Even with a thermostat and other safety circuits in place, resistivity damage can influence temperature safety issues.Īn infinity resistance readout tells a heating engineer the element is obsolete. In short, damaged water heater elements are not only electrically unpredictable, but they’re also thermally unpredictable, so much so that the safely regulated water temperature could turn dangerously high. Subsequently, the fluctuating resistance impacts the heat production effect. If, on the other hand, the resistance measurement is more than 20% above or below the continuity norm, as marked on the element’s datasheet, then it’s on its way out. It’s developed an open circuit and requires a replacement part. If the continuity readout indicates “infinity,” which looks a lot like a sideways figure 8, then there’s no debate, the element is damaged. Therefore, employing an accurate continuity measurement device, a digital voltmeter that’s set to the Ohms scale, technicians use the device’s twin probes to carefully monitor element resistivity. That’s a fault that can’t be allowed to develop. Essentially, continuity fluctuations impact the heat produced by the water heater element. As they wear down, the internal resistance of an element alters. Using a resistance varying thermostat, the water heater’s controls vary fluid temperature, so hot water taps and shower heads receive perfectly warmed water. The wattage of the appliance is fixed, and the circuit voltage is also set. Hot water rises, the cool water drops down toward the element, and the cycle repeats. Slipping into the water, convection currents propagate. That thermal energy conducts through an insulating compound and the element casing. Impacted by system wattage, “Ohms Law” and the laws of thermodynamics collide, then heat is generated. Incidentally, electrical resistivity is measured in Ohms.

The electrical resistance of a properly functioning water heater element can be as low as a few dozen Ohms, or it can climb as high as 70-Ohms. For subtler issues, though, it’s a little harder to troubleshoot such circuit quirks. If the water heating component is broken, the instrument’s readout simply indicates an open circuit. It slips out of a tech’s toolkit as a digital voltmeter (DVM), an accurate electronic tester that measures element continuity.

The technology to electrically test a water heating element has been around for ages.

Testing electric water heater element