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  • 911? Voltage on my propane straps

    Lesson learned here… if you use an extension cord to keep your battery charged. Make sure there’s a ground prong.
    Last edited by NCW_Wander; 03-25-2022, 04:39 PM.
    Phil & Jenn | North Central WA
    2022 Reflection, 31MB (Pkg's: Power, Arctic, 2nd AC, Solar)
    2021 F350 Tremor, 6.7L Diesel, SRW

  • #2
    Hi Phil,

    The ground pin on the shorepower cord is a safety . . . there should not be current flowing back to the source through this wire as a "normal" thing. Google "RV Hot Skin" for more information on the situation that you have. There should be no way for there to be electrical potential between the frame of the RV (the propane straps) and the ground you are standing on.

    Rob
    Cate & Rob
    (with Border Collies Molly & Angel + Kitties Hazel & Elsie)
    2015 Reflection 303RLS
    2022 F350 Diesel CC SB SRW Lariat
    Bayham, Ontario, Canada

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    • #3
      Originally posted by Cate&Rob View Post
      Hi Phil,

      The ground pin on the shorepower cord is a safety . . . there should not be current flowing back to the source through this wire as a "normal" thing. Google "RV Hot Skin" for more information on the situation that you have. There should be no way for there to be electrical potential between the frame of the RV (the propane straps) and the ground you are standing on.

      Rob
      There can if the extension cord is long enough. There is nearly always stray current in the soil from leaks from utilities and damaged equipment. This can cause voltage gradients in the soil where the voltage of the soil can be significantly different from the EGC which is in contact with the soil at another location.

      John & Kathy
      2014 Reflection 303RLS
      2014 F250 SC SB 6.2

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      • #4
        Jkwilson -- started searching the 'net for more information and fell down a DEEP rabbit hole labeled "NEV" (Neutral-to-Earth Voltage). Watched a video by Mike Holt that made my head hurt.

        For the OP, NCW_Wander -- I strongly suggest doing a Hot Skin test on your trailer. If it fails you'll want to sound "Red Alert" and go to battlestations. (Yes, I'm tired.) In other words, get it taken care of ASAP.

        Mike Sokol has several videos and online articles about the hazard. Below is one of them.

        Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

        2017 Ford F-350 DRW, '19 315RLTSPlus

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        • #5
          How do you know there is voltage present at the straps?

          Verify that the extension cord is not the problem. Plug an outlet tester into the extension cord or measure voltages leg to leg and leg to ground.

          The Sokol hot skin information is a good source.
          Ted
          2021 Reflection 310RLS
          2020 F350 PS,CC,LB,SRW

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          • #6
            Jkwilson

            If there was a voltage difference between the earth at the trailer and the ground rod at the source, wouldn’t the ground wire in the extension cord complete the circuit back to the source? Thus, feet on the earth and hand on the RV chassis would complete this circuit. Without a ground wire connection in the extension cord would break this theoretical connection.

            I would suspect that there is a relatively high resistance contact between a line voltage wire and the RV chassis. Not enough current to pop the breaker. With a ground wire connection back to the panel, this voltage follows this low resistance path back to the source. Without this wire, the voltage is looking for another path . . . potentially through a person with a hand on the RV and feet on the ground.

            This is a dangerous situation that should be sorted out following the “RV Hot Skin” diagnostics.

            Rob
            Cate & Rob
            (with Border Collies Molly & Angel + Kitties Hazel & Elsie)
            2015 Reflection 303RLS
            2022 F350 Diesel CC SB SRW Lariat
            Bayham, Ontario, Canada

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            • #7
              Originally posted by Cate&Rob View Post
              Jkwilson

              If there was a voltage difference between the earth at the trailer and the ground rod at the source, wouldn’t the ground wire in the extension cord complete the circuit back to the source? Thus, feet on the earth and hand on the RV chassis would complete this circuit. Without a ground wire connection in the extension cord would break this theoretical connection.

              I would suspect that there is a relatively high resistance contact between a line voltage wire and the RV chassis. Not enough current to pop the breaker. With a ground wire connection back to the panel, this voltage follows this low resistance path back to the source. Without this wire, the voltage is looking for another path . . . potentially through a person with a hand on the RV and feet on the ground.

