AC voltage bleeding to DC

[MadMaxWinny]

^ This! My guess is a faulty shore power service. Use the genset test to verify. Also get a polarity tester for your shore power pedestal (a must have, before ever plugging in). This happens all of the time in marinas, occasionally with fatal results.

[Ray,IN]

Re-reading all your thread; your reply #4 you said you turned off the main RV breaker, still measured AC voltage. That to me indicates that somewhere there may be a loose connection allowing a shore power hot wire to unintentionally touch something else. Do you measure AC voltage when shore power is unplugged. If not, that pretty much indicates a faulty shore power cord or between side of RV and RV main breaker panel.

Have you closely inspected all wiring connections, including plug ends?

[NormD]

I don't understand your Trickle Charger measurements. You originally measured zero volts from bolt to Earth with shore power disconnected, then measured again and this time found 18 volts between bolt and Earth with shore power disconnected. How was the Trickle Charger involved in the two measurements?

[Bobn1957]

If you are testing with your tongue, stop right now! This indicates you are out of your league with this problem, take it to an RV dealer! They will find the issue in short order.

[eyecando]

There is no way you can have 18 volts between the trailer frame and ground unless one of the grounds is open. It doesn't matter what breakers are turned on. This cannot happen unless one of the grounds is open circuited.

If you had 18 volts present with proper grounding, you would be tripping breakers somewhere.

Are you sure you are reading 18 volts or is it 18 millivolts?

[sirfallsalot]

Originally Posted by jerichorick

My first thought is the ground to the pedestal. Does the pedestal have a breaker associated with the outlet? If yes then the ground should be at the pedestal. If the ground is from the feeding service panel it may be so far away it is not grounding correctly... too much resistance.


My next guess would be the ATS if you have one. Make certain all the connections are tight and none at burned in this device.


Hope you find your problem soon.

I have the RV plugged into a grounded outlet at my home. What is an ATS?

[sirfallsalot]

Originally Posted by ldfeat

Try disconnecting from shore power then run the generator AC current and see if it does the same thing... Larry, 2014 Reyo P.

Good idea. Unfortunately the generator has been removed from RV. Rats ate generator wiring so I'm going to replace with Solar & use a small portable generator if/when needed. In this rig, the generator is only physically connected when one plugs the shore power cord into the female generator plug. So, removing the generator has no affect on A/C system since it's not plugged in.

[sirfallsalot]

Originally Posted by Bobn1957

If you are testing with your tongue, stop right now! This indicates you are out of your league with this problem, take it to an RV dealer! They will find the issue in short order.

I truly appreciate your concern. Thanks.

[sirfallsalot]

Originally Posted by NormD

I don't understand your Trickle Charger measurements. You originally measured zero volts from bolt to Earth with shore power disconnected, then measured again and this time found 18 volts between bolt and Earth with shore power disconnected. How was the Trickle Charger involved in the two measurements?

This really surprised me too. The trickle charger +/- leads were connected to the +/- terminals on van battery (the one that starts the engine), while the shore power cord was unplugged. In this config I measured the 18V to shore power GND at extension cord (which is on same AC circuit as shore power plug). In this config, I can feel a tingle on wet finger when standing on the ground. In theory the trickle charger should only provide DC volts, so it's unclear how it's injecting AC volts to the chassis GND (the bolt).

[sirfallsalot]

Originally Posted by eyecando

There is no way you can have 18 volts between the trailer frame and ground unless one of the grounds is open. It doesn't matter what breakers are turned on. This cannot happen unless one of the grounds is open circuited.

If you had 18 volts present with proper grounding, you would be tripping breakers somewhere.

Are you sure you are reading 18 volts or is it 18 millivolts?

18V AC, between frame and the GND terminal of extension cord plugged to shore/home power. Breakers trip based on high current, not voltage. This situation is very low current (high impedance) short somewhere, based on getting just a light tingle vs serious zap.

[jerichorick]

Originally Posted by sirfallsalot

Good idea. Unfortunately the generator has been removed from RV. Rats ate generator wiring so I'm going to replace with Solar & use a small portable generator if/when needed. In this rig, the generator is only physically connected when one plugs the shore power cord into the female generator plug. So, removing the generator has no affect on A/C system since it's not plugged in.

Oh my!

(Earlier question answer: ATS is Automatic Transfer Switch.)

If you have rodent damage to your wires all bets are off. You could very well have a hot wire touching some grounded area causing it to be energized.

If I were you I would unplug my RV, shut off the inverter and shut off all the circuit breakers in the rig. Make certain nothing is plugged into any outlet. Any AC appliance that can't be unplugged must be off and even disconnected.

Next, test each circuit from the circuit breaker to ground with a volt-ohm meter. You should have infinite resistance on the lowest ohm scale. If you read resistance trace the wires to see where the damage is.

[bigb]

Originally Posted by sirfallsalot

This really surprised me too. The trickle charger +/- leads were connected to the +/- terminals on van battery (the one that starts the engine), while the shore power cord was unplugged. In this config I measured the 18V to shore power GND at extension cord (which is on same AC circuit as shore power plug). In this config, I can feel a tingle on wet finger when standing on the ground. In theory the trickle charger should only provide DC volts, so it's unclear how it's injecting AC volts to the chassis GND (the bolt).

Is the trickle charger a 2 prong or 3 prong cord and plug?

