Complete Off Grid Grounding??? some Questions

[WYtreasure]

Check out Mike Holt's videos on youtube. He has some good general grounding specific videos, and I believe even some that are specific to ground loops, and to PV array grounding. He is a good explainer, and it may be that your learning style connects more with his presentation than the written resources.

Here's some more current information about PV Systems and the NEC in the US. It's a video>

MIKE ROCKS!

 

[BlackWaterPark]

2010 article referencing the 2005 NEC ocassionally. Much has changed since 2005 code and 2010. The 2021 NEC sould be consulted with re: (PV) Sysyems in the US.
It is interesting how the codes are being refined, but info in this article may not be appropriate for building (PV) systems today in the US.

I was more interested in the difference between stateside and non US view on grounding really. When I say mine system is ungrounded, that's really to say it's a floating ground which I've never had an issue with (not the definitive form of data conclusion, I'm aware, but valuable nonetheless) but have highly likely avoided an issue, which I've seen happen to 2 other systems in my area (and heard from others experiences). It is for this reason why I'll never use an earth rod, unless something happens which forces me to change my mind on it. I've read fairly extensively on the subject, and will scrutinize your material as well, so it's appreciated for sure...there's always something that can be discovered somewhere that I didn't see before.

 

[12VoltInstalls]

Would adding a ground rod or connection to ground (which I don't believe exists at this time) 100 feet away, at the house,
create a "GROUND LOOP"?

I don’t believe so.
IIRC if you are grounded at the panels there’s “supposed to be” a conductor from the panel ground rod to the ground rod at the house.

Nevertheless an off-grid system references the source - inverter or generator- bare/ground for the safety ground. For operation an earth ground is not necessary (for successful operation).

EDIT: just watched the video. Excellent!

 

[RandyP]

.....but have highly likely avoided an issue, which I've seen happen to 2 other systems in my area (and heard from others experiences). It is for this reason why I'll never use an earth rod, unless something happens which forces me to change my mind on it. ............

What was the issue that you speak of here ?

 

[RandyP]

........ When I say mine system is ungrounded, that's really to say it's a floating ground which I've never had an issue with ..........

In the US, RV's (mobile electrical systems) use the chassis as a grounding electrode, per the ANSI RVIA standard for RV electrical systems and NEC NFPA Code for RV electrical systems.
This results in the mobile electrical system that is grounded, but its a floating ground system (its grounded to the RV chassis, not a grounding electrode in the earth)

 

[BlackWaterPark]

What was the issue that you speak of here ?

I had posted earlier in the thread about nearby lightning strike/and or ground lightning being about to travel into the system via the ground rod, and subsequently damaging the system. To sumise; a 100% off grid neighbor had an issue where his inverter (Samlex pst600) and his dsl modem went the way of the blue smoke simultaneously directly after a nearby strike. The only thing which was connecting his cabin and particularl his electrical system (on piers, mind you) to the ground was a 8' copper grounding rod. This might be a misunderstanding on my part about how lightning in relation to grounding rods work. Conversely, I have had nearby strikes actually travel into my house via what I can only assume was my exterior black iron LP manifold pipe and arc right off my LP stove, mere feet from my body (not a forgettable thing), but my system was unscathed, and I do not have a grounding rod. The only thing, as my house is on sonotubes as well, which brings the outside into the inside is the LP piping, and underground, the black plastic water pipe. It's a strong correlation to me, but if I'm errant in my thinking, I should like to be set straight. That I've heard other people with similar stories helps to reinforce, though second hand examples they be.

 

[RandyP]

Basics:

 

[12VoltInstalls]

its a floating ground system (its grounded to the RV chassis, not a grounding electrode in the earth)

I could be wrong (re: terminology definition via NEC) with the lingo but when I hear “floating ground” or “floating system” I think of three things:
1) in a DC system with poor or failed neg(-) connections where the pos(+) finds any available path of less potential creating an unintended circuit (car dashboard flashes with left blinker, radio only works if boat running lights are on, etc)
2) designed features automotive electrical (primarily from the 70s through the 90s) where two filament bulbs and single filament bulbs change function based on a switch or relay (single filament side marker flashes with blinkers, and the front marker doesn’t illuminate if directional is on). I suppose this could be done other places than just automotive.
3) AC electrical in a house or RV where the neutral is ’open’ in reference to bare/green/ground, or a device like an inverter that does not incorporate that reference by design would be described as “floating.”