              This is a dangerous situation that should be sorted out following the “RV Hot Skin” diagnostics.

              Rob
              Only if the jacks are making good contact with the soil.

              If the ground wire connection to the frame is good, you aren’t going to get a voltage on the RV regardless of what happens with the hot wire. Virtually every time you see this situation, it’s a missing ground in the extension cord, a mis-wired outlet, an improperly grounded subpanel or excess distance from the panel ground. Stray voltage is a constant problem in livestock operations and pools. The common way to check is to stick a rod in the ground and measure from it to the ground pin on an extension cord. I’ve seen as much as 31VAC, and I have 4.5V in the soil 35ft from the properly grounded sub-panel on my barn.

              John & Kathy
              2014 Reflection 303RLS
              2014 F250 SC SB 6.2

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              • #8
                The ground connection on an extension cord is a safety device and should not be considered a primary return for a properly wired system. All AC voltage is designed to go from the hot leg to the neutral. Any break in this is BAD. Think back many many many years. Outlets were only 2 prong. Then came grounded and double insulated. Double insulated is primary insulation of the device by non conductive means followed by a conductive barrier connected to the ground to provide an emergency return path for stray voltage.

                Simple test, possibly using a 30A to 15A adapter try a different power outlet, maybe even ask a neighbor to use their power to perform the simple test (10-15 minutes) and remember to be nice with the camper full charged.

                I would suspect that the OP will find a broken ground or a mis wired circuit. I would start by ohm testing the extension cord being used, then verify that all of the connections in the Unit are correct and making contact by ohming the chord to the panel. Once those are verified, then work back to the outlet being used to power the unit. While in the breaker panel (everything unplugged and off, battery and solar disconnected) I would inspect the power wire to terminal connections for proper connection (just because you get an ohm reading does not mean it can carry the load) and ensure that the insulation is properly stripped and not inhibiting the connection. Where possible verification of the connector on the outside of the camper to the cable running to the panel also. One other thing (been bit by this personally) verify that any adapters being used are making proper connection at the unit (I.E. the camco doggone adapter to relieve the stress on the cable something like this https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1).
                Joseph
                Tow
                Vehicle: 2024 GMC K3500 Denali Ultimate Diesel
                Coach: 303RLS Delivered March 5, 2021
                South of Houston Texas

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                • #9
                  Not a fan of that Camco 90 deg adapter. The connection is clocked at such an angle that the weight of the power cord tends to rotate the adapter to a loose connection position.
                  Ted
                  2021 Reflection 310RLS
                  2020 F350 PS,CC,LB,SRW

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                  • #10
                    Please correct me if I am wrong here. Way back I had a hot skin issues with my Wilderness. It came with the 30A cord hard wired. I used an adapter that the ground pin was missing, and a 2 prong extension cord. I got bit touching the trailer in wet conditions. I then flipped the 2 prong plug over and everything was fine after a neighbor mentioned to try that. I know the new 2 prong cords have one blade wider than the other so the can only go in one way, but older ones don't.

                    Without the ground wire a 2 pron cord/plug just has the hot and neutral. Correctly plugged in hot-hot neutral to neutral everything should be good, but if reversed you have the hot going to the neutral. Could that be what happened here?

                    Just curious
                    Keith
                    2018 Reflection 150 Series 220RK 5th whee, Star White 2022 F350 King Ranch CC Long bed (HAL) (CCC 4062lbs), B&W 25K OEM Companion,. SteadyFast system, Trailer reverse lights, rear receiver spare tire holder, storage tube, sumo springs, Victron MultiPlus 12/120/3000, Solar, Custom 6K axles upgrade, and other modifications.

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                    • #11
                      How are you measuring and what made you measure the propane straps?
                      2018 Dodge 3500 6.7 Cummins w Aisin and 9 cup holders
                      Not to brag or anything about my finances, but my bank calls me about every day to tell me my balance is OUTSTANDING!

