Inverters - bonded/floating ground and reversed hot/neutral

[Terrapin]

As I said at the top of the thread. Grounding is a complicated multi-faceted concept.
Driving a copper rod into the ground is a different facet.
Now that you have opened the can of worms...

Electrical current tries to get back to its source.
Usually but not always via its polar opposite.

In the case of residential North American mains electricity the transformer is center tapped and this is called neutral.
The transformer center tap(neutral) is bonded to the planet.
Houses are also bonded to the planet at the service entrance.
And the ground conductor is bonded to the neutral conductor at the service entrance.
Having a neutral ground bond means that fault currents don't have to travel through the dirt to get back to the transformer.
That gives the current a path that is low enough impedance to trip the breaker and clear whatever fault condition was present.
The primary reason that everything is connected to the earth via a copper rod or similar is because that nature is teaming with electricity that gets onto our man made circuits.
A notable example is lightning.
Because the transformer is bonded to earth its even more important to have a neutral ground bond that carries fault current that might otherwise go through your body on its way back to the transformer.
Bonding your solar generator to the dirt could potentially make it more dangerous.
Are you more or less confused now?

PS. I think your help on our talks about this are raising awareness big time. I am starting to see a lot of questions centered around this in he waht's new section every time I come on.

 

[Terrapin]

Mike Holt:

https://www.youtube.com/results?search_query=mike+holt+electrical+

https://www.youtube.com/user/MikeHoltNEC

Grounding Myth:

Your honor, on the charges of believing myths I am accused of, I enter pleads of: Guilty, Guilty, Guilty, Guilty, Guilty, Guilty, and Guilty. holy crap!!!! ...... @smoothJoey The welding example at 24:03 when they are closing up is the ultimate example of your comment to me about grounding a generator potentially making things worse. He comments about lighing up the building, i thought of the out of balance ground current they talked about the whole time earlier...standing on that ground or potentially touching any conductor in contact withthe ground while holding a sweaty leather welding glove... Jesus... Tonight's aha moment. And so I say to you both..Thanks, I do finally understand what it is that I do not. My simple questions have all been case sensitive. Grounding is a a resistive variable And probably the only true grounding rod is at least 20' long, insulated to the bottom where that bottom electrode is of resistance low enough to carry the full circuits power to that 20' depth. So they are not circuit lighting rods and in fact are exactly the opposite. wow. just wow.

 

[John Frum]

Your honor, on the charges of believing myths I am accused of, I enter pleads of: Guilty, Guilty, Guilty, Guilty, Guilty, Guilty, and Guilty. holy crap!!!! ...... @smoothJoey The welding example at 24:03 when they are closing up is the ultimate example of your comment to me about grounding a generator potentially making things worse. He comments about lighing up the building, i thought of the out of balance ground current they talked about the whole time earlier...standing on that ground or potentially touching any conductor in contact withthe ground while holding a sweaty leather welding glove... Jesus... Tonight's aha moment. And so I say to you both..Thanks, I do finally understand what it is that I do not. My simple questions have all been case sensitive. Grounding is a a resistive variable And probably the only true grounding rod is at least 20' long, insulated to the bottom where that bottom electrode is of resistance low enough to carry the full circuits power to that 20' depth. So they are not circuit lighting rods and in fact are exactly the opposite. wow. just wow.

Please explain very succinctly.
I've never been able to sit through one his videos.

 

[FilterGuy]

Muddies the water? This was my intuiyive solution that seemed it should be as basic a part of trailer set up at camp as leveling the trailer. I even referenced seeing utility/fire trucks dragging grounding chains. How can this NOT be a thing when running any inverter system or DC over 12V.

Keep in mind that the ground scheem has two distinct purposes.

1) Making sure there is a low impedance path from a short-to-exposed metal that will trip a breaker. This is why the Neutral is bonded to the Equipment Ground wire and this does not need an earth ground to work.



