Water heater element tripping Ground Fault

burfurd · 06-17-2011, 09:21 PM

I installed an after market electrical water heater in my motor home recently. The heater worked fine initially and after about 3 weeks, started tripping the GFI on the circuit where the heater was plugged in. The heating element did not check shorted with an ohm meter, it registered about 33 ohms which the should be about normal. I called the company I purchased it from and they agreed to send a replacement unit.

Meanwhile, I tried the heating unit into a non GFI plug and it worked fine. Received the replacement unit and worked fine in the GFI outlet again. Later the same thing started happening after about 3 or 4 weeks. Again, the unit worked fine in a non GFI outlet.

Drove the motor home back to TN from FL where we spent the winter and after a few weeks, went camping again....GUESS WHAT? The heater works again connected to the GFI outlet for about a week and then again, starts tripping the outlet. What is going on?

I know I can just change the outlet to a non GFI but would really like to understand what is going on. The heating element will trip a GFI plugged directly into an outlet with no other electronics in the circuit. This makes 2 heaters that have done exactly the same thing. I even tried a different GFI circuit outlet.....Same thing!

burfurd

**RV Wizard** · 06-18-2011, 03:11 AM

The heating element has a current leakage to ground. The GFCI monitors the current traveling on the hot and neutral conductors and if more than 5 milliamps difference the circuit is interrupted. On a non GFCI protected circuit the breaker will not trip out until it basically has a dead short. As long as the circuit does not have a dead short the same heating element will work on a conventional circuit breaker. However, if the filament of the element touches the case some current is diverted and the GFCI sees a potential hazard and opens the circuit to prevent electrocution.

wa8yxm · 06-18-2011, 10:35 AM

Let me guess, You measured the element resistance from one of it's terminals to the other.

Did you check for resistance from either of those terminals to GROUND? should be infinity. Bet it's not.

burfurd · 06-18-2011, 10:50 AM

You are correct, I did measure the 33 ohm's across the element. The resistance from each lead to ground is approximately 1.3 Meg-ohms. I say approximately as the element leads seem to be charging up as a capacitor would. The resistance keeps climbing the longer you hold the ohmmeter to the leads. Used Fluke 73III meter.

Guess the fix is to hook up to a non GFI circuit.

Burfurd

wa8yxm · 06-18-2011, 01:39 PM

Well, 1.3 Meg's DC resistance (Assuming it's an AC circuit) may actually be LESS in AC but let's look at 1.2 megs (To make the math easier) and 120 volts.

I=E/R So I = 120/1200,000 or 1/1,000 amp 1 MA. I'm not sure what the trip current is on a GFCI off hand but that sounds about right, I know I can feel 5MA. or less.

**RV Wizard** · 06-19-2011, 03:36 AM

Did you check the coach with the refrigerator unplugged? You could have a problem with this element. If it also check OK then the problem is going to be when the element is heating, that the filament may move inside the ceramic insulator inside the steel jacket to the pint of making contact with the grounded jacket. Trust us, replace the element and you will find the coach does not trip the GFCI breaker.

burfurd · 06-19-2011, 07:13 PM

I have replaced the element. This is the 2nd one that has done the exact same thing. The elements work fine in the GFI circuit for a few weeks and then start tripping it. Both did the same thing. If I leave the element unplugged for several weeks, it will work fine again for a few days in the GFI circuit and then start tripping again. This is the weird part.

I just use an adapter and plug it into the 30 or 50 amp circuit and it works fine.

The refrigerator heaters are NOT on this GFI circuit. I have 2 GFI's in the coach and this one only goes to the engine heater, bathrooms and outside plug in the basement.

burfurd

ralper · 06-19-2011, 07:27 PM

I would guess that the elements were made in China ?
Many times in my plumbing and heating career I have had two new bad parts in a row on the same repair. I had three oil burner controls that were bad right off the shelf one time. Fortunately these were few and far between.

tvman44 · 06-19-2011, 08:40 PM

You definitely have either a bad GFCI receptacle or some leakage somewhere, it could very well be in the wiring and not the element. If you want to trial and error it change the element and the GFCI receptacle they are not very expensive and if that does not fix it then you will have to look at all the wiring. HTH.

burfurd · 06-20-2011, 06:42 AM

I have eliminated all except the heating element. As the heating element is 115 v. I hooked it directly to a zip cord and plugged it directly into several GFCI outlets. It tripped each one the same. The outlet in the coach never trips when the heating element is NOT plugged into it.

I just can't understand why it will trip and then when left off for a couple of weeks will NOT trip the same GFCI outlet. Just doesn't make any sense.

The heck with it, i will just run a non GFCI outlet into the closet behind the water heater and install a switch so I can turn it on /off as needed.

Probably is made in China as almost everything else is (at least the parts to make up the whole)!

burfurd

burfurd · 06-20-2011, 09:13 AM

I got on the company's website that I purchased the unit from and ran across this in the faq area. Think this may be the problem.

Q:I installed my Lightning Rod and it worked well for maybe 1.5 years. Then it started tripping the circuit breaker after being on for an hour or more. I would reset the breaker and it would work right away but trip again hours later. I think it is a problem in the thermostat when it click off. I tried a different breaker and it was the same story. I checked all my connections and they seem ok. I would like to buy a replacement thermostat and try it. How can I order a replacement thermostat?

A: I would suspect that the problem is the heat element. Have you taken the rod out yet and inspected it? If it looks ok with no split open casing you might want to test the two white wires with an ohm meter. The 6 gallon heat elements are 33 ohms (+ or - 4 ohms). The ten gallon heat elements are 22 ohms (again, + or - 4 ohms). If you are tripping a ground fault type breaker (the ones with a "test" & "reset" button on them), you can take the heat element to a warm & dry spot and let it set for a couple of days. A good place to place the rod is on a heat register in your house. What we believe is happening is that latent moisture in the air has collected in the heat element and the ground fault breaker is picking up very slight arcing to ground. If you were to connect the Lightning Rod kit on a non ground fault breaker (standard type breaker) and run it for a couple of days also, that might be all you need to do and then switch back to the ground fault you are connected to now. After you thoroughly dry it out and it is working like it used to, We would suggest removing the rod and applying a drop or two of super glue liquid to each white wire right where it enters the heat element. Leave it propped up with wires going up until it dries. We have found that the teflon button (where the wires exit the rod) does not hold out water or even moisture in the air after a year or two. We now completely dry out each heat element we purchase and add our own clear sealant to this area. Just do not add the super glue until you completely dry it out otherwise you will seal in the moisture and it will never work with a ground fault breaker.

Hope this helps someone else who has had this problem.

By the way, the unit is made in the USA according to their website.

burfurd