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Unwanted or stray voltage from roof?


Mister Blu

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Have a couple of non contact voltage testers and happened to notice one of them started beating when I brought it close to the Ceiling.  

Checked it with the other NCV tester and it confirmed that there appears to be some mysterious voltage coming from/through the coaches ceiling in my Sunrader.

What could this be from?

Has anyone else experienced this?

Is it the fiberglass?  Is this something I should be concerned about?  

Not sure of the source of this phantom voltage. 

Please advise.

Edited by Mister Blu
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I can't remember the exact details right now. Something about the neutral (white wire) and ground (green wire) should not be bonded together, but the neutral should float

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Hmmm, fiberglass,  non contact tester??   Do you have a roof air or could the RV be wired for one or a 120V ceiling fan?  Any solar?  Fiberglass is an insulator, something else is happening.

 

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WME: Not certain what/where you are speaking to with concern to wiring.  

Are you speaking to the wiring in the converter/fuse box?  

Under the hood?  Along some run or other, to or fro?

Some time ago, I heard something about how the shell/body of an auto/rv can become charged.  Do not recall the context.  

jjrbus: No roof air.  Solar panel is not installed yet.  

Non-Contact Voltage Tester; one is a Klein (pen style), the other is on a clamp meter.  Both register some amount of voltage.  

It also is not only in one place, as with with a hot wire behind ceiling.   It seems to register within an inch or so from ceiling, along at least 20 square feet area.  

Strange indeed.  

Will try a few idea to see what happens.

Edited by Mister Blu
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If it's anywhere near where the air conditioner would be installed there are wires there. All Sunraders came AC ready even if they didn't have them installed. Try turning off your 110 circuit breaker in your power center. Also ceiling light wiring can be the charge.

Linda S

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The main AC power cord, that goes from the rv park/house plugin to the main RV fuse panel. In a house the neutral and ground wire are bonded together at the main fuse panel. In an RV the neutral should NOT be connected to the ground, it should float.

The first thing you need is a cheap polarity checker to verify that what your plugging into has correct polarity

 

 

 

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I made 2 assumptions on this,  one it does not have a metal roof and it does not have a metal frame.   Turn off power and see if it still senses electricity. 

I carry a cheap outlet tester and always check when plugging in at a new place.  Improper wiring under certain conditions can be fatal. Not recommending this tester or HD using it for an example   https://www.homedepot.com/p/Commercial-Electric-Tools-Outlet-Tester-Green-MS112H/206029154

You can also check metal frame of RV with multimeter, by touching + probe to frame and sticking negative in ground or to something metal in ground.

Think of the RV as a sub panel, a sub panel is not bonded, the ground and neutral are kept separate and only at the source, main panel, are they bonded. 

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Unplugged from a.c. Shore power, and unwanted voltage is still registering on both non contact voltage testers.

Also have found that it reads over the hole surface of ceiling.  Walls do not register, only ceiling.  

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Do you still have a roof rack and is it connected to you coaxe cable for TV. If so is there a power booster, 12volt connection behind wall plate. Only other thing I can think of that might charge the roof even though it would be very weak. Ya know maybe you should try disconnecting your battery. See if there's still anything there. Just wondering

Linda S

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Little tip on non contact testers they pick up static electricity. And they don't pickup DC frankly they are a little too sensitive but a good start for a real test with a real tester.

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I am confused. Has someone added an inverter to your Toy?  An inverter verts?  12V DC from battery to 120V AC.  

Those detectors do not detec 12V and if there is no 120 in the coach. It is some kind of a false reading. 

They also do not detect actual voltage, something to do with electrons?  HIgh tension lines in the area or microwave could set off detector but have no current,  it is sometimes found in wiring running in conduit.  Wire is unhooked but picking up from energized wires around it,  referred to as ghost current. 

If you have no inverter, try moving the RV a couple blocks away and test again. 

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Linda: I previously removed the aluminum roof rack.  

Maineah:  picked up stray, or ghost, voltage with two separate NCVT.   I do have a fluke 116 (real tester).

jjrbus:  no inverter to speak of.   Just the original converter.  

Unplugged from shore powere an dreading was still there.  As I am in the road currently, and no longer in the same spot, I will check I think again to see if it was merely picking up a ghost current from nearby wires. 

Interesting side note... Many years ago I was riding my longboard around town while using a NCVT as a signal light of sorts.  When I punch the button the red light would blink, made for a decent make shift turn signal.  One times, while under some overhead wires, the things start going of.  Led me to consider the potentially adverse effects of all the extra electrical currents humanity has strung all about.  

 

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This is likely worn out shielding on some cable or static charge accumulation.

First try measuring dc voltages -- use a voltmeter set at 20v. One probe at a chassis ground, touch in several suspect places. There shouldnt be any voltages. This is harmless but worth performing on an unknown or unexplored vehicle.

This isnt harmless if you arent careful. This following text also assumes no heavy wattage invertor like one designed to run any appliance -- you must have chased down all sockets, stuck a voltmeter set to 120v ac into all ac sockets and verified 0 volts.  You can now try a makeshift lightening protector. Unplug the convertor charger both ends -- it should plug into an ac socket one end and screw into two 12v dc locations the other end. Then take a single insulated cable, with exposed terminals, stick one into ground soil. Touch the other end where ucvt shows voltage or previously known/ suspected locations.  Measure current through the cable with an ammmeter. If there is any current in meaningful amperege steadily/rising and going to ground through this cable -- disconnect immediately, you have a mystery component generating voltage. More likely, there isnt any and the static charge wears off as coach is grounded. Wash the vehicle to reduce/dull exposed fibers that might be picking up static charge.

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I have and use NCVT you know how I test it? Rub my finger over it it it blinks it's working. They are only a test that something might be there. Inverters have a common ground both DC and AC. Your AC panel is a sub panel there is ground and a neutral they are not connected it is wired that way to avoid stray voltage on the ground and in less it's plugged in there is none this keep you from getting shocked opening the door for instance. As far as lighting is concerned the camper is a Faraday shield no ground will make any difference as far as protection.  

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