# heating element health



## jted (May 18, 2018)

Just a few words and thoughts about heating element health. Recently like in the past few weeks I replaced my 800 watt heating element because it was tripping GFCI receptacles. While troubleshooting the old element the only thing I knew to check was the resistance of the element. It was reading in the good zone just above 17 ohm's. I checked the resistance of a new element and it was 17.7 ohm's  in a perfect world it should have been 18 ohms  
Using Ohm's law which can be confusing since it has so many ways to find the same values this is the formula that I used and is not confusing at all.  VxV / watts = resistance  120x120/800 = 18 Ohm's that is for a MES 30 " 20070910 old model. 
Just like human health other factors come in to play but checking the resistance is like checking your blood pressure or pulse. A great place to start. I ran the numbers for several other wattage just so you don't have to. With the *power off  *remove the leads to the element and put a lead from the multimeter on each one Turn the meter to the ohm's or omega sign on the meter and read your resistance
1000 watts =14 Ohm's
1200 watts =12 Ohm's
1500 watts = 9.6 Ohms 
If yours is a above or under the the exact number it is not a real bad thing but much more than 10 % you should be prepared to replace your element. In my case Masterbuilt had the best  price at 25.00 delivered for a 800 watt element. 
I still have not figured out why my old element would trip the GFCI but I think it would break down under power.   Jted


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## bdskelly (May 18, 2018)

Great technical info here. Thanks! B


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## johnmeyer (May 18, 2018)

Two things to add to your calculations.

First, many resistive substances change their resistance as they get hot. This is certainly true of incandescent light bulbs. If you measure the cold filament resistance, the V2/R Ohm's Law calculation will not give you the wattage printed on the bulb. The same may, or may not, be true of the heating element.

The second thing is that a multimeter may not be able to detect leakage resistance that is tripping your GFI. This again is due to the real world not always behaving according to Ohm's Law. The problem in this case is that resistance can be a function of voltage. There are lots of examples of this, such as a fluorescent light which, until it is heated at both ends, will not pass any current. However, once the gas inside is ionized by the starter (which was a separate circuit in the old days, where there was a starter can that you sometimes had to replace), the resistance drops dramatically and current can flow.

In the case of the heating element, if some sort of fault has developed, such as an insulation defect, the insulation may still measure as infinite resistance when tested with the few volts applied from the multimeter, but when you apply a high enough voltage, the insulation breaks down and current can flow.

Finally, most multimeter resistance measurements are taken with a small *DC* voltage applied. However, the element is obviously heated with 60 Hz *AC* voltage. As you know, when AC voltage is placed across a transformer, a current is induced in the other side of the transformer via the magnetic field that only exists when voltage is changing and therefore doesn't exist at all when a DC voltage is applied. This induced voltage can cause a current leak that will trip the GFI.


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## jted (May 18, 2018)

John, I do believe the induced voltage does and has caused the leak you spoke of. I would like to know your thoughts on why when external  heat is applied to the element it will not leak enough to trip the GFCI.   Jted


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## johnmeyer (May 19, 2018)

jted said:


> John, I do believe the induced voltage does and has caused the leak you spoke of. I would like to know your thoughts on why when external  heat is applied to the element it will not leak enough to trip the GFCI.   Jted


I am not quite sure what you mean by "when external heat is applied to the element," but if you mean that you can get it to work without tripping the GFI if you pre-heat the element with a hair dryer and then plug in the smoker, that would seem to indicate possible condensation or moisture somewhere inside one of the wiring boxes, or somewhere else where the one of the wires is exposed.


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## jted (May 19, 2018)

John, The induced heat was from a hair dryer. I had this start several years ago and I had thought it might be moisture in the element but after countless hours heating  I thought it would have evaporated. With the GFCI being so sensitive I will probably never definitely pin it down. I am just happy it is fixed.  Jted


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