Open ground

[jcharles]

We are staying at a private campground in door county Wisconsin. Progressive EMS gave an open ground error on the 30 amp pedestal. The pedestal has no breaker to turn on or off, you just plug in. My multimeter shows 0 volts from hot to ground, but correctly shows 120 volts from hot to neutral and 0 volts from neutral to ground. The campground guy plug his tester in with a dogbone and it lit up correctly, no open ground error and said he hasn't had a problem in 18 years, but also said he isn't an electrician. What problems could I have if I bypass the EMS and plug in? When plugged in I tested for hot skin condition on my rv steps and everything was fine. I tested a totally different campsite in a different loop and the multimeter read the same way.

[wmtire]

Originally Posted by jcharles

My multimeter shows 0 volts from hot to ground, .

That is also verifying there is an open ground as you should get voltage from the hot to ground or the hot to neutral. If it is open, then you would also get 0 volts from neutral to ground, the same as if it was closed.

The voltage between the Hot lead at 7 o'clock and W 120-volt, Hot lead and G 120-volt, W and G 0-volt (or very near it)

I would be wary of this campground, as the ground is your safety. The open ground is telling you that there is a break (or non-connection) of the safety ground. You are connecting at your own risk and may or may not see a problem until running stuff.

[wmtire]

Mike Sokol, the guru of hot chassis condition, has a great article on open ground and how it "can" get worse with the appliances you use.

Are "Little" Shocks OK? | No~Shock~Zone

I copied part of it over, and hopefully Mike won't object. He is a participating member here, and helps out an awful lot. Here is an excerpt.

An RV chassis and skin with ANY significant voltage above earth potential (2 volts is max) is proof that you’ve lost your RV’s safety ground connection. Now, by itself an open ground connection won’t cause an RV hot-skin voltage condition, but nearly anything inside your RV plugged into its electrical system will cause some leakage current to the RV chassis-ground. And that leakage will show up as a hot-skin voltage of varying degree. The really dangerous thing is that sometimes those can be high-impedance leakage currents that aren’t particularly dangerous. And that’s when you feel a “little” shock. However, that same “little” current can quickly become low-impedance/high-current leakage in a heartbeat, and that will almost certainly kill you if you touch the RV with wet hands and feet. It’s just a matter of degree, and you never know what that degree is. So any feeling of shocks from your RV or appliance is a warning to turn off the circuit breakers and disconnect the power plug immediately.
If you do have a proper RV safety ground back to the service panel, then it should be impossible to develop more than 1 or 2 volts on your RV skin. It will harmlessly drain away the small currents from normal high-impedance appliance leakage, as well as trip the circuit breaker form huge currents that result from abnormal low-impedance leakage, such as a screw driven through a wire inside your wall.

So if you measure more than 2 volts between the earth and the chassis of your RV there’s a serious problem with your safety ground. This is usually as simple as a broken or loose ground contact on your extension cord or dog-bone adapter, but can also be due to a problem in your campsite pedestal or home power outlet. Old garages are especially dangerous since they can be ungrounded for years without you knowing it, and the first time you plug an RV into it there can be a deadly hot-skin condition. And certainly a worn RV pedestal outlet can have corrosion or loose contacts, and that can cause an RV hot-skin condition.

[jcharles]

Thanks wmtire, we dont have very good internet reception here and I was struggling to find info. That article verifies what I was thinking/looking for. I follow Mike's work and have his book, but unfortunately it is at home. We are using propane th run the fridge and water heater. Trying to avoid using the electrical.

[wmtire]

I am assuming the campground owner is using a circuit tester based on your previous description. These things aren't always the most dependable (as I would trust a multimeter more). It's also possible maybe that his dogbone adapter could have the neutral/ground bonded together or the ground connected to a metal case if it is a homemade type. Just too many real unknowns at this point as to why his shows good...but your EMS and multimeter readings show an open ground.

However, it sounds like you have a full understanding of it all..and I wish ya the best for the weekend.

[CHICKDOE]

it would be interesting to do two little tests.

have campground guy plug his little tester into a 15 amp receptacle in your rv and see how it reads

take your meter to his adapter and see if the integrity of the three leads is correct (no cross connections within the adapter).