or application of the heater.
If it's an average gas water heater it will probably take about an hour to get a tank full of cold water up to temp. If it's an electric water heater it can take several hours depending on the size of the tank. Electric recovery rates are very slow that is why electric water heaters usually have more storage capacity.