# Electric heater element



## Leach713 (Nov 1, 2013)

Quick question for you old timers

How quick does it take for a heater element to burn out when turning the water heater on with our water? 

Another one, can a element getting low voltage burn out an element per say?


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## plumber11928 (Feb 18, 2015)

When you dry fire an element it melts in a matter of seconds.
I don't think low voltage would burn one out.
not enough voltage and the element might not get hot enough.


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## tim666 (Mar 11, 2014)

"Old timers", it's a big world out there, electric water heaters are the most popular heater here. We only started getting gas about 5+ years ago


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## KoleckeINC (Oct 22, 2011)

Seconds...an ohmmeter can be used to test it with the wires disconnected and the friendly folks when you call the 1800# on the side of the tank will tell you what it's sposed to read.


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## Redwood (Sep 8, 2008)

Well interesting question and the answer could be as varied as, "It will burn out instantly," all the way to, "It won't burn out."

The big variable is the "Watt Density" of the element.

Take your 4500 watt element and in the "High Watt Density" configuration you'll have a single loop a little over a foot long. Figure if you straightened it out the element might be all of 30" long so there is basically about 150 watts per inch and you'll have a pretty hot element which will burn out quickly if not cooled by water.

Now lets look at the same 4500 watts in a "Low Watt Density" configuration where there are 2 loops instead and if you straightened out the element it would be about 60" long. Now you have about 75 watts per inch and the element while still putting the same 4500 watts of heating into the water will be a much cooler element and if dry fired will be slower to burn out...

Finally lets look at the same 4500 watts in an "Ultra-Low Watt Density" configuration where even more length has been added by a zig-zag bend shape so the actual length of the element straightened might be 90" in length and yield about 50 watts per inch. These will be by far to coolest operating element while still providing the full 4500 watts of heating into the water. Claims are made that these will not burn out even when dry fired, but I wouldn't tempt fate...

You can read more about them as well as see pictures here...


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## MACPLUMB777 (Jun 18, 2008)

I have seen dry fired elements last from a couple weeks to a month then fail,
you can usually tell by a burn hole when you remove the element or other
signs that show that the element was overheated :whistling2:


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## KoleckeINC (Oct 22, 2011)

That's why a resistance test is all that's necessary.


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## Gargalaxy (Aug 14, 2013)

Off topic for a minute, welcome back leach.


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## Leach713 (Nov 1, 2013)

Thank you I been busy trying to learn this umm thing you call plumbing heh


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## Redwood (Sep 8, 2008)

KoleckeINC said:


> Seconds...an ohmmeter can be used to test it with the wires disconnected and the friendly folks when you call the 1800# on the side of the tank will tell you what it's sposed to read.


Using some basic electrical formulas will tell you what the resistance should read...

Wattage / Voltage = Amperage

4500 watts / 240 volts = 18.75 amps

then

Voltage / Amperage = Resistance in Ohms

240 volts / 18.75 amps = 12.8 ohms

Therefore the resistance of a 240 volt 4500 watt element should read 12.8 ohms on your meter...


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## PLUMBER_BILL (Oct 23, 2009)

Leach713 said:


> Quick question for you old timers
> 
> How quick does it take for a heater element to burn out when turning the water heater on with our water?
> 
> Another one, can a element getting low voltage burn out an element per say?


Lots of talk on this back a couple of years, but again Mr. OHM is mentioned go into search then tag search look at a couple of those posts.

In the search box type water heater repairs


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## Plumbducky (Jun 12, 2010)

Installed an electric water heater on a commercial project a few weeks ago. Stopped in to see if the water was on.

It was and so was the electric to to water heater. Mind you the heater was empty. The dumb electrician fried the element and now I have to repair a brand new water heater that has no water in it.


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## KoleckeINC (Oct 22, 2011)

Plumbducky said:


> Installed an electric water heater on a commercial project a few weeks ago. Stopped in to see if the water was on. It was and so was the electric to to water heater. Mind you the heater was empty. The dumb electrician fried the element and now I have to repair a brand new water heater that has no water in it.


Sounds like you got Plumb lucky! Double charge!


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