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                      • #12
                        Having a source of AC power without the third prong (safety) ground is a situation that most owners would never encounter. What this has proven in the originally described situation is that voltage is "leaking" to the safety ground circuit (connected to the chassis of the trailer) and returning to the source by this route rather than through the neutral wire. A GFCI protected circuit would have opened in this situation, but a high resistance connection would not be enough to open a normal circuit breaker.

                        With the trailer sitting on rubber tires and likely wood or plastic blocks under the landing gear, this stray current is looking for a path back to the source. Through the earth is a possibility if a connection is made between the owners feet on the earth and his hand on the propane strap screwed to the trailer frame.

                        While the third wire in the cord will take care of this stray current, it is still not right that voltage is leaking to this safety ground circuit and chassis within the RV.

                        My background in this is from boating . . . where swimming back to a boat plugged into shorepower (or with the generator running) can be deadly in a similar situation.

                        Rob
                        Cate & Rob
                        (with Border Collies Molly & Angel + Kitties Hazel & Elsie)
                        2015 Reflection 303RLS
                        2022 F350 Diesel CC SB SRW Lariat
                        Bayham, Ontario, Canada

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                        • #13
                          Interesting discussion here. I deleted my original post because I was embarrassed. I’ve worked for electric utilities more than a decade and honestly should’ve known better. Here’s some more detail for clarification though.

                          FW was parked in the driveway, on asphalt. My levelers had those square orange plastic thingies between the asphalt and the jacks (not sure it would’ve made a difference otherwise. Asphalt’s more of an insulator.). The weather was nice, so I was barefoot, and because of the angle of the trailer, I was standing in the lawn. Normally I wear boots with dielectric soles. We were getting ready to leave that afternoon for my daughters VB tournament a couple of hours away. I had gotten the propane tanks filled and was strapping them in when I felt it. At first I thought it was just a rough edge on the steel strap, until I took a closer look at the smooth edge. I happened to have an 4’ ground rod in my shop, so I drove that into the lawn, put my boots on, grabbed my multi-meter, and tested the strap. I didn’t know if it was AC or DC, so I tested both. Got 16V to ground on the DC setting and 50V to ground on AC. As I started down the list of “potential” problems (pun intended), I unplugged the trailer. That solved it, so I knew it was on the AC side. I don’t know what happened… I suspect my 3 month old pointer mistook one of my extension cords for a chew toy while I was working in the shop last week. But I should’ve noticed that there wasn’t a ground prong on the extension cord that I used to connect the trailer (I also should’ve noticed the chew marks). And that’s really embarrassing. An open-ground seemed like a pretty reasonable explanation. I’d never heard of Hot Skin, but I know what stray voltage is. I replaced the extension cord, plugged the trailer back in and tested it again. I got 0.5V to ground AC.

                          I know stray voltage from a totally different aspect, and so I too went down a very quick rabbit hole. I happen to have one of those proximity potential-testers that you use for outlets. So, the first thing I did when we arrived last night, after connecting to the 50A pedestal, was test the frame with the proximity tester. It checked out. So, despite the embarrassment, I learned a useful lesson that’ll keep my family safe going forward.
                          Phil & Jenn | North Central WA
                          2022 Reflection, 31MB (Pkg's: Power, Arctic, 2nd AC, Solar)
                          2021 F350 Tremor, 6.7L Diesel, SRW

                          Comment


                          • #14
                            I would suspect the problem cause still exits that somewhere on the trailer the frame is connected to a voltage potential. The repaired cord ground connection is masking it by putting the frame at ground wire potential. It would be good to check for a leak to frame on the trailer by measuring line to ground resistances. The resistances should all be infinite, ie no connection. Just to be safe.
                            Ted
                            2021 Reflection 310RLS
                            2020 F350 PS,CC,LB,SRW

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                            • #15
                              NCW_Wander

                              "Embarrassment", not fun to say but it is surely the way most of us learn lessons, whether we do it ourselves or someone does it for us. Plenty here have done it so don't feel bad, you have helped me for sure and probably others to be a little more diligent in what we do as far as electrical connections and "feelings" of things that may not be right.

                              Thanks for the post,

                              Brian
                              Brian & Michelle
                              2018 Reflection 29RS
                              2022 Chevy 3500HD

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