Technically a vehicle/RV that should reference the chassis and batt(-) and is connected in that way does not have a ‘floating ground’ per se; an actual metal ground/earth rod driven into the earth’s crust is not the distinguishing feature of a floating ground. I believe the “floating ground” terminology is limited to those three scenarios.

Hopefully one of the engineers or smart people here can develop on this.

 

[BlackWaterPark]

Technically a vehicle/RV that should reference the chassis and batt(-) and is connected in that way does not have a ‘floating ground’ per se; an actual metal ground/earth rod driven into the earth’s crust is not the distinguishing feature of a floating ground. I believe the “floating ground” terminology is limited to those three scenarios

I've seen this very thing debated amongst the various electrical gurus across multiple forums. Perhaps it's a matter of lexicon disagreement, I don't know. I'm clearly not an EE (though apparently many of them do not agree upon then terminology either), but the way I've always understood it was the example Zil tendered earlier in the thread.

 

[Zil]

There are problems of understanding when we use the same alternating current definitions when referring to direct current systems.
Direct Current has positive and negative. Alternating current has Hot#1, Hot#2, Neutral, and Ground often called Earth. (Talking about USA single phase ac.) Most commonly, "Floating Ground" is a term used in alternating current. It refers to a condition where the Neutral is not connected to the Ground. Therefore there is no neutral. Each line is Hot. And it matters not in which direction the wires are connected. In a grid tied system this is a serious problem and must be corrected.
Off Grid! With an Floating Ground Inverter or single use Generator the 'ground reference' never returns to planet earth, but only to the device case. We can connect one hot to the case thus create a Neutral wire. Some inverters and generators have this connection. In a RV we can connect the inverter case to the chassis and create a Ground reference of the metal vehicle.
Real electrical engineers please correct or clarify my MSO.

 

[RandyP]

MSO. In a total off-grid system. The ac distribution within the structure doesn't need any rod driven into the earth. That rod does nothing in a off-grid system. The only ac "ground" reference is back to the inverter.
Using earth rod connections to solar frames will provide some lightning protection. There can be a case made for connecting the solar panel negative to the lightning ground rods.

Lightning protection is provided by NFPA section 780.
The NEC electrical System required grounding does not provide any lightning protection.

 

[Zil]

RandyP. can you provide a link to NEC that addresses off-grid electrical system 'grounding'. especially inverters if available? thanks

 

[RandyP]

RandyP. can you provide a link to NEC that addresses off-grid electrical system 'grounding'. especially inverters if available? thanks

I may find a link to NEC requirement for off-grid RV Electrical System grounding. Will that answer your question ?

 

[Merlin]

Thank you all of you for the support again!!!

I attached a jpeg here to make you a Picture of my Situation. Hope its good enough explained.

Ungrounded Electrical Systems! Ungrounded photovoltaic (PV) systems? What is the world coming to?

iaeimagazine.org

Thank you,
My guessing is that it would be ok in a normal World without a grounding. ... Today just sell more stuff for that Building Code ....
just because it is written in a code does´nt mean at the same point its right and true. Most things are better they are not written in a rule.

 

[RandyP]

I'll do the RVIA LV ANSI Standard 2000 edition first, then tie it back into the NEC.

.

 

[Merlin]

Merlin are you in the USA or some other country?

I am not smart enough to know if we are or are not leading Merlin in the direction of a "GROUND LOOP".
I have a similar issue with my own build and hope to see the perfect solution reached in this thread.

What voltage, AC or DC, is traveling 100 feet to the house? I found this in another thread and I believe you are running 196 volts DC:
"I am fine because I need to go just 80 ft with 4S - 3P, 196V, 34 Amp and have just a lost of 1.55%"

Merlin says there are "ground spikes out of metal" near the panels BUT the house is not grounded.

I am assuming there are 2 wires, PV +/-, between the array and the house.

Would adding a ground rod or connection to ground (which I don't believe exists at this time) 100 feet away, at the house,
create a "GROUND LOOP"?

