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John Jarrett avatar image
John Jarrett asked

140 VAC between Ground and Neutral when on Grid/Shore Power with Brand New MultiPlus-II 2x 120V

Hopefully I can explain this dilemma well! Here goes. I am a fairly experienced electrician, not by trade, but have been trained and have done a lot of residential electrical work. Had a cheap sinewave inverter on my 5th wheel trailer and decided it was time to make things good and safe so ordered a MultiPlus-II 2X 120V 12 VDC inverter charger. Installed as per instructions and di review some YouTube videos to learn about any "gotchas". No problems during install other than I hate push pin connectors. Screws make more sense IMHO and easier.

In inverter mode/operation when the trailer is unplugged from grid power, i have proper hot, neutral ground conditions. I.E., 120 VAC from neutral to hot, and have no fault indication on a three lamp ground wiring fault outlet tester. When plugged into grid power (shore power), I have all three lamps lit on the three lamp outlet tester and have 120 VAC between neutral and hot, 120 VAC from ground to hot and 140 vac from neutral to ground on all of trailer outlets! The ground light on the tester, (usually the far left one and usually red in color) is very dim. When on shore/grid power, the GFCI breakers will not trip when testing them with the tester. When on inverter power, the GFCI breakers will trip when testing.

The Inverter/charger is installed in a 50 Amp 5th wheel RV Trailer. All four grid power wires in the trailer, neutral, ground, L1 and L2 were pulled from the trailer's breaker panel and wired directly to the inverter/charger input and done correctly. Please Note: INPUT, GRID Power (Shore) SIDE GROUND and NEUTRAL LIFTED IN CIRCUIT BREAKER PANEL and wired directly to input of inverter. All output (inverter) wires are correctly run back to copper ground to Ground Bus, neutral to neutral bar, L1 and L2 to respective breakers. The trailer AC Grid supply is a 120 VAC 30 Amp RV plug with a 30 Amp to 50 Amp RV converter cord that internally jumpers trailer's L1 and L2 and feeds both legs, (L1 and L2) with singular 120 volt hot. The system works great! Inverter works, switches between grid power and inverter instantly when plug is pulled and boosts power when getting close to the 30 amp set point. But this is quite a voltage between neutral and ground when on shore/grid power!

Building codes and common sense state zero electricity should flow from neutral to ground, maybe a couple volts in some circumstances. I would like zero (0) volts between neutral and ground at all times and in all conditions and GFCI outlets that will trip when tested or when needed. The input and output grounds and neutrals are attached in the panel correctly and appear tight and snug in the inverter charger.

There was a similar post to this one that stated that this is just the way it is! I have to question that as it just doesn't seem safe or right.

As a test, in case I did have a ground issue, I attached the shore power ground to the ground in the trailer's circuit breaker panel and the results were the same. I thought maybe I had some kind of floating ground or non existent ground.

Any and all thoughts would be most happily recceived.

John


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6 Answers
Kevin Windrem avatar image
Kevin Windrem answered ·

What do you measure at the shore power inlet? And also at the point where that inlet connects to the Multi input?

I would insure all safety grounds are connected together and not relay on looping through the Multi for a solid safety ground connection. I don't think that's your issue but it's just the right way to insure a solid safety ground everywhere.

You should not need to jumper L1 and L2 on the input of the Multi.The 120x2 models will work with just the L1 hot powered and in fact ignore L2 if there is no voltage between it and L1.

Many meters will measure a voltage with an open circuit. So verify you have continuity between safety ground and neutral when connected to shore power. Another way to test this is to place a load (am incandescent light bulb is good for this) between neutral and safety ground. If the bulb lights then you have a hot neutral coming in. If not you have an open circuit (probably safety ground). In the latter case, the voltage measured between safety ground and neutral with the bulb in place should be at or near zero.

BTW, having a few volts between neutral and safety ground is expected especially if the system has a heavy load. There will be voltage drop in the neutral but not in the safety ground that varies with current. Excessive voltage (more than can be calculated based on the load current, wire size and length) is a concern and should be tracked down and fixed.

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John Jarrett avatar image John Jarrett commented ·
Kevin,

I added a bunch of information/answers to your questions, and it appears to still be in moderation, yet my comment below asking about how long moderation takes, was posted immediately. It may show up but I found the issue!!! A bad ground going into the Victron! I checked those inputs and voltages a million times. All seemed snug in the push in wire connectors which proved again why I hate them. Seems all is good at this point in time.

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John Jarrett avatar image
John Jarrett answered ·

I need to add one detail regarding the tests of the GFCI outlets in the trailer.

When on grid/shore power using the plugin outlet tester the GFCI test button on the outlet tester will not trip the GFCI outlet. I can however push the GFCI outlet's test button and it will trip. I can plug in my wife's hair drier with a GFCI plug, push its test plug and it will trip it's GFCI circuit.

When on inverter power, the plug in outlet tester test button will trip the GFCI outlet. Everything works as it truly should only on inverter power.

Thanks again.


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John Jarrett avatar image
John Jarrett answered ·

Can someone tell me how long my questions and responses will be moderated? And the general time it takes? I am a newbe here and understand. Just curious.

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John Jarrett avatar image
John Jarrett answered ·

Kevin,

I thought I'd paste your reply and answer each afterward.

"What do you measure at the shore power inlet? And also at the point where that inlet connects to the Multi input?"

120 VAC at each point. 30 Amp 120 in and 120 VAC on each leg, L1 and L2 after adapter. Ground to L1 and L2 show 120 VAC, and neutral to L1 and L2 show 120 VAC. No voltage across neutral and ground at any point before going into the invert/charger. They are bonded properly at my main panel and I have continuity between them.

