The Importance of Accurate Testing in Water Heater Element

Blog | December 3rd, 2018

The technology to electrically test a water heating element has been around for ages. It slips out of a tech’s toolkit as a digital voltmeter (DVM), an accurate electronic tester that measures element continuity. If the water heating component is broken, the instrument’s readout simply indicates an open circuit. For subtler issues, though, it’s a little harder to troubleshoot such circuit quirks. 

Observing the Heat Propagation Cycle

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. Incidentally, electrical resistivity is measured in Ohms. Impacted by system wattage, “Ohms Law” and the laws of thermodynamics collide, then heat is generated. That thermal energy conducts through an insulating compound and the element casing. Slipping into the water, convection currents propagate. Hot water rises, the cool water drops down toward the element, and the cycle repeats. 

Accurately Measuring Element Continuity

The wattage of the appliance is fixed, and the circuit voltage is also set. Using a resistance varying thermostat, the water heater’s controls vary fluid temperature, so hot water taps and shower heads receive perfectly warmed water. Only, heater elements accumulate damage. As they wear down, the internal resistance of an element alters. Essentially, continuity fluctuations impact the heat produced by the water heater element. That’s a fault that can’t be allowed to develop. 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. 

Carrying Out Their Monitoring Duties

If the continuity readout indicates “infinity,” which looks a lot like a sideways figure 8, then there’s no debate, the element is damaged. It’s developed an open circuit and requires a replacement part. 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. Subsequently, the fluctuating resistance impacts the heat production effect. 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. Even with a thermostat and other safety circuits in place, resistivity damage can influence temperature safety issues. 

An infinity resistance readout tells a heating engineer the element is obsolete. It’s out of service and needs a replacement part. More dangerously, continuity fluctuations can ripple through electric circuits and cause unpredictable thermal events in a tank’s stored water. With that dangerous risk factor in mind, an accurate and reliable test instrument must be employed when measuring element continuity.

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