Trailer frame electrified?

[Timon]

This sounds like a grounding problem with the campground ground in the section you're in since the older area reads 0 plus other coaches show the same 7V offset.

This has the potential to be a serious issue. I'd tell the manager about the issue and have them bring a electrican out and do some checks because someplace there is a grounding problem.

[wbarnes]

Hi JMooney,

Yes, I would describe the sensation as a weak 9v battery on the tongue. I am just not sure if that 6-7 volts and that tingling sensation from frame are normal or not. And it is only felt if hands are wet (at least thus far).

I checked the "Reverse Polarity" fuses in the fuse box under fridge. They are good. I also checked the 30amp inline fuse at battery and it is also good. When I go back out to camper this week I will "clean up" the ground wire from battery and ensure it has positive connection.

Will keep you all posted on what I discover.

[wbarnes]

Timon,

This seems to be the common concensus from what I have been reading (that it more likely to be CG ground problem). I am using the same thinking as you; that if others in my immediate area show same voltage and those in another section are not; it must be a campground problem. But what I can't explain against that theory is why is the receptacle (when tested) showing clean.

Bill

[VicS1950]

Originally Posted by wbarnes

...
Is the frame to copper pipe a valid test and what is the expected voltage range for this specific type test (if valid)?


Bill

As has been said already, there shouldn't be a 7 volt potential difference in the ground system.

That said, a copper pipe in the ground is not necessarily giving a valid test. Ground conduction of a copper pipe includes many things such as surface area, moisture, soil type, and some I'm forgetting. Back in the day a 1/2" diameter copper clad or galvanized ground rod was considered sufficient. Now a matrix of 3 driven ground rods is considered the better option for grounding.

What that means is that the potential difference of 7 volts could actually be much higher if your ground rod had better conduction. As an experiment you could pour some salt water solution on your ground rod area to see if the test voltage increases.

I'm not going to guess what the problems are. I recommend informing the CG owner and requesting another site. Once there duplicate your tests to make certain the problem is not with your RV.

vic

[edatlanta]

The campground where I am hosting right now had a problem with several campers in one area with complaints of getting shocked (or tingled) when touching outside metal parts of their rigs. The campground called in an outside electrician and he traced the problem back to one older rig. When it was plugged in to the pedestal the problem existed for all others on that same circuit. He was told not to plug in until his problem was solved. This was just yesterday so I haven't heard what his internal problem was. The campground circuit was checked completely at each pedestal and found not to be the problem.

[Jmooney]

The reason that the 110V ground and neutral are not bonded together in an RV is because the RV frame has no reference to earth ground. It is considered a floating ground (even with leveling feet down it is not considered grounded)


This is important because if the polarity on the camp ground post was reversed, then "hot" would be entering the RV on the White neutral wire, and, if it were bonded to the ground wire ( which is also grounded to your RV frame), the 110v Hot side would be in contact with your trailer frame.


If you were standing on a wet surface and touched the RV frame - you would conduct 110V to earth ground. Ouch!


Now back to the OP - this all still sounds very suspicious of an issue with Positive side voltage in contact with your trailer frame and/or ground wire.


The other trailers having the same reference to voltage is making us all think that this is an issue with CG power.


I'm not sure you are going to get your answer here until you figure out:


1) Why your battery is not charging - is that problem somehow related to what's going on or was it caused by some greater issue
2) Do you still have this voltage reference to your frame when connected to some other AC power source (at Home or on a gen set)


Please be very careful with your testing - 50amps can be quite deadly.

[jmsokol]

I'm Mike Sokol from the No~Shock~Zone. Thanks for posting a link to my blog about RV Electrical Safety here. There's definitely something fishy about the voltage you're measuring between your RV chassis and earth ground. In fact, there's a mis-wiring condition I call a Reflected Hot Skin Condition that will allow a ground fault from one campground pedestal to be reflected to multiple pedestals on the same daisy chain loop. I've written a basic paper about this somewhere and will see if I can find it and post a link tomorrow. The really dangerous thing about this mis-wiring condition is that it can change from a tingle to full electrocution at any time. So it really needs to be checked out and corrected by the campground electrician immediately.

[jmsokol]

I've talked to a few of my EE buddies about this situation, and we all agree that if you're seeing this same voltage at multiple RVs plugged into different pedestal outlets, then the likeliest cause is a compromised Ground-Neutral bond in the campground's service panel leg that's feeding all those pedestals. This can be very dangerous since a ground fault in a single RV can be reflected to everyone else on the campground loop. Also be aware that because UL won't allow the EGC ground to be disconnected by any safety device, that even a Progressive Industries EMS can't disconnect you from a reflected hot ground (but it will shut down your interior power), nor will any GFCI trip and protect you no matter where it's located in the circuit.