"I would insure all safety grounds are connected together and not relay on looping through the Multi for a solid safety ground connection. I don't think that's your issue but it's just the right way to insure a solid safety ground everywhere."

Tying neutral and ground beyond the main breaker panel, such as a subpanel, which technically an RV panel would be, is not recommended and is against current code. I have not tried that yet and have thought about it but if something is wrong with my inverter/charger it might fry it. I had a previous low cost high frequency inverter that I fried by inadvertently tying ground and neutral. It took a couple hours but it cooked it! I have already tied the incoming ground to the RV breaker panel ground before the inverter with no change.

You should not need to jumper L1 and L2 on the input of the Multi. The 120x2 models will work with just the L1 hot powered and in fact ignore L2 if there is no voltage between it and L1.

I did see and read that in the manual. I would have to add a special receptacle to do that. The adapters are for RV Parks that only have 120 VAC 30 amp service, or like my home when I added a 30 amp 120 VAC service for my old bumper pull RV trailer. I added that info to try and be as thorough in my issue as possible.

Many meters will measure a voltage with an open circuit. So verify you have continuity between safety ground and neutral when connected to shore power.

In checking all of my wiring going into the inverter charger, I do have continuity between ground and neutral. My main panel at home is properly bonded. I cannot check continuity with a VOM when on shore/grid power as I fear I will fry my VOM since voltage is present after (at the output and receptacles in the trailer), the inverter/charger. When the inverter/charger is turned off there is no continuity. I believe the Victron switches all of these lines, including neutral and ground depending upon whether it is just charging or inverting. When the unit is turned off, using the main output, there is no power supplied to the trailer. I have not tried checking when the Victron inverter/charger is in charge only mode. I'll report back on that too.

Another way to test this is to place a load (an incandescent light bulb is good for this) between neutral and safety ground. If the bulb lights then you have a hot neutral coming in. If not you have an open circuit (probably safety ground). In the latter case, the voltage measured between safety ground and neutral with the bulb in place should be at or near zero.

This is a great idea to test if bonding is the way to go. But I already know I have voltage across neutral and ground. That's my issue. I will do that and report back!

BTW, having a few volts between neutral and safety ground is expected especially if the system has a heavy load. There will be voltage drop in the neutral but not in the safety ground that varies with current. Excessive voltage (more than can be calculated based on the load current, wire size and length) is a concern and should be tracked down and fixed.

I do know and understand that a few volts, depending on several variables, can be seen between neutral and ground. But enough to light a neon bulb? Measuring 140 VAC? That's more than what I read anywhere else. Output of the inverter in both on grid and inverter mode between any hot and neutral outlet in the trailer measures 120 VAC.

And... boy am I trying to track down and fix this issue! I am starting to believe that I have received a defective/malfunctioning Victron. I have put in a service ticket but have not heard back yet.

THANK-YOU!

John

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Kevin Windrem avatar image Kevin Windrem commented ·
I did not mean to imply connecting safety ground to neutral anywhere beyond the service entrance. Yes that's against code and wrong.


(I've seen it done and in fact one inspector of festival stage sound and lighting power INSISTED they be connected together at the stage!!!! In sound circles it always causes problems with buzz so the illegal bond had to be removed after the inspector left.)

The light bulb test was to determine if a connection was floating which would have resulted in no current flow and the bulb not lighting. I have seen neutral at a HARD 90 volts due to a bond on the wrong tap of a transformer. Blew up a surge protector. Such an incorrect bond would light the incandescent light. A neon light would probably not draw enough current to make this test valid and might light even with a floating connection.

As you discovered, your fault was a floating ground and the voltage you measures was due to leakage. The incandescent light would have dropped this voltage to zero or close to it and would not have lit up.

I have accidentally connected my meter in ohms mode to an energized AC circuit without damage but that probably depends on the meter. When I do power tie-ins, I check for voltage between safety ground and neutral first then check for continuity. I have uncovered a number of receptacles with bad safety ground connections that way. I've only found one RV pedestal with a floating ground but others have reported this as a common problem. This typically causes the reverse polarity light on the EMS or the shore power breaker to glow but not light fully.


Any way, glad you found the problem. And as I said earlier, best to interconnect all safety grounds and not rely on looping through the Multi.

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John Jarrett answered ·

A bad ground going into my Victron was found to be the issue! In looking over the schematics of the ground relay and how this thing switches input current I knew it had to be a bad ground or neutral. Start at one end back to the other.. again but this time I pulled all the conductors out of the input, (I hate those push in connectors), reseated everything and now I have proper voltages at all outlets, no phantom volts, (about .5 volt... maybe), and I am happy.

Thank you to Kevin above as he gave me a couple really good suggestions and after trying some and do a test bond from ground to neutral at the trailers circuit breaker panel helped in figuring things out. Juist things you think are right but aren't but ideas to help tracing.

Also, the leaking voltage was more like 65 volts not 140. I have a lot of voltmeters but grabbed the cheapo give away Harbor Freight one. A couple of good meters showed about 65 volts.

Thanks!


John

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Kevin Windrem avatar image
Kevin Windrem answered ·

A word of caution: if you are measuring voltage between neutral and safety ground approaching a phase voltage, do NOT connect safety ground to neutral even as a test. If the fault is not a floating connection but an actual miswired source where leg voltage is on the neutral, you'll at least get a big spark and an upstream breaker will blow. In a situation where the system neutral is at phase voltage there might not be a circuit breaker in the path and shorting it to safety ground could burn wires.

Also, it is NEVER a good idea to connect safety ground to neutral outside of the service entrance. If you come across a floating safety ground the circuit should be powered down until the fault can be fixed. Should a hot to chassis fault occur without a solid safety ground, the skin of the device would have lethal voltage and current. Sinking a ground rod might reduce the voltage on the safety ground but it will NOT carry fault currents back to the service entrance.

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