Will Electric Water Heaters Flip the Circuit Breaker in Freezing Temperatures?

Circuit Breakers

• Hot water heaters run on 240 volts AC and require a dedicated power circuit. At the house electrical power panel, either a circuit breaker or a fuse disconnects the hot water heater if the appliance draws too much amperage. Blowing a fuse or tripping a breaker in the house electrical panel indicates a serious problem, such as an electrical short. In most cases, when hot water heaters stop working, the energy cutoff switch in the heater itself trips. The safety system controlled by the red "Reset" button trips when water temperature reaches 180 F, preventing steam explosions caused by runaway heating.

The Heater

• Hot water heaters contain two heating elements that run during different parts of the heating cycle. The home's plumbing draws hot water from the top of the tank first. If each use draws only part of the upper supply out, the upper element often heats water well enough that the bottom element never triggers. Colder weather causes more frequent use of the lower element. Frozen pipes block the pressure relief tank outside the water heater that allows water to expand as the tank heats. Increased pressure causes the tank's relief valve to open but does not trip the circuit breaker.

Hidden Problems

• In warm weather when hot water use drops, homeowners might not notice problems with lower heating elements. In colder weather, when normal use draws more water from the tank, the lower part of the heating system runs more often and problems there become more obvious. A short in the lower element's circuit can trip the main circuit breaker repeatedly. If the lower element burns out, resetting the breaker can restart the water heater, since the burned element now draws no current. The hot water heater then supplies only about half the normal hot water volume, because only the top half actually heats.

Thermostats

• Separate thermostats control the duty cycle of each heating element, turning the element on at the lower temperature limit and off when the water temperature reaches the upper limit. Shorted or sticking thermostats cause heating elements to work continuously, heating the water to the safety cutoff threshold of 180 degrees. Normal water temperature should not exceed 120 degrees for households with small children or elderly residents, or 135 degrees for adult households, according to the University of Florida Extension. Replacing the faulty thermostat restores control of the heating elements. The thermostat sensors respond to water temperature in the tank, not to air temperature around the heater.