[eyecando]

Originally Posted by sirfallsalot

18V AC, between frame and the GND terminal of extension cord plugged to shore/home power. Breakers trip based on high current, not voltage. This situation is very low current (high impedance) short somewhere, based on getting just a light tingle vs serious zap.

Thats the point. You cannot have 18 volts between two grounded circuits without high current which would trip a breaker. The impedance between the grounds should be less than 1 ohm which would produce currents greater than 18 amps.

If there is truly 18 volts between the trailer frame and the extension cord ground, this would indicate one of the grounds are open circuited, i.e. high impedance.

[bigb]

Some of the facts here are not making a lot of sense, I think knowing a few more facts might help, for instance does this happen at every hookup or only at one, and if so can you describe the hookup? One thing that has been in the back of my mind is a hookup with a faulty ground or neutral and possibly voltage on the ground of the hookup. When plugging in the RV, or the battery charger (if it has a ground pin) this could enable the voltage to then appear on the RV. This could be verified by testing from the hookup ground pin to the extension cord ground pin when the cord is plugged into a remote outlet. (checking from ground to ground on the hookup won't reveal it because they are at the same potential).
Another explanation is phantom readings which can be eliminated by placing a resistor such as an incandescent light bulb in series with the tester, but I have been reluctant to accept phantom voltage as the OP reports he can feel it.
We have to consider neutral voltage somehow getting to the RV. Since the neutral is not fused or breakered there is no protection on that side of the circuit, but seeing and feeling voltage while only the battery charger is connected doesn't make any sense, unless there is stray neutral voltage on the system ground being transferred to the RV any time it is also connected to the same grounding system.
If so, the integrity of the grounding conductor, neutral conductor and neutral to ground bond is in question. Please don't think a ground rod will fix it, safety grounding has to terminate at the common of the system that produced the current or it will not work. That's what the neutral to ground bond is for, and if there is a compromised neutral connection after the bond we can see neutral current back up onto the grounding system. Simply testing the RV at a different hookup could tell us if it is the RV or the service.

[eyecando]

It is normal to have a small AC voltage across the DC circuit, however it would normally be only a few millivolts or less with a modern filtered charger or converter. If an older charger/converter was used that had open capacitors I could see it causing a few volts of ripple voltage especially if the battery was open circuited. 18 volts AC seems very excessive. I would check that battery. I'm still wondering if the meter is not auto ranging to millivolts or maybe the meter is defective. The 12VDC positive circuit should not be connected to the AC circuit, however they do share the same ground. Maybe you are measuring between the 12VDC negative and the extension cord ground? If so, that would be expected with the current condition.

Again, 18 volts between the grounded trailer and the extension cord ground indicates one of the safety ground conductor circuits is open. I would look there first to solve the safety issue. That is likely not the only issue, but it is a place to start.

[sirfallsalot]

Figured this out so I thought I'd post what it was. Debug turned out to be really simple. I disconnected each AC circuit, one at a time, and measured impedance/resistance between power & neutral. The circuit with the Microwave had a 500 Ohm short. I unplugged the microwave & the short disappeared, as did the shock I got when I touched the RV while grounded. So, apparently I need a new microwave. Also, my original post was that I detected AC voltage across DC battery terminals. I guess that was just a byproduct of the discovered short. Thanks to all for your help and comments.

[bigb]

Originally Posted by sirfallsalot

Figured this out so I thought I'd post what it was. Debug turned out to be really simple. I disconnected each AC circuit, one at a time, and measured impedance/resistance between power & neutral. The circuit with the Microwave had a 500 Ohm short. I unplugged the microwave & the short disappeared, as did the shock I got when I touched the RV while grounded. So, apparently I need a new microwave. Also, my original post was that I detected AC voltage across DC battery terminals. I guess that was just a byproduct of the discovered short. Thanks to all for your help and comments.

Before you condemn the microwave try it on a different circuit using an extension cord if necessary, it is still possible it is a problem in the circuit. A microwave is a non-linear load so weird stuff can happen. I would try the microwave in the house too, if there is indeed something wrong with it and it is shorted to ground, and it trips the breaker in your house you will know there is a grounding issue in your RV since it didn't trip a breaker in the RV.

[sirfallsalot]

Originally Posted by bigb

Before you condemn the microwave try it on a different circuit using an extension cord if necessary, it is still possible it is a problem in the circuit. A microwave is a non-linear load so weird stuff can happen. I would try the microwave in the house too, if there is indeed something wrong with it and it is shorted to ground, and it trips the breaker in your house you will know there is a grounding issue in your RV since it didn't trip a breaker in the RV.

Thanks Brian. Testing with e-cord will be pretty easy. I'll try that.

[bigb]

I just re-read your post again, I didn't see where you said " measured impedance/resistance between power & neutral" Can you check between power and ground? Also 500 ohms at 120 volts will only produce 240ma which you will feel, and under the right circumstances can cause cardiac arrest, although it won't come close to tripping a circuit breaker. Still it does not make a lot of sense if it is between hot and neutral, this could even be a load from the unit your meter is "looking thru".
If there is indeed leakage of that amount between hot and ground it will trip a GFCI immediately.

[sirfallsalot]

I did that at same time I measured between Hot & Neutral. Open circuit between Hot (black wire) and GND. I actually measured at the wires of the Romex, which I disconnected from the panel before measuring). Measurements were taken with microwave plugged in, and then again with it unplugged.