For what it's worth, there is no approved continuous leakage to ground in AC appliances. Televisions and inverters sometimes have small value condensers connected to ground that will pass a tiny current. GFCIs are designed to trip if there is an unbalance in the current in the black and white leads. This is so that they will trip even if the current is running to earth.
I'm Mike Sokol, the writer of the Church Woodbury article quoted at the top of this thread, and author of the www.NoShockZone.org
website about RV electrical safety. I'm getting ready to write some new articles about RV hot skin conditions, and researching misconceptions about how they occur. So much more on this later, but here's the basics.
1) For a hot-skin condition to occur you first need an open or high resistance safety ground connection between the chassis/skin of your RV and the Ground-Neutral-Earth bonding point back at the main electrical service panel. Most of the time it's caused by an open ground wire connection inside a dog-bone or pig-tail adapter, but can also occur from a worn or damaged pedestal outlet, mis-wired home receptacle, or even a broken or non-existent wire in a power feed. I've found RV's with loose grounding screws in their own circuit breaker panel, and at least one of them with a broken ground lug on the back of the shore power twist-lock connector. This safety ground needs to have a very low impedance path all the way back to the entrance service panel (less than 1 ohm total) to meet electrical code standards. And no, a ground rod driven into the earth next to your RV will do little or nothing to actually "ground" your RV since a ground rod can have up to 100 ohms impedance to earth and still be code compliant. The ground rod's job is actually to drain away lightning strike currents and keep the local grid's ground voltage close to earth potential.
2) You need a source of leakage current to electrify the skin of the RV. Now I want to correct the statement made in the quote above. Virtually ALL electrical appliances plugged into a 120-volt outlet will have leakage currents to their own chassis. And that amount of current is regulated by UL and the NEC. An appliance without a grounded plug is limited to a maximum leakage current of 0.75 mA (milli-amperes). You'll find that "ungrounded" appliances such as a crock-pot, iPhone charger, or laptop computer will normally develop a "hot-skin" potential around 60 volts even when everything is operating correctly. But because the current is limited by UL standards to less to 0.75 mA, you'll never feel a shock. Just over 1 mA of 120-volts, 60 Hz AC is the lower threshold of feeling a shock, which is certainly not dangerous. However, appliances with a grounded plug can have a maximum of 3.5 mA of leakage current between the line and chassis and still be within UL guidelines. Normally that 3.5 mA of leakage current is drained away harmlessly by the safety ground path of your RV. But if your RV's safety ground path is compromised, then there's nothing to drain away that leakage current and a hot-skin voltage is the result.
3) Those hot-skin voltages come in two flavors, high-current and low-current. The low-current hot-skin condition can be caused by a single appliance inside your RV with normal leakage currents. This can be a microwave oven, RV battery inverter, refrigerator, television set, or even a computer with a grounded power cord plugged into your RV's 120-volt system. Also note that these appliance leakage currents are additive, so 2 or 3 mA of leakage from your microwave can add to the 2 or 3 mA of leakage from a MOV surge strip (yes, they leak current to the safety ground as well). So it's entirely possible to generate over 5 mA of leakage current to ground which will trip a GFCI 20-amp receptacle on your campsite pedestal.
4) A high-current hot-skin condition is typically caused by a wire inside the walls of your RV being drilled through by a screw, or pinched by a box cover, or even worn through insulation that's hanging on a metal crossbeam. High-current hot skins can easily provide dozens of amps of current, so if you touch an RV with a high-current hot-skin, your body's 1,000 ohm resistance (damp hand to hand or hand to foot) can cause up to 120 mA of shock current to flow through your chest cavity. Note that only 10 mA of 60 Hz current is dangerous to a person with a weak heart and is very painful, 20 mA will cause your muscles to seize to the point where you can't let go of an electrified object, and 30 mA of current through your chest cavity for a few seconds is nearly always fatal without immediate CPR and defibrillation.
So, it's completely possible to trip a GFCI at a 20-amp pedestal outlet and to have nothing specifically wrong with an RV electrical system. It's also possible to generate a 120-volt hot-skin condition from a broken safety ground wire that results from these same high-impedance leakage currents from several of your RV appliances, all of which are operating within UL leakage limits.
A ground rod driven next to your RV can drain away a high-impedance (low-current) hot-skin voltage, but will do NOTHING to stop a low-impedance (high current) hot-skin voltage. And putting your leveling jacks down on the dirt will do nothing to "ground" your RV, contrary to popular belief. And as little as 30-volts AC across wet hands can induce 30 mA of current across your heart and be deadly.
The takeaway is that your should NEVER feel any type of shock from any appliance or RV. If you do feel a shock, then shut it down and unplug immediately and get it checked by a licensed electrician or technician. However, note that there's a lot of electricians and technicians who don't seem to understand what causes shock conditions, so if there's any doubt, measure the hot-skin voltage yourself. Here's an article I wrote on how to test for hot-skin voltages using a simple Non Contact Voltage Tester (NCVT) which you can purchase online or at any big-box store for less than $25 (and many times less than $15). See http://www.noshockzone.org/rv-electrical-safety-part-iv-
–-hot-skin/ for the article.
Please let me know if that makes sense and contact me at email@example.com
with any questions.