Electric Water Heater Elements

jeepinmatt

jeepinmatt

#1 WEBWHEELER
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Joined
Mar 24, 2005
Location
Stanley, NC
Are they all the same? I noticed our hot water wasn't so hot this evening, checked the breaker, good there. Ohm'd the elements, one was 250 ohms, the other 800 ohms. Hit the reset button and it reset and started sizzling. Seems like both should have similar Ohm readings, so I'm guessing one or both is on its way out. The water heater has a 6 year warranty and it's been installed for almost exactly 6 years, go figure.

I plan to replace both elements while I'm at it. We have high iron content in our water. Maybe that has shortened the life, maybe 6 years is normal?
 
They can have bad welds, or brazes, where they connect to the studs and not get a complete connection.
 
jeepinmatt said:
Are they all the same? I noticed our hot water wasn't so hot this evening, checked the breaker, good there. Ohm'd the elements, one was 250 ohms, the other 800 ohms. Hit the reset button and it reset and started sizzling. Seems like both should have similar Ohm readings, so I'm guessing one or both is on its way out. The water heater has a 6 year warranty and it's been installed for almost exactly 6 years, go figure.

I plan to replace both elements while I'm at it. We have high iron content in our water. Maybe that has shortened the life, maybe 6 years is normal?
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You're doing something wrong. You need to disconnect one or both of the element wires before testing resistance, else you will be measuring other things in the circuit. And shut off the breaker for safety, because you can't take a resistance measurement on a live circuit.

The elements should be tens of ohms or less though, depending on the water heater wattage. 250 and 800 ohms is not right, so I think you're measuring something wrong.

A 3500W element for example should be 16 ohms, because R=V^2/P, which is a re-arranging of Ohm's law and the power law.
So (240VAC^2)/3500W=16 ohms, which means you can get the heater element wattage from the water heater label and figure out almost exactly what the resistance you should be seeing on the multimeter if the element is properly functioning.
 
Fabrik8 said:
And shut off the breaker for safety, because you can't take a resistance measurement on a live circuit.
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As my father always told me: "anyone can do it with the power off!"
 
Fabrik8 said:
Shut the power off and take the resistance measurement again, after disconnecting the wires from the heater element terminals. Otherwise you can't trust anything about the measurement.

I'm going to keep repeating that until you do it properly. ;)
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I know the measurement is useless. Last night in my frustration, I didn't consider that I was checking resistance on the entire circuit, not just the element. But anybody can work on it with the power off :flipoff2:
 
You might want to flush your tank while your at it. After years of service they can build up quite a bit of sediment and if it reaches the element it can prematurely destroy it.
 
Bogleparsons said:
You might want to flush your tank while your at it. After years of service they can build up quite a bit of sediment and if it reaches the element it can prematurely destroy it.
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Yeah, planning to do that too.

It was working when I left the house this morning, so I wonder how long it will continue to work?
 
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