2) Making sure no voltage differential builds up between the circuit and the surroundings. This has nothing to do with the N-G bond and is all about tying the circuit and metal to earth ground. By doing this, it ensures everything stays at the same relative potential to each other.


This thread is discussing problems around not having the N-G bond referenced in #1 above. Tying things to earth ground will not change the problem set.

Grounding Made simpler - Part 1: AC/houshold grounding

To get the paper, click on the orange button at the top of the screen. The subject of grounding is a complex, multifaceted subject, that is often treated as an after-thought but needs to be considered from the beginning of the design and build...

diysolarforum.com

 

[Terrapin]

Please explain very succinctly.
I've never been able to sit through one his videos.

My whole point is that this made me understand what I don't. so being more concise would be an endless loop of my own confusion. Please just accept, for now, my thanks at getting me to a place where I know what it is that is confusing me. If I could offer a genuine intelligent question that could solve a specific issue it's great to know you'd help. But I have some serious math issues caused by a condition that is similar to dyslexia but it centers around numbers. I do think I understand why my generic questions that deliberately avoided what others consider simply math have received the responses they have though. And for that I am very thankful to you and some others.

 

[Terrapin]

Keep in mind that the ground scheem has two distinct purposes.

1) Making sure there is a low impedance path from a short-to-exposed metal that will trip a breaker. This is why the Neutral is bonded to the Equipment Ground wire and this does not need an earth ground to work.

View attachment 43766

2) Making sure no voltage differential builds up between the circuit and the surroundings. This has nothing to do with the N-G bond and is all about tying the circuit and metal to earth ground. By doing this, it ensures everything stays at the same relative potential to each other.


This thread is discussing problems around not having the N-G bond referenced in #1 above. Tying things to earth ground will not change the problem set.

Grounding Made simpler - Part 1: AC/houshold grounding

To get the paper, click on the orange button at the top of the screen. The subject of grounding is a complex, multifaceted subject, that is often treated as an after-thought but needs to be considered from the beginning of the design and build...

diysolarforum.com

" This is why the Neutral is bonded to the Equipment Ground wire and this does not need an earth ground to work." FREAKING PERFECT for my level of abilities and understanding!!!! thank you!!!!!!!!!!

" This is why the Neutral is bonded to the Equipment Ground wire and this does not need an earth ground to work." ....And this seems critical so the imbalanced power won't use you, or a combustible environmental resistor that could heat up as a circuit to balance the difference, I think, if I get it to this point. But I am still way behind and will need to know some scenarios of where/how it could occur to really set it in my mindset. But TY tons...every question leads to looking for an answer. In this realm that's not so concrete my answers are not coming to the questions I am sseking answers too, but seem to be a weird randomized amalgam... but I have lived with me a long while so I know that'[s par for the course.. TY!

I suck as a student, never done well just learning results, I always seem to need to know the why of stuff and figure it out.....

 

[Bud Martin]

And that is also why the ground wire must be the same or larger gauge as the HOT/Neutral wire to carry the fault current and trip the circuit breaker.

 

[Terrapin]

And that is also why the ground wire must be the same or larger gauge as the HOT/Neutral wire to carry the fault current and trip the circuit breaker.

10-4 on that... Big arse copper braid. ? ?

That vid was the bomb Bud!!!!

 

[Bud Martin]

You will be surprised to see some of the imported equipment do not use proper wire gauge for safety ground wire inside the unit, let alone if they wire the Line and Neutral correctly.

 

[GXMnow]

Many old devices didn't check for a proper ground or a neutral bond. But as devices have become more complex with sensitive electronics controlling a lot of power, the need for properly bonded and grounded power has become more important.

We are talking about 2 different things here.

1) All metal housings that contain wiring should all be connected to the building grounding conductor back to the electrical panel where the disconnect is, and that should run to a ground rod from the main panel. The dual ground rods that many codes are now requiring, are still to be connected by a single wire to the ground bar in the main electrical panel. There should be no other ground rod in the system. This ground wire path throughout a build should be able to carry the current required to trip the break of the circuit running with it.

