Electric water heater elements in Portland, OR homes usually fail from age, from sediment burying the lower element, or from dry firing, which happens when power is restored before a tank is full. Portland's soft Bull Run water is gentle on elements, so many last years, but failures still happen. With the breaker off and confirmed dead, a multimeter test of each element's resistance and continuity identifies the bad one. Replacing an element is a modest repair on a dry tank.
Electric tanks are common in condos and townhomes, such as buildings near Tom McCall Waterfront Park, and in homes without gas service. Their two elements and two thermostats handle all the heating.
How an electric tank heats
The upper thermostat controls the upper element first, heating the top of the tank. Once satisfied, it switches power to the lower thermostat and element, which heats the rest. Only one element runs at a time in most residential tanks.
Symptoms by part
- No hot water: often an upper element or upper thermostat failure, or a tripped reset.
- Short hot water: often a lower element failure.
- Lukewarm water: thermostat settings or partial failures.
- Tripping breaker: shorted element or wiring.
Why elements fail
- Age: elements wear out over years.
- Sediment: the lower element can be buried and overheat.
- Dry firing: restoring power to an empty tank burns out the upper element almost instantly.
- Voltage issues: loose connections cause heat damage.
Testing safely
Turn off the breaker and verify with a tester that power is off at the element terminals. Remove the access panels and insulation. Disconnect one wire and measure resistance across the element terminals; a typical element shows a resistance consistent with its wattage. Infinite resistance means it is open. Check for continuity between each terminal and the tank to detect a short.
Replacing an element
Drain the tank partly or fully, remove the old element with an element wrench, install a new one with a new gasket, refill completely with a hot faucet open, then restore power. See water heater repair.
When replacement is better
If the tank leaks, is rusted at the base, or is past about twelve years, consider water heater replacement. A heat pump tank may lower electricity use; see the heat pump guide.
Related
Flush sediment to protect elements; see the hard water guide. Incentives for efficient electric water heating are listed by Energy Trust of Oregon.
A condo example
In a downtown condo, the owner notices hot water running out halfway through a shower. The breaker is fine and the reset has not tripped. With power verified off, a multimeter test shows the upper element reads normal resistance, but the lower element reads open. Replacing the lower element restores full capacity. Because the tank is only six years old and dry at the base, the repair is clearly worth doing.
Common mistakes
- Testing elements with power still on.
- Restoring power before the tank is full, which ruins a new element.
- Replacing an element without a new gasket.
- Ignoring a scorched wire or terminal, which will cause the new element to fail.
- Buying the wrong wattage or voltage element.
Choosing the right element
Match the voltage and wattage printed on the old element or rating plate. Low-watt-density elements may last longer in sediment-prone tanks. Screw-in elements are most common in newer tanks; some older tanks use flanged elements.
Thermostats
If both elements test good, test the thermostats. A failed upper thermostat can leave the lower element without power, or keep the upper element on too long. Replace thermostats in pairs on older tanks.
Resetting the high-limit switch
The red reset button above the upper thermostat is a high-limit switch. It trips when water gets too hot. Pressing it may restore heat, but a trip always has a cause, often a stuck thermostat or a grounded element. If it trips again within days, the underlying part needs replacing rather than another reset.