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Old 09-04-2017, 02:24 PM   #1
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1967 24' Tradewind
Bellevue , Washington
Join Date: Apr 2008
Posts: 31
AC 50volt shock

I pulled our '67 Tradewinds out of the shed to set up and check out after over a year of sitting. We have a 30 amp connection so the batteries stay charged. A chipmunk got in there over the winter.

As I was replacing the leaking plug on the water heater I touched the frame and got a small shock (when shore power was connected). I measured 50 volts from the frame to the earth. Weird number.

I hunted for frayed/chewed wires and found one of the white wires to the refrigerator which I replaced. This made me think some kind of current has run in the white side to attract the varmit...

I've been experimenting and testing between the D.C. Side and the AC side. Could use some knowledge to sort this out...

Test 1: with shore power attached and all of the circuits turned off I still get an AC voltage reading between the frame and the earth. (I am pushing the black wire on the multitester into the ground). I took the cover off the circuit panel and couldn't find any wires touching or frayed. I can't understand how there is any voltage when the main is off unless that circuit breaker is broken....

Test 2: I took the batteries out and disconnected the shore power. I found D.C. Power from the red (positive) battery cables to the frame of the trailer. How? No power source. I have an Intellipower 9000 with a Charging Wizard and thought maybe this device has power storage. I mean, even the green light on the Charging Wizard was flashing. The only thing I can think is there is a small battery for the power jack that is connected to the trailer light umbilical. I thought that particular battery gets charged from my truck and was separate from the trailer AC & DC systems.

I've found some electrical diagrams and thought I should try making one for my trailer. The PO did all the work and its very different than original.

Suggestions?
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Old 09-04-2017, 02:48 PM   #2
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If you measured voltage while the circuit breakers were off the problem is in the supply. What are you plugged into? Test test that supply circuit. If it is a 3 prong 120 volt receptacle use a plug in tester that will show faults.
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Old 09-04-2017, 03:55 PM   #3
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2017 30' Classic
Carlisle , Pennsylvania
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Hi

What you are seeing is pretty standard. A lot of electronic gear has filters on the input. They will put about 60V on an open ground. The current is not enough to kill you (usually ...) but you will notice it. Best guess is that you have an open ground somewhere. It may be the bonding of the shore power ground to the trailer body. It could be somewhere else. To run it down:

1) Shore power socket to known ground should read zero volts / zero ohms
2) Same on the ground pin on the end of the shore power cable
3) Same on the frame of the trailer

Likely somewhere on that list you will find an open circuit ....

Bob
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Old 09-04-2017, 04:20 PM   #4
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2002 30' Classic S/O
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"Test 1: With shore power attached and all of the circuits turned off I still get an AC voltage reading between the frame and the earth. (I am pushing the black wire on the multitester into the ground). I took the cover off the circuit panel and couldn't find any wires touching or frayed. I can't understand how there is any voltage when the main is off unless that circuit breaker is broken...."

Something is still connected to shore power. As uncle bob says, some designs of noise filters in power supplies (like your converter) will put about 60 volts on the ground connection of the power supply. It should be connected to your house power ground by the green wire system in your trailer. That ground should go back to the ground for your house through the 30A wiring (you do have a ground wire in that connection, right?) Even if that is wired correctly, the potential of the earth at the location of the trailer can be different than that of the house ground (typically at the meter) and may still give you a shock. The only way to prevent that is to drive a ground rod at the trailer and connect it to the trailer frame.

"Test 2: I took the batteries out and disconnected the shore power. I found D.C. Power from the red (positive) battery cables to the frame of the trailer. How? No power source. I have an Intellipower 9000 with a Charging Wizard and thought maybe this device has power storage. I mean, even the green light on the Charging Wizard was flashing. The only thing I can think is there is a small battery for the power jack that is connected to the trailer light umbilical. I thought that particular battery gets charged from my truck and was separate from the trailer AC & DC systems."

Power converters typically have large capacitors in them to smooth their output. They will store 12V for a significant period of time. Turn on a 12V light and it should discharge the capacitors. If the light illuminates, the converter is still powered which could be possible given that the trailer has been rewired. I'm assuming you don't get the shock if the shore power is disconnected.

Is that battery for the jack, or for the brakes? Sometimes the emergency brakes have their own battery, but that is more typical on things like boat trailers that do not have house batteries. Maybe the PO hooked it up to the jack instead.

Al
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Old 09-07-2017, 11:04 AM   #5
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1967 24' Tradewind
Bellevue , Washington
Join Date: Apr 2008
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Just so you know I didn't electrocute myself, HowieE gave a simple explanation I couldn't believe! At the moment, my supply is from a barn built in 2005. But I've learned that you guys on the forum are way smarter than me so I plugged in my electrical tester and, sure enough, there was an open ground in the barn outlet! I fixed it and now I get no shock from my trailer! I tested all my 110v outlets on the trailer and they are good except the exterior outlet which shows a flickering ground light on the tester. I tried cleaning the orifices on the outlet and still just get a faint light so I ordered a new outlet from VTS because I am anticipating something will break when I take it out to clean the wires inside the box. So the 110v system seems good
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