No grid grounding/bonding

[johnnysolar]

definitely misinterpreting the information

Aux ground rods are very important to include here but it talks specifically about grounding myths and "touch". Also, I was not pointing out the welding example , you started earlier. Play it for two seconds from that time stamp, that welding subject is over with and then "Fact: grounding doesn't protect against electrical shock.' You must have went way before 1:01:34. At this point I'm wasting your time and I'm sorry. Watching the videos both in entirety will help keep us all safe when working on our systems.

 

[timselectric]

I think that I see where you are confused.
Electrical grounding, does not mean connecting to earth. It pertains to connecting to the grounding system. (Which also has a connection to earth)
I really wish that the code board would revamp the nomenclature.
It would remove a lot of confusion by calling it a bonding system instead of a grounding system.
And only use the words ground and grounding, when referring to the connection to earth.
EGC = Equipment Grounding Conductor.
Should be changed to,
EBC = Equipment Bonding Conductor
But until it's changed, we can only repeat their wording.

PS: I can definitely see how people can get confused. Even the way Mike says it. Would easily be misinterpreted by someone without an electrical background.
In the video, when he says "grounding it doesn't make it safe". He's actually referring to earthing it. (At that particular moment)
Grounding, bonding, and earthing, are easily wrongly interchangeable.
And we all do it. The difference is understanding the meaning, behind the words in the context.

 

[smr.ruby]

~17.59 in the first video. The only way to make it safe is to turn it off. The only way to turn it off is to have an effective ground fault path for something that may become energized (eg metal case etc). Since you will be touching the ground and you may touch something energized if the two are either 1) forced to be at the same potential (bonded) or 2) allow stray voltage to drive enough (safely managed) current to trip your safeties then either way the equipment, puddle of water, etc is now "touch safe." So yes the point of grounding is to eliminate stray and unwanted voltages - aka make things touch safe.

 

[johnnysolar]

Edit for correction: Assuming you have a ground from the inverter to the main panel, any fault will travel back to the main panel in order to find its way back to the source.

? The original statement you had was why I posed the question and resources I did initially. It's fascinating how lethal the grounding subject can be.

 

[johnnysolar]

aka make things touch safe

Try to prevent electrical shock by providing a path to turn off/open the circuit = safe to touch, then that's that.

 

[smr.ruby]

Try to prevent electrical shock by providing a path to turn off/open the circuit = safe to touch, then that's that.

Yes AND to point #1 to bond the stray voltage to ground and eliminate potential/voltage differences.

If all you wanted was a path back to the source for your stray voltages to trip the overloads then technically they could all be bonded to each other and back to the source (aka Equipment Bonding Conductor per tim) but never to the ground, right?

But what if the stray voltage was enough to cause touch hazard but not enough to trip your overload? That is why you are also bonding the equipment to ground so there is no voltage potential between the ground you ARE touching and the equipment even if it isn't enough to trip. And then add GFI to have a device that can disconnect the load with less than circuit protection levels when there is a situation causing voltage potential difference between ground and equipment case, etc.

Per his cartoon guy pictures you are a parallel path back to the source but if there is even another parallel path (through ground) back to the source that is less impedance then you - you can't be shocked, current takes the lower impedance path and what is left over for you to take (as a path) is nil.

 

[johnnysolar]

But what if the stray voltage was enough to cause touch hazard but not enough to trip your overload?

This does not happen in a properly sized system (17:39-18:22)

This is close to related to your post, "doesn't grounding bring everything to the same potential? NO" (19:00-19:20).

Is the thing you mention not related myth 2 in the video? I think it is (36:00)

It's just worth watching the whole video, for sure. "Myth 3: Grounding brings everything to zero potential. This reduces touch and step voltage to a safe value." (38:17)

Not trying to challenge you, just the ideas as I'm reading them and seeing conflicting info, which again, could lead to death even if we think we are being safe.

 

[johnnysolar]

(If the inverter has an issue the fault will find its way along the EGC to the panel bond?)

Hi, sorry for gumming up your thread but I hope the info and discussion was helpful. As for the question above, I think the answer is "yes" but it at least has to be sized right. This video is a good place to start for that. Second, I would be careful expecting it to trip the breaker if you have two separate inverters if they share a same circuit breaker. For example, if my one of my two 6500EXs (I still have yet to commission the system) have a fault, I'm not entirely sure they would trip a normal breaker given their output power. I'm going to be using a GFCI breaker to feed the "main" panel. The GFCI will be in a single space enclosure, what you would use for a hot tub, then feeding the panel where the N/G bond will be. Now, I have not completed this project, one for laziness and two because design of stuff is taking a while. Is GFCI breaker a dumb idea? I have not sought out the answer yet. Design; One hiccup I'm having is if I mount both of my inverters on a metal frame, will they potentially energize the frame during some sort of fault or even regular operation? I still have yet to answer that and am trying to mix materials (mounting similar to how bus bars are mounted). I see one person on the forum with two of the same inverters mounted to a metal frame but I'm not sure if it could be done safer.... Anyway, I hope the video helps with at least conductor sizing. Those two other videos I posted earlier are a must-see in my opinion.

