Current ( voltage ) on camper

[Helmut]

I have a problem that somehow worries me and need some expert advice.
On mexican campgrounds it is quite common to find reverse polarity or open ground ( no ground wire ) on your electric hookup.
As i am from germany and in europe reverse polarity does not exist ( you can plug in a socket either way ) the reverse polarity did not bother me so far.
Until today i thought a ground wire is only needed if there is a faulty wiring in something with a f.e. metal housing. I was sure my FourWheelCamped would not have a faulty wiring.
Here is my problem:
Connecting to a socket with reverse polarity and open ground i have 50 V (fifty) on my door handle - ( not the knob but the grip i use to swing myself up in the camper ) - really shocking !! I have felt these shocks on different campgrounds but not as strong as this time, so i started measuring with my voltmeter.
Changing the polarity gets it down to 40V ( fourty ). Grounding by using a earth pin to zero V.
Now this can`t be o.k., somewhere in my 110V system there must be a problem that lets my camper housing get half of the voltage.
Why half the voltage ? And where shall i start looking ?
would be glad for any helpful suggestions, but i will not return to the states the next couple of years as my trip is going to the southern tip of south america and slowly back up.

 

[Vic Harder]

Get yourself one of these - https://www.amazon.com/Gardner-Bender-GTK-2-GVD-3504-Non-Contact/dp/B00ATOYNP0/ref=sr_1_5?ie=UTF8&qid=1541729885&sr=8-5&keywords=ac+voltage+checker

The problem sounds like it is on the campground's side, not yours. Your camper has a "floating" ground, by virtue of the 4 big rubber insulators, also known as "tires". If you want to be super safe, you could hammer a long spike into the ground and run a wire from that to the camper's ground, or even just somewhere on the frame.

I wouldn't do that though unless it was a sturdy wire and it was fused. Why not? Well, in your case, 50V at some unknown current would be available to flow through your camper to ground via that wire. The ground would certainly be safer, and protect you, but if not fused it could burn up the wire and cause a fire.

I carry one of those 3 prong wiring testers, and would not plug in if it indicated faulty wiring. But then I rarely plug in as I am able to keep running with just solar.

What do other folks do with ungrounded circuits?

 

[Old Crow]

Hi, HekMek...

Your post brings to mind this Shocked By My FWC thread from 2015....

.

 

[Helmut]

Thanks Vic, the ground spoke ( earth pin ) is what i did to get to zero volts, i simply didn't expect any voltage on my camper without a proper ground.

Old Crow, this seems to be extremely helpful and i'm glad you showed the link. I wasn't able to find a topic on WTW myself. Will work through this and it does give some peace that other's had the same expierience.

Thank's again to both of you.

 

[jmsokol]

I'm Mike Sokol, the author of the link to the video on hot-skin/stray-voltage. I'll have more time to go into this over the weekend, but briefly you NEVER want to plug your RV into an ungrounded pedestal outlet. That's because virtually everything electrical that's plugged into an outlet has a little bit of leakage to its own chassis ground. The maximum leakage current allowed by each appliance is limited by UL and the NEC, but it can be up to nearly 1mA and still pass inspection. This leakage will tend to bias the chassis to around 1/2 of the line voltage, so a 50-volt stray voltage on an ungrounded RV chassis is perfectly normal and to be expected.

However, just because it's expected doesn't imply it's safe. Because an RV has many appliances plugged into AC power, these leakage currents will add together. So you can create a dangerout fault current that's sufficient to put your heart into ventricular fibrillation that's deadly. Secondly, an unbonded RV (that's the actual term rather than ungrounded) could have an internal medium current (hot water heater element) or high current (compromised insulation on a wire that's rubbing on a metal frame, for example), which will create a high fault current that's likely to be instantly fatal if you touch any part of your RV while standing on the wet ground.

In short, if you plug your RV into an ungrouded outlet, you will never be safe. And a ground rod is not a substitute for a ground wire (Equipment Grounding Conductor) that's properly bonded back to the incoming service panel's Neutral-Ground bonding point. And as noted in my video, one of the quickest ways to determine if you have a stray voltage is by using a Non Contact Voltage Tester. More on this later, but do you have any more questions at this point?

Mike Sokol
mike@noshockzone.org
www.RVtravel.com
www.RVelectricity.com
www.NoShockZone.org

 

[Old Crow]

Thanks, Mike. Very interesting discussion.

I do have a question. Some of us have truck campers which we bought as minimally-equipped 'shell' models and those don't have 120-volt inlets, AC distribution panels, circuit breakers, etc. But we do occasionally need 120-volt power in the camper, typically to run a portable battery charger or 120-volt electric heater (and I'm sure some members also run microwaves, toaster ovens, phone chargers, TVs, etc that way).

Our campers have tie-down doors so we run a heavy-duty extension cord from the shorepower outlet (typically a campground pedestal or home/garage outlet) through the tie-down door to the appliance.

Do you have any electrical safety concerns or best practices for running a shorepower extension cord into our campers in this manner?

.

