Testing the heating element in a water heater


I have a Solar panel connected to the Immersion heater and recently the water temperature has dropped dramatically even with the Immersion heater on. I have removed the element from the heater but would like to test whether the element is working. is there a simple way of doing it? The pipe at the top of the tank seems quite warm but not sure if thats the panel heating it up or the immersion heater. Thanks
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snipped-for-privacy@hotmail.com wrote:

Well it's easy to test if it's open, just use an ohm meter. The resistance on a working heating element will be close to zero ohms.
Someone will correct me if I'm wrong, but I believe a heating element is either good or bad, there is nothing in the middle, it's either burned out, or it's good.
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Actually wouldnt a reading of 0 ohms indicate a short? I thought the way a heating element worked was due to resistance to current flow. You definately dont want infinite resistance, as that indicates and open...but if i remember correctly a good heating element on my dryer, for example runs a few ohms resistance.
Please correct and cite me if im wrong...I could be..
Josh
SMS wrote:

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snipped-for-privacy@hotmail.com wrote:

I'm quite sure "a few ohms resistance" is pretty damn near "close to zero ohms".
Sounds like you guys are in agreement here...
Rob
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trainfan1 wrote:

There is a very large difference between zero ohms and a few ohms, zero ohms would draw an infinite amount of current. The resistance should very low, i.e. around 12 ohms for a 3.8KW element supplied by 240V. I suggest you measure the resistance of the heating element and then calculate the expected amp draw at the applied voltage. The formula is voltage/divided by resistance or I=V/R (I is current). Then find the KW by multiplying the voltage, the current, and the power factor (I would assume .8) and then divide by 1000 or KW=V*I*.8/1000. What you calculate should match the KW rating of the element. If it does not there is a problem. I agree that heating elements usually either work or they don't. I also agree with a previous poster that it is possible to test on a bench by very briefly connecting a 220V or 110V source to test the element. The watchout is that the element will heat up VERY rapidly and can cause an injury, a fire, or burn out the element since it will not be immersed in water.
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trainfan1 wrote:

There is a very large difference between zero ohms and a few ohms, zero ohms would draw an infinite amount of current. The resistance should very low, i.e. around 12 ohms for a 3.8KW element supplied by 240V. I suggest you measure the resistance of the heating element and then calculate the expected amp draw at the applied voltage. The formula is voltage/divided by resistance or I=V/R (I is current). Then find the KW by multiplying the voltage, the current, and the power factor (I would assume .8) and then divide by 1000 or KW=V*I*.8/1000. What you calculate should match the KW rating of the element. If it does not there is a problem. I agree that heating elements usually either work or they don't. I also agree with a previous poster that it is possible to test on a bench by very briefly connecting a 220V or 110V source to test the element. The watchout is that the element will heat up VERY rapidly and can cause an injury, a fire, or burn out the element since it will not be immersed in water.
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If you have an open(no reading across the two terminals) on a VOM the element is dead, you should get a resistance reading, depending upon the wattage of the element. You could also apply 240 volts across the element for about two seconds, and you'll know if its heating. You need to check the thermostat on the heater, and if its a large tank it will have two elements and two thermostats

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