 

[smr.ruby]

This does not happen in a properly sized system (17:39-18:22)

Is the thing you mention not related myth 2 in the video? I think it is (36:00)

It's just worth watching the whole video, for sure. "Myth 3: Grounding brings everything to zero potential. This reduces touch and step voltage to a safe value." (38:17)

Not trying to challenge you, just the ideas as I'm reading them and seeing conflicting info, which again, could lead to death even if we think we are being safe.

Good discussion for for sure, my motive anyway

I've always liked the Mike Holt stuff and is "style" is to be very clear about the CORE reason/purpose/whatever - almost to the point of provocative sometimes - which is great because I think there are a lot of misconceptions (especially in electricity land) that come from lack fundamental understanding - aka they get built up from myth and misconception I guess.

an example: Myth #2 is "Current takes the path of least resistance to ground" FALSE. I believe what is is trying to point out here - as he did earlier in the video is that "ground" is not some magical current sink for a circuit. However, what we are talking about is "The majority of current takes the least resistance path back to the source" TRUE. And when there is potential that ground becomes part of the circuit (eg though you) it is going through ground to get to the source - the crux of what he is trying to point out. Not just arbitrarily though ground because it is ground and "ground" is a magical absorber of all unsafe current - but it IS a potential path back to the source which can be both a problem (shock you) and an opportunity (to get back to the source).

Regarding "if we bring a conductor back from the point of a fault to the source then we will always turn off a the protective device if the system is probably sized and configured." (17:39-18:22). I honestly have a hard time agreeing with that. This is only the case in a world with GFI on EVERYTHING. I don't know about your house but my (1998 construction) house absolutely does not have a GFCI on everything. And it is absolutely possible to have a faulty piece of equipment (frayed internal wire for example) that can cause current to flow back on the equipment grounding conductor that is not enough to trip the breaker - easy to prove and obvious. But it is at least flowing back to the source through the ECG not through you. Curious what others think but I don't think even Mike Holt would disagree with that even though that little comment he made - read verbatim - sure sounds that way to @johnnysolar 's point.

 

[johnnysolar]

I don't know about your house but my (1998 construction) house absolutely does not have a GFCI on everything

So this is not just a GFCI thing, 17:09 is precisely where he mentions how it works with regular breakers, so go back a bit from there. The right size grounding conductor is supposed to provide a path for over current to trip a normal breaker. We have not been talking about electrical outlets so far, and I just barely mentioned a GFCI breaker in my last post... but as for GFCI... That is a more sensitive thing as far as I know, where if it senses a slight change it trips immediately due to not enough current passing thru to trip the breaker but potentially it has the minuscule amount required to cause death. For instance, I have a bidet/ heated toilet seat. It sometimes trips the GFCI but not the circuit, why? Because biobidet makes crap bidets and the leak inside it, when you use the spray function, causes an alternate path somewhere and it's like, nope, GFCI pops. Hot tub, same same, if the heater starts leaking, for example, a few drops could touch its electrical box inside and bam, pops the GFCI breaker. A regular breaker would need over current to pop and in a hot tub people would not be having a good time being part of the over current path.

 

[johnnysolar]

Please pardon the misuse of acronyms in my last post, of there are any. It can be annoying to get that part wrong and be a sign of not knowing the fundamentals, which i think is a proper judgement should it be made.

 

[smr.ruby]

The right size grounding conductor is supposed to provide a path for over current to trip a normal breaker.

Don't agree. We are talking about a fault/stray voltage of potentially unknown cause. We don't know either voltage, current carrying capacity or impedance of this new path that is been created unintentionally. If a few strands of wire touch the chassis of a piece of equipment served by a 100amp breaker those strands themselves would melt before enough current was conducted to trip the breaker. That doesn't mean it wouldn't be enough to shock you though... The right size grounding (bonding) conductor certainly will cause a path for the current that is not through you though .

EDIT: the breaker is sized to protect the wire, not to protect you. With a sufficient enough fault (in his example 580 amps) it most definitely will trip.