The best way for the campground to test for a proper impedance EGC ground is to use a ground loop impedance tester such as a SureTest Analyzer or Amprobe INPS-3. These are a little expensive for a casual user since they cost around $300, but certainly any campground or electrician should be able to afford one. I'm advocating that all campgrounds are checked for ground loop impedance every few years, or anytime a pedestal has be damaged and repaired or replaced. But its slow going because of the "it's never happened to me" crowd. However, I get emails about this all the time and have mocked up a demonstration to prove how this works and ways to measure it.

Mike Sokol
No~Shock~Zone

[Plowtoy]

So Ive read through all of this. One of the statements was to clean the connections at the frame. I asked a similar question when I bought our latest camper last spring. Thought I had it figured out (found the plug at the house was not correct. Its an older home, but ground is not working at that plug. I switched plugs to one with a working ground and seemed better), but still am feeling an ocasional tingle (only from the frame, not the aluminum skin as far as I can tell) if I make contact with the sissor jacks up (has not been noticable when down). Looking farther into it, the bare copper wires (I think there are 2 or 3) that come through the floor to the frame right where the breaker box is, is all rusted and crappy looking. Is it possible that the connection is just bad and will cleaning it help? Looking to get it out this weekend and work on it, unplugged of corse... Thinking it may be worth my while to clean all grounding connections under the camper. Im not overly excited about bringing my 6mo out until I can get this taken care of.

[wbarnes]

Hi folks

I did so more testing today with one of the campground workers and we made an interesting observation but we are not able to rationalize what it means.

The campground circuit I am on has 7 campers. While each receptacle has its own hot wire, they share the same neutral. The campground worker believes the ground is bonded to neutral (bootleg ground).

We tested all the campers that are on this panel for their frame to ground voltage reading. All were about 5.4 volts. We tested the pedestal outlets and they show clean. Now the interesting observation......the receptacles are housed in a grey cabinet on the wooden pedastal. We tested the from one of the cabinet screws to the ground and it had 5.4 volts (despite its receptacle showing ground-to-neutral as 0 volts). We tested from the screw to ground with all the campers unplugged and plugged in....same 5.4 volts.

Thoughts?

Bill


Ok, now the interesting observation. W

[jmsokol]

Originally Posted by wbarnes

Hi folks

I did so more testing today with one of the campground workers and we made an interesting observation but we are not able to rationalize what it means.

The campground circuit I am on has 7 campers. While each receptacle has its own hot wire, they share the same neutral. The campground worker believes the ground is bonded to neutral (bootleg ground).

We tested all the campers that are on this panel for their frame to ground voltage reading. All were about 5.4 volts. We tested the pedestal outlets and they show clean. Now the interesting observation......the receptacles are housed in a grey cabinet on the wooden pedastal. We tested the from one of the cabinet screws to the ground and it had 5.4 volts (despite its receptacle showing ground-to-neutral as 0 volts). We tested from the screw to ground with all the campers unplugged and plugged in....same 5.4 volts.

Thoughts?

Bill


Ok, now the interesting observation. W

If indeed they've wired the pedestals with bootleg grounds, then this is an easy answer. When there's a voltage drop on a hot wire due to a current draw, there's an equal and opposite voltage drop on the neutral wire (but 180 degrees out of phase). So a branch circuit that's dropped from 120 to 110 volts can have 5 volts drop on the hot wire and 5 volts drop on the neutral. That's normal, but isn't supposed to influence the ground wire. However, if the ground an neutral are bonded together in each pedestal (a code violation), then the ground bus in the outlet will biased to the same potential as the neutral voltage drop. That will show up as a variable voltage between the ground wire and an earth connection. I've seen this many times in the pro-sound industry (my main gig) and only occasionally in a campground. But sounds like that's what's going on. Please PM me directly with the campground details since what they're doing is not only a serious code violation, it's very dangers and could become a shock hazard very easily.

Mike Sokol
mike@noshockzone.org

[jmsokol]

Originally Posted by wbarnes

We tested the from one of the cabinet screws to the ground and it had 5.4 volts (despite its receptacle showing ground-to-neutral as 0 volts). We tested from the screw to ground with all the campers unplugged and plugged in....same 5.4 volts.