 

[jmsokol]

Thanks, Mike. Very interesting discussion.
Do you have any electrical safety concerns or best practices for running a shorepower extension cord into our campers in this manner?
.

I've thought about this a lot as it applies to code, and have a few ideas on the safe way to do it. According to all my own studies and experiments, anything metallic that has an AC power cord run inside of it or over it needs to be "bonded" (grounded) to the "EGC" (Equipment Grounding Conductor) commonly called the ground wire. Note that this is NOT a ground rod stuck in the dirt. The only thing that works to actually "ground" your vehicle is a direct connection to the incoming service panel's Neutral-Ground bonding point. And that means connecting (bonding) the green/ground wire of your extension cord to the frame of your RV or truck. Here's why. Consider the scenario where the extension cord powering your camper is draped over a sharp piece of metal or pinched in a door. If that sharp piece of metal breaks through the insulation, then 120-volt/hot wire can contact the chassis, energizing it with 120-volts. If you have a proper "ground" connection on your vehicle, then this short circuit will trip the circuit breaker feeding the camper. GFCI protection is another thing that helps keep this kind of hookup safe, but don't bet your life on a GFCI.

I've not seen a commercial product like this, but it could be as simple as a short male-female extension cord with a jumper from the ground pin of the power cord to the chassis of the truck. I'll look around for something simple to install.

 

[jmsokol]

One other thing to note is that reversed polarity by itself won't cause a hot-skin/stray-voltage condition. More on this later....

 

[larryqp]

Many years ago we traveled in Mexico, both on the west coast of the mainland and the Baja. Most campgrounds had terrible electricity. Often they had very high or very low voltage, open ground, reverse polarity. I made it a habit to use a simple plug in tester and voltmeter before plugging in. Sometimes one campsite would be okay and another would not be okay, and we could get them to put us in the okay site. At most campgrounds we just didn't plug in at all and ran off batteries and solar power as if we were boon docking. If the electricity was okay after testing and we did plug in I used a surge protector plugged into the electric pedestal then plugged my camper into the surge protector. The surge protectors aren't cheap, but usually much cheaper than the damage a surge can cause.

Another thing we did was bring a drop light with us. At night we could plug that into the pedestal directly to light up our campsite, without using our camper light and running down the battery. I figured if the drop light fried it was cheap enough to replace.

 

[Helmut]

Thank's to all of you. I'm still here, working my way through all that info esp. Mike's. Fact is, we are travelling south and i am quite sure my "normal" electricity source will have no ground. My solar ( 400 watt, 150 amp / 12 V ) won't get me enough to keep my batteries fully charged ( shorter daylight time / cloudy / heat ) - so i am looking for a way to work around this. FWC told me there must be a short somewhere in my 110V system. If that is right there are only the fridge, converter/inverter or those two build in power outlets. According to Mike ( and if i understand him correct ) my observation is to be expected as soon as i plug in without correct ground wiring. I will try to post some pics of " typical mexican " hookup and my measurements after unhooking the 110V appliances mentioned above. Internet is not always available so my responding can take some time.

 

[jmsokol]

The key to understanding how you can develop a hot-skin/stray-voltage is to realize that hot-skin voltage comes in several versions, what I call low-current, medium-current and high-current. Any of these can develop whenever you have an open "ground" connection (actually call the EGC or Equipment Grounding Conductor) that's bonded to the incoming service panel's G-N bonding point. Note that a putting in your own ground rod doesn't actually "ground" your RV.

A low-current hot-skin is caused by normal leakages inside of your RV appliances, and typically is just a few mA (milli-amperes) up to maybe 20 or 30 mA, depending on appliance leakage. And it typically results in around 50 to 60 volts (1/2 the line voltage). If it's on the low side of a few mA, then you might just feel a tingle if you stand on the wet ground and touch your RV. If it's 20 to 30 mA (from combined leakages that could still be within UL limits), then you would feel a really big shock, possibly so much that you can't let go of anything you touched while standing on wet ground. And 30 mA is the lower limit of sending your heart into fibrillation, which can be deadly with just a few seconds of contact. This is the only type of fault that would have its voltage lowered by your own ground rod with perhaps 25 ohms impedance.

Medium-Current hot-skin voltage is typically a few amperes or two, and many times caused by a water-heater element that's lost its hermetic seal from overheating. This usually results in 120-volts hot-skin, and is easily deadly if you're standing on wet ground and touch anything metal on your RV. Note that this is NOT a short, just a medium impedance shunt to chassis. This 2 or 3 amperes of current going into the water isn't enough to trip a circuit breaker, but it would overwhelm any ground rod.

High-Current hot-skin voltage is the result of a short-circuit from a hot wire to the RV chassis, typically when the insulation of a wire rubs through and makes direct contact with the chassis, or perhaps a screw is driven though a wire inside of a wall (oops). This can provide up to 30 or 50 amperes of fault current and should instantly trip any circuit breaker. Again, this is the only fault condition that's actually a short circuit.

Let me know if this makes sense. I've been doing this for over 40 years, so I have a lot of background with this sort of failure.

 

[Vic Harder]

Thanks for sharing your knowledge and experience Mike! I am confused on a couple of points.

