I have read some threads, watch vids about this topic and still question the reasons for earth grounding off grid applications. I can understand the need for a structure that is naturally partially grounded as in a home on a foundation with rebar etc. My question is for a structure that is not grounded in anyway, as in a shed on pier blocks etc. It seems that the main reason is for equipment and service panels etc. Is there an actual benefit for personal protection?
Earth Grounding
- Thread starter Drew888
- Start date
DougfromdaUP
Solar Enthusiast
Absolutely! Grounding and bonding the panels is primarily done for safety reasons. If, for example, a lead should break and rest against a frame, that frame could have a potential of hundreds of volts to ground or adjacent panels. You don't want that.
Believe what the wise folks here say. There may be things in the code that protect against extremely unlikely events, but this isn't one of them. Ground for safety. (edited for clarity)
Believe what the wise folks here say. There may be things in the code that protect against extremely unlikely events, but this isn't one of them. Ground for safety. (edited for clarity)
Last edited:
Thank you for your reply. I understand the value of bonding the electrical components together In all applications. Without bonding none of the safety equipment, fuses, breakers etc would function if there was a short to a metallic component.
My question is specifically about earth grounding and personal safety/benefits for off grid. Is it possible that there are negative safety factors from earth grounding in an off grid application? Off grid applications have been around for a long time, but I wonder if some of the electrical techniques or theories are carry over from from on grid systems. Or is there different levels of off grid where some benefit at one extreme and no benefit at the other? Would a motorhome or trailer benefit from earth grounding?
The grid has a massive infrastructure and for that reason it is a huge liability. From a lightening strike or a short in the grid the earth ground is the last chance for the current to go to ground before the structures components. Also if there is a strike close to the structure the current flow can go to ground. Off grid non-grounded structures don’t have that issue.
My question is specifically about earth grounding and personal safety/benefits for off grid. Is it possible that there are negative safety factors from earth grounding in an off grid application? Off grid applications have been around for a long time, but I wonder if some of the electrical techniques or theories are carry over from from on grid systems. Or is there different levels of off grid where some benefit at one extreme and no benefit at the other? Would a motorhome or trailer benefit from earth grounding?
The grid has a massive infrastructure and for that reason it is a huge liability. From a lightening strike or a short in the grid the earth ground is the last chance for the current to go to ground before the structures components. Also if there is a strike close to the structure the current flow can go to ground. Off grid non-grounded structures don’t have that issue.
Done correctly there should be no negative safety factors. Earth grounding provides a solid reference point in your electrical system that guarantees that metallic equipment surfaces that you can touch will be at same potential as earth ground. In grid connected RV application this prevents a condition called hot skin where touching a door handle while standing on the ground causes a tingle or a shock. If your AC power system was fully isolated then there would not be a distiction of hot or neutral and you may have a condition where surfaces acessible to touch are at different potentials creating a shock hazard if you happened to touch something just right to complete that circuit. With clear hot and ground reference there would not be a possibility of this hidden shock hazard to exist because if equipment hot to ground fault were to occur it would cause a trip either via GFCI, circuit breaker or inverter overcurrent trip.
What if it was an off grid scenario RV application? Can’t all of the electrical/metallic components be grounded/bonded together to prevent shock without an earth ground? One of my concerns is that the earth ground field sets up a situation where an individual can be in a position to complete a circuit between the hot and anything that is an earth ground. The other would be that non-earthed bodies will not attract lightening.
They can. Bond them to neutral/ground of your inverter and RV frame and you got a floating ground reference inside your RV. But when you connect to shore power you have to connect your floating RV ground to electrical service ground. This is to make sure an equipment ground fault will not energize your RV frame and shock you when you are standing on earth surface while and touching it.
That will not prevent a lightning strike to your RV. Cars get struck by lightning too. The bolt of lightning traveled 1 mile from the sky, what is another 6 inch distance between a tire rim and earth for it? Nothing.
timselectric
If I can do it, you can do it.
- Joined
- Feb 5, 2022
- Messages
- 19,084
Electrical grounding is a personnel safety system.
Has nothing to do with lighting protection. That's a completely different system.