One of the ways I test for bootleg grounds is to carefully measure the voltage between the neutral and ground contacts on an outlet while there's a sufficient load on that branch circuit to cause a significant voltage drop. Under no load there should be very close to 0 volts between Ground and Neutral. However, if you load the pedestal enough that the Hot to Neutral voltage drops from 120 volts down to 110 volts (pretty common in a campground), you should then measure between 2 to 5 volts between the Ground and Neutral. That proves that that the Neutral and Ground are not "Bootlegged" together and are indeed separate wires back to the service panel. It's perfectly normal and expected to measure around 1 volt or so between the Ground and Neutral contacts in any building or campground with electrical activity.

As I noted on my previous post you can get a $300 Ground Loop Impedance Tester that will warn you that there's not enough predicted impedance in the EGC ground wire and likely a bootleg ground.

So if under no load you're still measuring around 5 volts between your local EGC Ground (the pedestal enclosure) and the earth ground (a rod driven into the dirt), then that indicates there a bootleg ground somewhere upstream of the pedestal you're plugged into, perhaps at a subpanel or even at one of the other pedestals in your group. I'll note that you can get similar (but not exactly the same) load/no-load G-N-E voltage readings with a swapped Ground and Neutral in a receptacle/outlet. Hard to believe, but swapped Grounds and Neutrals are fairly common in residential and office wiring.

This is fairly high-level troubleshooting that few electricians will understand, which is why bootleg grounds are hard to find. If fact I spend a fair amount of my business troubleshooting why the power wiring is making sound system hum and buzz. That voltage on the ground wire is what causes something we call ground loop hum.

Mike Sokol
No~Shock~Zone

[Jmooney]

Bill - did you ever identify when your battery was dead?

[clubhouse]

I have nothing contrustive to add. Just wanted to thank all of you for this discussion, I feel a bit smarter for reading, and re-reading, the posts.

[Jmooney]

Yea, I Had to re-read Mikes technical description a few times as well.

[norty1]

Yes, it's like reading the articles in a Playboy. The pictures seem to make things clearer! LOL

[Jmooney]

There are articles in playboy?

[jmsokol]

Originally Posted by Jmooney

Yea, I Had to re-read Mikes technical description a few times as well.

I know it seems mind boggling, but even complex electrical circuits are just a bunch of simple circuits connected together, just like a steam locomotive is a bunch of simple levers and pistons that perform a complex function. In addition to studying Electrical Engineering in college, I also liked to set up my own experiments that showed basic electrical principals like voltage drop due to current flow, etc... While you can do this all with equations and schematics (and I often do), it's really enlightening to design a demonstration you can have right in front of you on a table.

The problem with electrical distro circuits is that not a lot of people want to play with this stuff, and probably shouldn't be messing around with live 120-volt circuits anyways. However, since I'm trained in electrical safety and often work on live circuits for pro-audio distribution, I can do these experiments with minimal danger to myself. So kids, don't try this at home.

If you're curious, here's one of my portable No~Shock~Zone demonstrations that allows me to hot-skin electrify the chassis of pro-sound gear as well as create and mitigate ground loop hum at will. Mike Sokol: Electrical Shock Prevention in Sound Systems - B&K Precision I also have a No~Shock~Zone seminar designed for RV power safety where I hot-skin energize an RV to various voltage to show how it can be detected and corrected. Let me know if you think that Jayco would like me to do a NSZ demonstration at a Jayco camp meeting on the east coast.

[wbarnes]

Hi Mike et al,

I am heading out to the campground tonight and will post more details once I have an update. They had scheduled a "bonafide" electrician today to investigate; but I have not yet had an update.

Mike, you made a comment that has made me go "hmmmm". You mentioned about a ground loop hum. Coincidentally; last weekend; we had a loud audible hum coming from the TV set speakers that was drowning out the audio of the movie coming out of the surround sound RV speakers. I haven't had chance to assess the "why" but noted that if the Composite L/R cables from the stereo system are pulled out, the hum stops. Now I am wondering if anything to do with the issue I have on the HotSkin.

Bill

[wbarnes]

The campground had the electrician come in Friday. Although I didn't speak with them directly, I am told that it is acknowledged that something is not right; they just don't know what exactly is causing it.

I have shared Mike's articles and this discussion thread with them in hopes that it may help point to the issue.

I redid some tests (RV Frame to Ground, Pedastel box screw to ground) and they are now showing 12 volts; up from the previous 5-7 volts. This would seem consistent and expected based on the Mike's last post indicating that as voltage drop occurs on the hot; an equal increase occurs on the neutral. Assuming bootleg ground (as was indicated by the installer); then I would expect this voltage increase to show on the RV frame.

Hoping this week brings more investigation and resolution.

Bill