Electric water heaters work on a different principle compared with gas or oil-fired water heaters. Because there is no burner, there is no core in the center, and no heat exchanger or venting system is required.
Electric water heaters typically employ two immersion elements that are similar to the elements in a kettle. One is near the top of the tank and the other is near the bottom.
In general, both elements do not work at the same time. (Note: There are some water heaters that have only one element. Also, some water heaters are designed to have both elements on at the same time).
Both elements are thermostatically controlled, and the temperature setting is usually the same on the top and bottom. A high-limit switch, sometimes called the reset button, usually is attached to the upper thermostat on two element heaters, and to the single thermostat under the lower access panel on single element heaters. It’s a safety device that shuts off the power to the elements if either thermostat fails to shut off. It must be manually reset to reactivate, and it is deliberately designed into the safety device to warn of a possible thermostat failure, which could result in an explosion. Most professionals suggest that, if the device has to be reset more than once, an unsafe condition exists and it requires servicing. The thermostats and high limit controls are not normally accessible without removing an access panel and, often, some insulation. If the electric power to the water heater is on, there is a risk in removing these access panels and accessing the thermostats.
There are live electrical connections adjacent to the thermostats. Unless you are comfortable and skilled working with electricity, you should leave these access panels closed. The ASHI Standard does not require us to remove these panels during an inspection.
These elements provide the heat and, for the most part, the water configuration is the same as on a gas or oil system. Cold water is introduced near the bottom of the tank and hot water is drawn off near the top. The cold pipe may enter the top of the tank or the side of the tank near the bottom.
Lower Element Comes on First
When the tank is at rest, it will be filled with hot water. When a hot water faucet is turned on, hot water will be drawn off the top of the tank and cold water introduced at the bottom. This cold water near the bottom of the tank will activate the thermostat for the lower element. The lower element will turn on and heat the incoming cool water. The upper element will still be surrounded with hot water and will be satisfied.
Upper Element Has Priority
If we keep drawing off hot water, the tank will be filled with cool water because the lower heating element will not be able to warm the water quickly enough as it comes in and flows through. Eventually, all of the hot water will be drawn out of the tank and all the water will be cold. At this point, the thermostats for the upper and lower heating elements both will be calling for heat. The upper element has priority and it will shut off the lower element so that it can operate. As previously noted, only one element can work at a time.
Hurry to Get Some Hot Water
The upper element has priority because after the tank has run out of hot water, we want to prepare quickly for the next use of hot water. The upper element heats the water near the top of the tank first because it is the water that will be drawn off first. Once it heats the water in the top part of the tank, the thermostat will be satisfied and the upper element will shut off. The lower element now gets electricity and heats up the water in the lower two-thirds of the tank. If the upper thermostat never reaches the set temperature because of a burned-out upper element, the lower element will never become energized. The tank will remain cold.
Lower Element Works More
Under normal use, the lower element works more often than the upper element, although the upper element has priority. It would be helpful to let clients know whether both elements are in working order.
Can’t Tell Whether One Element is Burned Out
We can’t tell if one element is burned out without doing tests that go beyond the scope of the ASHI Standard inspection. Some helpful clues can be passed on to your client, however. It is common for two-element water heaters to work—but not very well—if the lower element is burned out. When this happens, only about one-third of the normally supplied hot water is produced. Water heater problems are not always related to the elements. Replacement of elements is not a big job and water heaters themselves are not terribly expensive.
Although there are many common conditions related to electric water heathers and gas or oil-fired heaters, for the most part, they are entirely different. Obviously, issues like fuel supply, burner, combustion air and venting systems are not the conditions that will cause concern.
Common conditions that you will need to be aware of include the following:
• Inoperative system (no hot water)
• Inadequate capacity and recovery rate
• Damaged tank
• Inadequate clearance from combustibles
• Poor location
• Low water pressure and flow
• Noisy water heater
• Temperature and pressure relief valve problems
• Unstable or wobbly tank
• Reversed hot or cold piping
• Drain valve problems
In terms of electric water heater wiring, you should be able to recognize the following problems:
• not on dedicated circuit
• not well-secured
• flexible conduit needed for mechanical protection
• loose connections
• open splices
• too close to ducts, pipes, chimneys and others
• too close to edge of studs or joists
• in steel studs without protection
• exposed on walls or ceilings
• exposed in attics
• undersized wire
• improper color coding
• abandoned wire
Home inspectors should be aware of the many issues concerning the electrical supplies to water heaters. The Electrical Module of ASHI@HOME training discusses issues such as wire size and type, fuses and breakers, quality of connections and support. We encourage you to review this module to learn more about addressing electrical issues related to water heaters.
For information about the ASHI@HOME 10-course training program, you can find more information on the ASHI website (http://www.
homeinspector.org/ASHI-HOME-Training-System) or through Carson Dunlop (http://www.carsondunlop.com/Colleges/ASHI/)
or call 800-268-7070, ext. 251.