1. Regarding the need to have a separate ground wire installed when plugging in an extension cord. If the camper is wired correctly (assuming factory FWC and ATC are) then the ground wire in the camper is already going to the camper frame, and that is grounded to the truck frame via the factory installed wiring joining the truck and camper. So why would I need to install a separate ground wire?
2. I get that a simple spike into the ground close to my camper is not a good ground. If the dirt is dry, it may not be a ground at all. Given that the the OP was asking about situations where there just is no EGC installed (open ground/two wire circuits in Mexico), is there a way to plug in AND be safe?

 

[jmsokol]

Thanks for sharing your knowledge and experience Mike! I am confused on a couple of points.

1. Regarding the need to have a separate ground wire installed when plugging in an extension cord. If the camper is wired correctly (assuming factory FWC and ATC are) then the ground wire in the camper is already going to the camper frame, and that is grounded to the truck frame via the factory installed wiring joining the truck and camper. So why would I need to install a separate ground wire?
2. I get that a simple spike into the ground close to my camper is not a good ground. If the dirt is dry, it may not be a ground at all. Given that the the OP was asking about situations where there just is no EGC installed (open ground/two wire circuits in Mexico), is there a way to plug in AND be safe?

If you're referring to the bond between the truck and the camper shell, then indeed you don't need a second ground/bond connection. However, if you simply run an extension cord into a camper that doesn't have a factory installed shore power connection, then you have to establish at least one EGC (the green ground wire in an extension cord) bond to the chassis. So it could be bonded to either the truck chassis or the camper chassis. Is that what you're referring to?

If I were connecting to pedestal power without a proper "ground" connection, then I would use an extension cored with a built-in GFCI breaker. That way if you were to get shocked between the camper or truck chassis and earth, the GFCI should trip and protect you from electrocution. Can you get away with a 20-amp power connection? If so, those are readily available in the contractor section of any big box store such as Lowe's or Home Depot.

 

[Vic Harder]

If you're referring to the bond between the truck and the camper shell, then indeed you don't need a second ground/bond connection. However, if you simply run an extension cord into a camper that doesn't have a factory installed shore power connection, then you have to establish at least one EGC (the green ground wire in an extension cord) bond to the chassis. So it could be bonded to either the truck chassis or the camper chassis. Is that what you're referring to?

If I were connecting to pedestal power without a proper "ground" connection, then I would use an extension cored with a built-in GFCI breaker. That way if you were to get shocked between the camper or truck chassis and earth, the GFCI should trip and protect you from electrocution. Can you get away with a 20-amp power connection? If so, those are readily available in the contractor section of any big box store such as Lowe's or Home Depot.

Doh. Yeah, if using an extension cord to go directly to an appliance (electric heater comes to mind) then that appliance could not be grounded. However, I think the OP is using the extension cord like more RV'rs do in a campground, and plugging it into the shore power connection on the camper. Hence it would be bonded to the truck/camper.... problem the OP mentioned is that there is NO ground on the pedestal.

So, GFCI dongle like this one would do the trick?
https://www.amazon.com/dp/B00TQOF3FI?aaxitk=GmQDp1XRWlKbw3IF09idcA&pd_rd_i=B00TQOF3FI&pf_rd_m=ATVPDKIKX0DER&pf_rd_p=3ff6092e-8451-438b-8278-7e94064b4d42&pf_rd_s=desktop-sx-top-slot&pf_rd_t=301&pf_rd_i=rv+gfci&hsa_cr_id=3318346080901&sb-ci-n=productDescription&sb-ci-v=Tower%20Manufacturing%2030438024%20Auto-Reset%2015%20AMP%20Inline%20GFCI%20Triple%20Tap%20Cord%2C%202%20Feet%2C%20Yellow&sb-ci-a=B00TQOF3FI

 

[jmsokol]

So, GFCI dongle like this one would do the trick?
https://www.amazon.com/dp/B00TQOF3FI?aaxitk=GmQDp1XRWlKbw3IF09idcA&pd_rd_i=B00TQOF3FI&pf_rd_m=ATVPDKIKX0DER&pf_rd_p=3ff6092e-8451-438b-8278-7e94064b4d42&pf_rd_s=desktop-sx-top-slot&pf_rd_t=301&pf_rd_i=rv+gfci&hsa_cr_id=3318346080901&sb-ci-n=productDescription&sb-ci-v=Tower%20Manufacturing%2030438024%20Auto-Reset%2015%20AMP%20Inline%20GFCI%20Triple%20Tap%20Cord%2C%202%20Feet%2C%20Yellow&sb-ci-a=B00TQOF3FI

Yes, that should protect you from getting shocked or electrocuted between the frame of the truck/camper and the earth. Interestingly, even though this is called a 15-amp plug, it's built with 12-gauge wire. That means it is actually rated for a 20-amp circuit breaker on the pedestal or home outlet because there's no difference in contact current carrying ability for 15 or 20 amp plugs and outlets. Both outlet styles will carry 20-amps of current. It's the gauge of the wire that limits them to 15 amps (14 gauge wire) or 20 amps (12 gauge wire).