Thank you for the videos and literature online to learn more about electrical safety within and while using the RV and unknown outlets; it is amazing information indeed.
So here’s what’s happening. Any hot-skin voltage needs two conditions. First, there has to be a source of the leakage current, which obviously is coming from your refrigerator. But secondly and most importantly, you have to have a broken ground wire somewhere in the circuit path back to the service panel.
That means that in order for any voltage to develop on the RV chassis (skin), you must have a broken or high-resistance connection between the frame of your RV and the ground wire in the outlet you’re plugged into. Here’s a diagram of how the power comes into the campground service panel from the transformer on the pole. You’ll see that there’s a pair of hot lines that supply the 120-volt power, as well as a neutral wire for the return current and an EGC/Ground wire for any fault currents.
Next, this is what your RV’s grounding is supposed to look like inside. Note that the incoming EGC/Ground wire is bonded (connected) to the chassis of the RV. And I’ve also added a leakage current between one of the incoming hot wires and the chassis somewhere. In your case this is coming from some damaged insulation or a pinched wire in your refrigerator. This is where the fault current starts from. And as you can see, it SHOULD go right out the EGC/Ground wire back to the service panel and be shorted to the neutral/ground bond. But that’s obviously not happening in your case. So something is wrong with your ground wire.
So it has to be that you have a loose or corroded or missing ground connection SOMEWHERE. The reason for this statement is that if you DO have a properly connected safety ground (EGC for Equipment Grounding Conductor in the NEC handbook), then it’s impossible for internal leakage currents in your RV to create any significant hot-skin voltage. When I say significant, I mean anything more than 2 or 3 volts in reference to earth ground. Any more voltage than that means you’ve lost your EGC/Ground connection back to the incoming service panel’s Ground-Neutral-Earth bonding point. Small internal leakages from each appliance are quite normal and allowed by both UL and the NEC. But you MUST have a low-resistance EGC/Ground (Safety Ground Wire) to drain these currents away or they will end up as a hot-skin voltage. And that voltage can be deadly to both humans and their pets.
The usual suspects are any extension cords, shore power cords, power adapters, and even the Ground-To-Chassis bonding connection inside of your RV’s circuit breaker panel. But most of the time at home it’s a poor ground in the home outlet itself. I would start with testing your outlet for proper grounding with a basic 3-light tester, then move on to testing each power cord connection for continuity in its ground wire. As noted above, you can’t have any hot-skin voltage on your RV if you have a solid ground connection. Without that ground ANY leakage inside of your RV will electrify the RV skin, and not trip the circuit breaker like it’s supposed to do.
Once you have the incoming power sorted out, then you need to measure the skin voltage of your RV. It should be very close to zero volts when measured to earth-ground with a volt-meter.
Now, finally you can figure where the leakage current is coming from in your RV’s refrigerator. What I do is put a clamp-ammeter on the return ground wire, then start disconnecting things one at a time until the leakage current stops. It’s most likely a wire in your refrigerator with the insulation damaged from heat or vibration, and replacing the offending part will correct the fault current. But again, the really important thing is to make sure you have a solid ground wire for your RV so that leakage current can never turn into a dangerous hot-skin voltage.
Let’s play safe out there….
Mike Sokol is an electrical and professional sound expert with 40 years in the industry. Visit NoShockZone.org for more electrical safety tips. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.