An electrical grounding system starts at the N/G bond. And then all exposed conductive materials are connected to it. So that anything you can touch, won't shock you. (Including the earth)
Has nothing to do with lighting protection. That's a completely different system.
An electrical grounding system starts at the N/G bond. And then all exposed conductive materials are connected to it. So that anything you can touch, won't shock you. (Including the earth)
Wouldn’t a floating/isolated ground be adequate or even better for a small off grid structure such as a shed? From my understanding vehicles, planes etc only get struck by lightening because they move in the way of the event. I see your from south FL, I grew up in Pompano and Ft Lauderdale. I remember many lightening storms down there. I would much rather be in a vehicle that was not earthed in a storm.
If the system and structure are isolated from the earth is there anyway a person can be shocked from the earth?
Conversely if the system uses an earth ground can’t a person now be shocked between the hot and anything that is earthed?
Eg. A shed that has a grounding rod installed and the electrical components are earth grounded. Next to the shed is a small garden surrounded by a fence comprised of a dozen metal posts and wire mesh. A person runs an extension cord out to the garden which has a section of the hot exposed. Unfortunately they touch the exposed wire and the fence completing the circuit. The current draw is relatively low because of the resistance between posts and earth ground, but still shocks the person. Also if the cord contacts the fence it will have current flow just as any device, but not enough current to trip the 15amp breaker
My point is that some structures have to be earth grounded because of how they are built, source of power and others it might not be as necessary.
A house connected to the grid that is somewhat grounded by design has to have all of the electrical component, plumbing etc earth grounded.
Last edited:
timselectric
If I can do it, you can do it.
- Joined
- Feb 5, 2022
- Messages
- 19,084
This is the exact reason for the grounding system.
Also, an extension cord being used outside. Should be protected by a GFCI.
Imagine this scenario. You have your floating ground system in your shed. Then one appliance develops resistive path to real earth which biases your floating neutral/ground into becoming hot with 120v ac in relation to real earth. So you are walking on wet earth and touch something connected to your floating ground. Zap you just completed the circuit. To make this scenario impossible you have to connect your floating ground to earth ground.
It can work in both directions. With a real earth ground you have a possibility of completing the circuit from hot to real earth ground. With a floating ground it would require an additional system short to real earth and than contact to the system neatral/ground.
I guess I think this logic could be an unnecessary carry over from standard grid practices because the grid is the source which is based on an earth grounded system and with off grid the source is not earth grounded.
It’s odd to me that there is an assumption that all current has an infinity for real earth. In a floating system there would be no current flow if the hot is real earth grounded. That is not true for the typical grid system because the structures real earth grounded and the source (grid) is also real earth grounded.
And that additional hot to real earth path can exist without you noticing until you get zapped. Better to eliminate that chance by earth grounding.
That would only exist if you had a hidden hot to real earth path.
timselectric
If I can do it, you can do it.
- Joined
- Feb 5, 2022
- Messages
- 19,084
I'm not sure why you are stuck on the word "earth".
The earth is just an extension of your grounding system. Not the source of it. You are not connecting your system to the earth. You are connecting the earth to your system. Everything that you connect to your grounding system. Is made safe for you to touch without being shocked by your system.
A floating electrical system, means it isn't grounded.
A floating ground, means that the system is grounded but not connected to anything substantial. Like the earth or structure or the vessel it's installed on.
Can you install and use an ungrounded system, yes.
But most of the appliances that you will be powering were designed to be used on a grounded system.
So you should only use appliances that are double insulated. And designed for an ungrounded system.
Whenever someone argues against a safety system.
The only option is to wish them good luck. And hope that they will only endanger themselves.
The earth is just an extension of your grounding system. Not the source of it. You are not connecting your system to the earth. You are connecting the earth to your system. Everything that you connect to your grounding system. Is made safe for you to touch without being shocked by your system.
A floating electrical system, means it isn't grounded.
A floating ground, means that the system is grounded but not connected to anything substantial. Like the earth or structure or the vessel it's installed on.
Can you install and use an ungrounded system, yes.
But most of the appliances that you will be powering were designed to be used on a grounded system.
So you should only use appliances that are double insulated. And designed for an ungrounded system.
Whenever someone argues against a safety system.