I am assuming the charge controller, inverters and AC distribution panel are in the house.

By the way i am located in Canada not in the USA.

And no, My Home doesn't have an Grounding at the moment!

 

[Zil]

I'll do the RVIA LV ANSI Standard 2000 edition first, then tie it back into the NEC.
View attachment 78910
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View attachment 78912

Thanks, Randy. That is the practice I follow and recommend in my posts.

 

[RandyP]

.......................
Off Grid! With an Floating Ground Inverter or single use Generator the 'ground reference' never returns to planet earth, but only to the device case.

Have you considered those who use a single generator with a metal platform/structure, and set that generator on the earth surface, adjacent to the RV, to reduce generator noise and vibration on the RV. This generator sitting on the earth surface may be referenced to earth for its ground, thereby referencing the RV to earth ground. Could this result in hot skin touch potential RV to person standing on the earth ?

We can connect one hot to the case thus create a Neutral wire. Some inverters and generators have this connection. In a RV we can connect the inverter case to the chassis and create a Ground reference of the metal vehicle.
Real electrical engineers please correct or clarify my MSO.

Inverters Listed for use in RV's (mobile electrical systems) requirethe ground lug on the case to be run to the RV chassis. Manufacturer instructions stand first, before any code requirement. The NEC requires use of a UL listed inverter in RV's in the US.

Therefore I do not see how you can have a code complaint RV in the US without including a chassis ground to the inverter case. There are nuances for pass thru inverters when the Shore power supply is required to provide the electrical system ground and ground the chassis, but when the inverter is turned on to supplement or provide all 120/240v ac power to the rv, there is a ground path relay that provided chassis ground to the inverter electrical system (shore power ground is left open, inverter chassis ground is closed.

 

[12VoltInstalls]

This generator sitting on the earth surface may be referenced to earth for its ground, thereby referencing the RV to earth ground

Do you think that your body is of a lesser or greater resistance than the generator frame?
1) Electrical voltages seek the most available path(s) back to their source
2) if wired properly the RV should be have the N/G automatically or manually disconnected from the on-board circuits when the transfer switch or cord is moved from one source to another. So your body completing a circuit to G/ground/bare/green/earth shouldn’t ever occur.
3) GFCI breakers are not so expensive that one couldn’t incorporate them if you think there’s a problem. Then the only unprotected part of the circuit is the generator cord to the transfer switch

 

[Zil]

Have you considered those who use a single generator with a metal platform/structure, and set that generator on the earth surface, adjacent to the RV, to reduce generator noise and vibration on the RV. This generator sitting on the earth surface may be referenced to earth for its ground, thereby referencing the RV to earth ground. Could this result in hot skin touch potential RV to person standing on the earth ?

Inverters Listed for use in RV's (mobile electrical systems) requirethe ground lug on the case to be run to the RV chassis. Manufacturer instructions stand first, before any code requirement. The NEC requires use of a UL listed inverter in RV's in the US.

Therefore I do not see how you can have a code complaint RV in the US without including a chassis ground to the inverter case. There are nuances for pass thru inverters when the Shore power supply is required to provide the electrical system ground and ground the chassis, but when the inverter is turned on to supplement or provide all 120/240v ac power to the rv, there is a ground path realy that provided chassis ground to the inverter electrical system (shore power ground is left open, inverter chassis ground is closed.

The '..metal platform/structure..' would have much too much resistance to the earth to be considered electrically grounded. Maybe if sitting in a puddle of water, but that is doubtful. If the power cord feeding the RV has the required 'green' wire connected to the chassis, the RV skin is referenced to the generator and will be no danger to the personnel.
Samlex inverter is ETL to UL Standard and approved for use in the USA.. It is installed in RVs. It is designed for RVs. Quoted from manual;;
"When using the inverter in a mobile RV, connect a 10 mm2 or AWG #8 insulated stranded copper wire from the above equipment grounding lug to the appropriate ground bus of the RV
(usually the vehicle chassis or a dedicated DC ground bus). The connections must be tight against bare metal. Use star washers to penetrate paint and corrosion.

This conversation is about Off-Grid systems and has no relevance to Shore power systems. I can not find a reference in the NEC about off grid inverters. Is there any NEC reference to RVs?