2) The neutral wiring going to all outlets and devices all need to connect back to the main panel neutral bar. These are the wires that are intended to carry the return current. If everything is operating correctly, there should be no current returning on the grounding conductors. The neutral should be bonded to the ground system at the first disconnect into the building. There should never be another point in the system where the neutral and ground connect.

Ground fault interrupters work by comparing the current on the hot wire to the neutral wire. As long as all of the current going out the hot wire is coming back on the neutral wire, it knows all is good and leaves the power on. If the balance between the two currents differs by just 60 milliamps, the device will shut off the power. A full floating power source such as a generator on rubber tires with no ground will not trip a ground fault unit because the current can only flow between it's hot and neutral. No neutral/ground bond, no ground fault detecting. A furnace with a microprocessor control board, a CNC machine, or an EV charger all need to see clean power with proper grounding. If they see a voltage potential between the neutral and ground, many of them will shut down to protect themselves as well as people that might touch the device. This is for equipment protection as well as human protection. An EV charger is a delicate device, but controlling many amps of current. Same with a CNC machine and the gas furnace. Any current on the chassis ground could destroy the electronics as well as kill people. The electronics test the grounding and may now power up if they don't detect a proper hot, neutral, and ground system. Many electric cars won't charge from a generator unless the neutral is bonded to ground, and it has a path to earth ground from a ground rod. Ran into that problem trying to charge a Nissan Leaf with my old 5,000 watt Coleman generator. It kept showing a power fault until I bonded the neutral and we used battery cables to jump the generator ground to a speed limit sign post. Bing, the car started to charge. Took an hour to get 8 miles of range into the car. Should have been faster, but we could only get it up to 2,000 watts of charge power before it would fault again. I think the generator frequency or voltage was changing too much at higher load. That was enough to get him so a charging station.

My guess is that the furnace is also checking the power system to ensure it is safe to open a gas valve and light a rather intense fire under the control of a small computer. My 10 year old Carrier furnace is microprocessor controlled. The start up sequence is pretty picky and it can set about a dozen different fault codes and not light up if anything is wrong. It actually measures the electrical impedance across 2 wires in the flame to determine if it is actually burning or not. I can see this failing to work if the unit is not properly grounded.

With the inverter having the 60-0-60 output, you can't just bond the -60 volt "neutral" to ground. If all of the electronics in the inverter are fully isolated from the case, you "MIGHT" be able to then connect that "neutral" to the neutral wiring of your house, but it is unlikely the battery side will be isolated. Even if the inverter case is floating from the battery wiring and the output leads, you may not be able to safely ground the inverter. Unless the inverter is fully isolated, which I highly doubt with a 60-0-60 output, then the battery terminals of the inverter would now be at 60 volts, with the output now being 0-60-120 volts. That is not safe. This puts the battery powering the inverter at 60 volts AC from ground and that could kill someone. An isolation transformer will fix this problem, or you may be able to get an inverter with a proper neutral for just a little more money.

When feeding a device in your home from a generator or inverter system, you should leave the neutral and ground wires still connected back to the main panel. Connect the neutral and ground of the backup power source to the house neutral and ground, and then the new hot wire from the inverter or generator to the hot input of the device. This is how a generator transfer switch panel works. I installed one similar to this at my old house for use with my Coleman genny.

Amazon.com: RELCONT Reliance Controls 306CDKN 6-Circuit Indoor Transfer Switch Kit 30 Amp 125/250 Volt Pro/Tran 2 : Tools & Home Improvement

Buy RELCONT Reliance Controls 306CDKN 6-Circuit Indoor Transfer Switch Kit 30 Amp 125/250 Volt Pro/Tran 2: Electrical - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

I had my furnace, refrigerator, microwave, a PC, some lights, and a TV on those circuits. Plug in the genny, start it up, and flip a few switches and I am back running during a power outage. But at my house now, I have a Schneider XW-Pro battery inverter feeding a sub panel for my essential loads. It is completely automatic if power fails it just starts inverting and runs the important loads in my home. And my solar can charge it when the sun is up.