The only option is to wish them good luck. And hope that they will only endanger themselves.
Why, because there is several types of grounding. Grounding components together and bonding are not the same as grounding to a grounding rod. There are lots of vehicles and structures that use an isolated ground system. They are grounded, but not to the earth. I believe there is a possibility that sinking a grounding rod for certain applications is not only not needed, but less safe.
Electricity does not care about beliefs.
Madco
Solar Enthusiast
Tim makes a good point. There isn't anything particularly special about earth or "the earth". It is just happens to be most places simultaneously. Other than that, earth is just a big charge sink and a really poor conductor. However, it is a good enough conductor to establish a voltage reference for ungrounded conductors.
After going back and reading through this thread I think there is a misunderstanding of what I mean. I‘m trying to compare two fully grounded systems where all of the components and appliances are grounded to the service. All devices will function safely and any hot to neutral or ground will trip the breaker. The question is comparing one with and without a ground rod to the earth. Travel trailers using an ac system without an earth ground are safe. It is a very proven concept.
A grid connection requires an earth ground for specific reasons and the pros outweigh the cons. I know my question goes against conventional practices which are often a carry over for many reasons other than the utility. Consistency is usually the main reason. There are distinct differences between on grid and off.
So the question is for simple systems where the structure is not already grounded, is an earth ground an actual liability? In this application how does it add value? I have already pointed out that it requires only one failure in the system with an earth ground before it would result in shock and without it would require two failures. There are several reasons for this question. Are we making these systems more complex, expensive and less safe by using methodologies that were developed for other applications?
A grid connection requires an earth ground for specific reasons and the pros outweigh the cons. I know my question goes against conventional practices which are often a carry over for many reasons other than the utility. Consistency is usually the main reason. There are distinct differences between on grid and off.
So the question is for simple systems where the structure is not already grounded, is an earth ground an actual liability? In this application how does it add value? I have already pointed out that it requires only one failure in the system with an earth ground before it would result in shock and without it would require two failures. There are several reasons for this question. Are we making these systems more complex, expensive and less safe by using methodologies that were developed for other applications?
Last edited:
A good inverter with a ground neutral tie, often tying negative bat term to it as well, with an isolation transformer - protection isn't coming from the earth, it's coming from the concept of "ground" being a path for electricity back, to the tap on the transformer and back to the bat.
An inverter without an isolation transformer, throwing the center tap onto the a trailer shell and calling it ground could be dangerous.
Yes, it can be more dangerous, but on a quality system that ties the earth to neutral, you have electrostatic protection from actual earth, and grounding from the shell acting as a return path but actually being at a 0 voltage potential vs trashy inverters that float.
Grounding is a good thing on good systems, on systems that are not good...tricky.
An inverter without an isolation transformer, throwing the center tap onto the a trailer shell and calling it ground could be dangerous.
Yes, it can be more dangerous, but on a quality system that ties the earth to neutral, you have electrostatic protection from actual earth, and grounding from the shell acting as a return path but actually being at a 0 voltage potential vs trashy inverters that float.
Grounding is a good thing on good systems, on systems that are not good...tricky.
Electricity comes from chemistry - ionic flow. Earth has to be made part of a system in order for it to act as a electron sink. Good equipment does that by bonding ground and neutral with isolation between DC and AC, and a ground stake. Bad equipment can still be safe, and you'll make it less safe by throwing stakes everywhere or tying things to a trailer shell, electrifying things that shouldn't be and even have current flowing down the wrong things, inverter mounting hardware glowing red etc.
There isn't a general rule about the protections offered by a ground stake. It depends on the equipment used and what is sinking into the rod or using it as a reference. It can range from a lot of protection to you are smoking your inverter by laying an AC current ontop of DC - and electricity is flowing through an incorrect path for the inverter.
And like I wish inverters were all built in a safe way so it would never have to be a discussion.
There isn't a general rule about the protections offered by a ground stake. It depends on the equipment used and what is sinking into the rod or using it as a reference. It can range from a lot of protection to you are smoking your inverter by laying an AC current ontop of DC - and electricity is flowing through an incorrect path for the inverter.
And like I wish inverters were all built in a safe way so it would never have to be a discussion.
Last edited: