Voltage in the frame?

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lhemrick

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2011 30' Salem Cruise Lite. I was jacking the trailer to change a tire. My ear touched a bolt and it tingled. Got a meter and it has 24 volts on the frame. What is causing that?
 

Kirk

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Got a meter and it has 24 volts on the frame. What is causing that?
I assume that you measured between the RV and earth ground and alternating current voltage and that the RV was connected to shore power?

You have what is called "hot skin" condition. There are several things that could cause that and the first it to check that your polarity of the power to the RV is proper and that your RV's power plug has a good ground pin that is connected to the RV chassis with nearly 0 ohms.

RVelectricity – What is Hot-Skin/Stray-Voltage?

 

DonTom

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2011 30' Salem Cruise Lite. I was jacking the trailer to change a tire. My ear touched a bolt and it tingled. Got a meter and it has 24 volts on the frame. What is causing that?
Test that again with a CHEAP ANAOLOG voltmeter. I bet you were using a digital voltmeter.

-Don- Reno, NV
 

Mark_K5LXP

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It's standard practice to use a "burden resistor" of 1K ohm between the two test points and measure the voltage with a high impedance meter (DMM) across that, eliminating the variable of the voltmeter input impedance. Ohm's law will determine the leakage current and from there one can discern if the leakage current is excessive or not based on the standard one wishes to observe. There is an NFPA standard for RV's but I don't have a copy, so not sure what the exact RV test would be. One reference I saw mentioned 3.5mA maximum for a grounding conductor path. That would be 3.5V across the 1K resistor. One can also use a contactless voltage detector to measure for "hot skin" conditions. I would say if there's enough there to get a "tickle" on bare skin then I would want to know where it's coming from.

Mark B.
Albuquerque, NM
 

Isaac-1

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I agree you have a hot skin condition, there are a number of potential causes, one is a wire where the insulation has been nicked by a screw or sharp metal edge that is letting voltage leak to the metal skin/frame. Locating the cause can be a challenge, start by turning off the breakers one by one, and checking to see if/when the voltage goes away, that will tell you which circuit the leak is on. You will then need to find the leak which may be in the wiring, in an appliance on the circuit, etc. If none of the breakers make it go away then the problem may be in your shore power wiring, etc.
 

John From Detroit

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If you have an open ground the theory is there will be up to 60 volts on the SKIN (30 amp rig) bit more complex math for a 50 amp rig.
The explanation is that Romex makes one fantastic capacitive voltage divider... Just not a lot of current. (Which is why a cheap meter will give different readings from a quality meter).
Another option is the distance from you to the electrical system ground.. in some cases the "Voltage" is in the ground but math wise I really don't want to go there. (it can be rather complex) This is not as common as it once was however.
 

CharlesinGA

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Heating elements of the fridge and water heater are both very good suspects. Plug into a ground fault receptacle. Does it trip it? This makes finding it easier. Start with unplugging the fridge cord on the backside of the fridge, flip off the water heater if you had it on. Process of elimination, just one item at a time. Make sure whatever you are checking is actually functioning at the time.

Charles
 

8Muddypaws

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I had that problem too. I discovered that the plug I had used from my garage had the hot & common leads reversed. A simple plug tester from HomeDepot was all I needed.
 

John From Detroit

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I had that problem too. I discovered that the plug I had used from my garage had the hot & common leads reversed. A simple plug tester from HomeDepot was all I needed.
The last trailer I bought the owner had made his own 20 amp adapter (Plug in v/s Twist lock) and did just that.. He made it out of an extension cord and he swapped the leads on that too so if you used his cord. No problem but I use my own 12ga cord wired properly so problem.. I fixed.
Folks the white wire goes to the shiny screw. the black to the copper Do I need to tell you the Green goes to Green? (Well the kid who wired my central air conditioner needed to be told that and he was supposed to be a professional).
 

whiteva

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RV TECH INTERVIEW:
Question 1: what is this? Answer: Screwdriver
2: Ya got One? Yep
3: Got any other tools? Yep, I can use my dad's
4: What is that? Camper it think.

OK, can you start work today as a Technician? Yep, but I can only work till 3:00.
No problem we're backed up with broken A/Cs.

Welcome to the crew, here is your tech certificate, ya gotta get your own frame.
 

Gary RV_Wizard

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Basically you have a short to ground in the 120vac system of the trailer. The challenge is finding it. One fairly common one is a water-soaked exterior outlet, but those are supposed to be on a GFCI-protected circuit and the GFCI should trip. But maybe your GFCI was replaced at some point. Or maybe somebody installed an outlet or gadget incorrectly and used a ground where a neutral should be.

I agree that the heater element in fridge or water heater is also a common ground short, but those are often high-resistance and don't result in that much voltage in the trailer skin. Worth checking, though.

A plug-in outlet tester will help you do a quick check of major wiring circuits.
 

Lou Schneider

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Heating elements of the fridge and water heater are both very good suspects. Plug into a ground fault receptacle. Does it trip it? This makes finding it easier. Start with unplugging the fridge cord on the backside of the fridge, flip off the water heater if you had it on. Process of elimination, just one item at a time. Make sure whatever you are checking is actually functioning at the time.

Charles
Turning off the circuit breaker will open the hot lead to the water heater but won't do anything to eliminate a ground fault if there's a neutral to ground short. You'll still trip a GFCI ibreaker even with the circuit breaker off.

The only sure way to eliminate something from contributing to a GFCI fault is to physically disconnect it from the incoming electric supply,both hot and neutral leads. This happens when you unplug the fridge, for the water heater youo have to physically disconnect both the hot and neutral lines where they connect to the water heater and see if the GFCI fault goes away.
 

Jim18655

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Unplug the shore power cable and check the voltage from the Neutral to Ground at the shore power receptacle. You should get a 1 or 2 volt reading at most. I suspect a bad bonding connection in the house panel, maybe a bad neutral connection to the transformer. A good ground to the RV from the house should drain the stray voltage away and keep you safe.
 

Isaac-1

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The fact that you are seeing so many different suggestions is due to the multiple things that can all cause these same symptoms.
 
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