 

[Terrapin]

You will be surprised to see some of the imported equipment do not use proper wire gauge for safety ground wire inside the unit, let alone if they wire the Line and Neutral correctly.

perfect, I love it when the cash i spend is out to kill me.. LOL

But seriously, so THAT"S why UL listings matter, now that you said it. ummm hell yeah.

Keeping my people safe is job one. This is so important to me. I still need to track down some possible theory or or forensic studies of exactly what goes wrong beside lighting strikes or falling high tension wires but you got my undivided attention because that thin wire getting hot inside a device is EXACTLY what could be the missing link to my big "why does this concern people question. That turns a short into a fire....

I actually have a buddy who is a a fire fighter who is the departments investigator, He's got to have something to tell from classes if not the field. Now I know what to ask.

yet again Thanks for your time.

Nice tidbit to add ?

 

[Terrapin]

Many old devices didn't check for a proper ground or a neutral bond. But as devices have become more complex with sensitive electronics controlling a lot of power, the need for properly bonded and grounded power has become more important.

We are talking about 2 different things here.

1) All metal housings that contain wiring should all be connected to the building grounding conductor back to the electrical panel where the disconnect is, and that should run to a ground rod from the main panel. The dual ground rods that many codes are now requiring, are still to be connected by a single wire to the ground bar in the main electrical panel. There should be no other ground rod in the system. This ground wire path throughout a build should be able to carry the current required to trip the break of the circuit running with it.

2) The neutral wiring going to all outlets and devices all need to connect back to the main panel neutral bar. These are the wires that are intended to carry the return current. If everything is operating correctly, there should be no current returning on the grounding conductors. The neutral should be bonded to the ground system at the first disconnect into the building. There should never be another point in the system where the neutral and ground connect.

Ground fault interrupters work by comparing the current on the hot wire to the neutral wire. As long as all of the current going out the hot wire is coming back on the neutral wire, it knows all is good and leaves the power on. If the balance between the two currents differs by just 60 milliamps, the device will shut off the power. A full floating power source such as a generator on rubber tires with no ground will not trip a ground fault unit because the current can only flow between it's hot and neutral. No neutral/ground bond, no ground fault detecting. A furnace with a microprocessor control board, a CNC machine, or an EV charger all need to see clean power with proper grounding. If they see a voltage potential between the neutral and ground, many of them will shut down to protect themselves as well as people that might touch the device. This is for equipment protection as well as human protection. An EV charger is a delicate device, but controlling many amps of current. Same with a CNC machine and the gas furnace. Any current on the chassis ground could destroy the electronics as well as kill people. The electronics test the grounding and may now power up if they don't detect a proper hot, neutral, and ground system. Many electric cars won't charge from a generator unless the neutral is bonded to ground, and it has a path to earth ground from a ground rod. Ran into that problem trying to charge a Nissan Leaf with my old 5,000 watt Coleman generator. It kept showing a power fault until I bonded the neutral and we used battery cables to jump the generator ground to a speed limit sign post. Bing, the car started to charge. Took an hour to get 8 miles of range into the car. Should have been faster, but we could only get it up to 2,000 watts of charge power before it would fault again. I think the generator frequency or voltage was changing too much at higher load. That was enough to get him so a charging station.

My guess is that the furnace is also checking the power system to ensure it is safe to open a gas valve and light a rather intense fire under the control of a small computer. My 10 year old Carrier furnace is microprocessor controlled. The start up sequence is pretty picky and it can set about a dozen different fault codes and not light up if anything is wrong. It actually measures the electrical impedance across 2 wires in the flame to determine if it is actually burning or not. I can see this failing to work if the unit is not properly grounded.