 

[timselectric]

I'm going to be using a GFCI breaker to feed the "main" panel. The GFCI will be in a single space enclosure, what you would use for a hot tub, then feeding the panel where the N/G bond will be.

This won't work.
The N/G bond must be before the GFCI. For it to function properly and provide any safety.

 

[johnnysolar]

This won't work.
The N/G bond must be before the GFCI. For it to function properly and provide any safety.

So a ground fault inside the inverters would not cause the GFCI breaker to trip? I know they shut down on their own when there are issues. Anyway, I'm still finalizing research and will continue to verify outside of this thread too. (My 6500EXs will have the N/G bond screw removed)

. If a few strands of wire touch the chassis of a piece of equipment served by a 100amp breaker those strands themselves would melt before enough current was conducted to trip the breaker.

This scenario is different than what I was talking about also to which a ground rod is not the appropriate fix as far as I know, was that the suggestion earlier? Parallel circuits carry the same voltage, low amounts of current can kill, that's where my mind is at. While I am refreshing lots of this info from Mike I think I'm wasting your guys time because I wanna say I'm talking about system grounding? I don't know man. I just feel it is incomplete to say grounding is to make things safe to touch, because it's deeper than that on a fundamental level even though that is one of the practical outcomes, it should not be left to that or sought out to do for only that reason. To forget it simply not know the fundamentals of why it exists in the first place can lead to poor decisions executed on good intentions.

 

[timselectric]

So a ground fault inside the inverters would not cause the GFCI breaker to trip? I know they shut down on their own when there are issues. Anyway, I'm still finalizing research and will continue to verify outside of this thread too. (My 6500EXs will have the N/G bond screw removed)

A GFCI only protects what is downstream from it.
The inverters do have their own built-in protection.
But the GFCI must be downstream of the N/G bond. In order to provide any protection. It can't see the fault, if the fault doesn't bypass the GFCI.

 

[smr.ruby]

a ground rod is not the appropriate fix as far as I know,

Yes you are correct and that is maybe where the language is getting tripped up. And that was the point that you can't just stick ground rods everywhere (his example with the pole) and call it safe.

"A properly established BONDING and GROUNDING is the proper way to manage faults and keep things from shocking you." This requires bonding equipment with equipment grounding conductors AND grounding stationary systems where earth may be an alternate path back to the source. That all fair?

I just feel it is incomplete to say grounding is to make things safe to touch, because it's deeper than that on a fundamental level

Agree and I think the crux is both bonding and grounding. Tim said a "grounding system" keeps things touch safe and you were pretty adamant that is false. But I think it is generally understood that the grounding "system" includes EGC bonding and a properly managed ground path. Mike H was trying to point out that you can't just run a bunch of stuff to ground and call it good because ground is some magical sink. Here is an ironic possibility: Mike was speaking to electricians (and engineers) with years of sometimes misconceptions (mainly that ground is the magical current sink) and if you are new to all of this you actually don't come with those misconceptions so the points he was driving (hard) don't work the same for somebody without the same bad habbits(?) to correct? As an engineer around a around electricians I appreciate their greater field knowledge but both teams get caught up in lore and bad misconceptions.

 

[smr.ruby]

But the GFCI must be downstream of the N/G bond.

Moreover if you put the N/G bond downstream of the GFCI isn't the GFCI going to always see that as a ground fault and trip. I was actually thinking ironically he wouldn't be creating an unsafe condition because the GFCI would be tripping all the time

 

[smr.ruby]

then feeding the panel where the N/G bond will be.

Plus @jonnysolar there should be only one N/G bond and it should generally be in the main panel or incoming source. As discussed many times on here there are some decent reasons not to do it in the inverter (the real source) but rather in the main panel. your description makes it sound like you are putting it way down stream in a sub panel, no?

 

[johnnysolar]

GFCI would be tripping all the time

I forsee this being possible, yes ?. Not fully thought out, but I have the stuff from my old spa. I'll spin off a separate thread after I skim the forum and .... Retweet? you in it. Heh, still can't work forums perfectly. Sorry, OP, for dragging this out.

 

[smr.ruby]

@johnnysolar if you are still studying and learning (aren't we all).
Ben here has a some good practical videos of N/G separation and ground fault protection including one where traces down some stray ground current because a piece of equipment in his house is causing an undesired N/G bond . Effectively the same thing would happen if you have a downstream N/G bond you made on purpose where you shouldn't.

Here is one with maybe some more real world examples of all of these topics: N/G bonding, earth grounding, and equipment bonding(/grounding). Same topics as in Mike H video but with real household circuits and such.