With the inverter having the 60-0-60 output, you can't just bond the -60 volt "neutral" to ground. If all of the electronics in the inverter are fully isolated from the case, you "MIGHT" be able to then connect that "neutral" to the neutral wiring of your house, but it is unlikely the battery side will be isolated. Even if the inverter case is floating from the battery wiring and the output leads, you may not be able to safely ground the inverter. Unless the inverter is fully isolated, which I highly doubt with a 60-0-60 output, then the battery terminals of the inverter would now be at 60 volts, with the output now being 0-60-120 volts. That is not safe. This puts the battery powering the inverter at 60 volts AC from ground and that could kill someone. An isolation transformer will fix this problem, or you may be able to get an inverter with a proper neutral for just a little more money.

When feeding a device in your home from a generator or inverter system, you should leave the neutral and ground wires still connected back to the main panel. Connect the neutral and ground of the backup power source to the house neutral and ground, and then the new hot wire from the inverter or generator to the hot input of the device. This is how a generator transfer switch panel works. I installed one similar to this at my old house for use with my Coleman genny.

Amazon.com: RELCONT Reliance Controls 306CDKN 6-Circuit Indoor Transfer Switch Kit 30 Amp 125/250 Volt Pro/Tran 2 : Tools & Home Improvement

Buy RELCONT Reliance Controls 306CDKN 6-Circuit Indoor Transfer Switch Kit 30 Amp 125/250 Volt Pro/Tran 2: Electrical - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

I had my furnace, refrigerator, microwave, a PC, some lights, and a TV on those circuits. Plug in the genny, start it up, and flip a few switches and I am back running during a power outage. But at my house now, I have a Schneider XW-Pro battery inverter feeding a sub panel for my essential loads. It is completely automatic if power fails it just starts inverting and runs the important loads in my home. And my solar can charge it when the sun is up.

Hey sorry it turns out I seem to have hijacked your thread big time... I actually was dealing with these guys helping me try to understand a travel trailer grounding wiring topic I started elsewhere. Your OP here shed some light on what they had tired to say so I jumped here referencing that. It was all me asking them to help me here.

As for this post of yours, you hit the nail on the head about GFCIs... that was stirring in the back of my brain all during this. I am still going to need a bunch of time digesting it all but that particular point of what trips them is pretty cool and not outside what I think I might get in the big picture, so thanks for adding that especially since it was me who was so far off topic here.

 

[John Frum]

But I have some serious math issues caused by a condition that is similar to dyslexia but it centers around numbers. I do think I understand why my generic questions that deliberately avoided what others consider simply math have received the responses they have though. And for that I am very thankful to you and some others.

I thought I kept my part of this math free.
As I said before, grounding is big multi-faceted and confusing topic.
My suggestion is to start with the following link and find answers for the questions I posed.
I think that will help you gain a practical understanding of the bits you need.

UL-458. What's the worst that could happen?

OK, so people have been trying to help me out with an inverter to tie into an existing camper's AC system. I have read quite a bit of technical info, and I do honestly believe there is some reason why you shouldn't just plug your shore power into your inverter. But I just haven't wrapped my...

diysolarforum.com

Also @FilterGuy's description with diagram was good and succinct and went to the crux.

Inverters - bonded/floating ground and reversed hot/neutral

As I said at the top of the thread. Grounding is a complicated multi-faceted concept. Driving a copper rod into the ground is a different facet. Now that you have opened the can of worms... Electrical current tries to get back to its source. Usually but not always via its polar opposite. In...

diysolarforum.com

 

[FilterGuy]

If the balance between the two currents differs by just 60 milliamps, the device will shut off the power.

I believe they pop at closer to 5 or 6 milliamps of differential current.

Ground fault interrupters work by comparing the current on the hot wire to the neutral wire. As long as all of the current going out the hot wire is coming back on the neutral wire, it knows all is good and leaves the power on.

They are actually more elaborate than that. Yes, they compare neutral and hot and trip if there is a difference. However there are obscure cases where the differential current can be near zero but still have current on the Equipment Grounding conductor. To detect this they do some tricky stuff with oscillation circuits that will detect a current on the Equipment Grounding Conductor and pop when it is detected.

One of the problems of GFCI in the past is that the electronics inside could fail and there was no indication that they no longer offered protection. A lot of the newer GFCI circuits actually run a self-test every so often and if the test fails they won't conduct the power. (I do not know how the self test works)

 

[FilterGuy]

Also @FilterGuy's description with diagram was good and succinct and went to the crux.

That diagram was one page from a series of 4 papers that I put together to try and explain grounding in a simpler way. (I tried to do it in one paper but it got too long. Even simplified, grounding is a big subject.) The first one is here and it has links to the other 3:

Grounding Made simpler - Part 1: AC/houshold grounding

To get the paper, click on the orange button at the top of the screen. The subject of grounding is a complex, multifaceted subject, that is often treated as an after-thought but needs to be considered from the beginning of the design and build...

diysolarforum.com

If grounding is confusing to you, I encourage you to study the subject and keep asking questions. Grounding is a key part of safety and getting it wrong can have dire consequences.

 

[John Frum]

That diagram was one page from a series of 4 papers that I put together to try and explain grounding in a simpler way. (I tried to do it in one paper but it got too long. Even simplified, grounding is a big subject.) The first one is here and it has links to the other 3:

Grounding Made simpler - Part 1: AC/houshold grounding

To get the paper, click on the orange button at the top of the screen. The subject of grounding is a complex, multifaceted subject, that is often treated as an after-thought but needs to be considered from the beginning of the design and build...

diysolarforum.com

If grounding is confusing to you, I encourage you to study the subject and keep asking questions. Grounding is a key part of safety and getting it wrong can have dire consequences.

I think I have a fairly decent handle on it.
Have I said anything that indicates that I don't?

 

[FilterGuy]

I think I have a fairly decent handle on it.
Have I said anything that indicates that I don't?

Sorry....the comment was not intended to be to be directed at you. I can see how it could easily be miss-interpreted. I was just trying to expand on your reference to the diagram. Your comments have all been spot on. My comment was more a general comment to anyone that might be confused by grounding.

 

[time2roll]

1. Tested on HandyPowerX. As soon as I plug it in the protection light came on, and the inverter power shut off. Big time fail.

How can I make my 2 devices work? I’d prefer to have the Handy Power X work as that will last a long time on a tank of gas.

Back to the OP....

With the PowerX, what did you plug into what? The PowerX has a protection light? What does the PowerX manual say about this light?

Have you tried to power something simple like a hair dryer on low heat?

 

[John Frum]

Bonding your solar generator to the dirt could potentially make it more dangerous.

The reason its potentially more dangerous is because the ground pin on a 3 wire electrical appliance cord does not have any electrical connection to the solar generator.
So any fault current must go through the dirt to get back to its origin.
A human body could easily be part of the path back to the origin.

 

[harrymanimus]

Back to the OP....

With the PowerX, what did you plug into what? The PowerX has a protection light? What does the PowerX manual say about this light?

Have you tried to power something simple like a hair dryer on low heat?

Here are some things I have used my handy power x with. Air compressor, coffee maker, space heater, charging my Eco flow. The space heater takes 1500 watts on high and it seemed to do fine with that. The protection looks like it's for under voltage and over voltage from the battery / alternator. Or probably if it detects some other error situation. Something interesting that happens with my Chevy traverse is that if I don't have a load on the inverter it goes into an over voltage situation and then the protection kicks on. And I have to restart it. Annoying but seemingly if I have something plugged in it won't do that.