ddawg16
Well-known member
This was posted on another forum.....outstanding video and should be watched by all..
Grounding Myths
- Thread starter ddawg16
- Start date
MrMark
Well-known member
excellent. Should be mandatory viewing before posting on electrical forum.
compaddict
Well-known member
Thanks for that.
Kevin C
Well-known member
Many people want to see things in black and white.. Grounded or un-grounded. In reality, its not yes or no... Its all a gradient.
My answer is ufta.. or was that Ufer?
Good info...
I'm looking at how hooking my my low impedance Ufer grounded garage interacts with the 25 ohm ground rod on my house. My take is that current is flowing to the UFER ground on the garage.
Basically an unintended ground path out to the garage.
My answer is ufta.. or was that Ufer?
Good info...
I'm looking at how hooking my my low impedance Ufer grounded garage interacts with the 25 ohm ground rod on my house. My take is that current is flowing to the UFER ground on the garage.
Basically an unintended ground path out to the garage.
25 Ohm? Did you have someone with the correct testing equipment & just as important, the knowledge to use it correctly do testing?
If you drive a ground rod as a grounding electrode, you have to prove 25 Ohms of resistance or less (expensive testing equipment) or just drive a 2nd rod at least 6' away & be done with it.
theoldwizard1
Well-known member
Back 10-25 years ago, I installed a fair amount of computer equipment. Back then computer equipment used a lot more power than today's server racks. Much of this was high power 20-30A single phase and 3 phase. ALL branch circuit were isolated ground.
roblouvasz
Well-known member
So is this guy saying that ground rods are not needed? Then why have three prong grounded outlets? If I have what this guy is saying correct, then if I have a piece of equipment that's running say an air compressor, and there's a short in the motor where as 120v is touching the the motor casing which is grounded, that voltage is going to my ground rod outside the shop. so if I walk near the ground rod i get electrocuted?
\
Electricity is not trying to go to ground, it is trying to return to it's source,which is the transformer, & it will take any and all paths which the earth is one path, if one were to rely on a ground rod to clear a fault it's doubtful the fault would clear, more likely somebody will be electrocuted.
wrench409
Well-known member
I found this video very informative.
Thanks for posting it!
Thanks for posting it!
hidollartoys
Well-known member
You are confusing "system ground" and equipment ground". The presentation is a little difficult to follow if you do not have a real good understanding of the concepts and theory. Mike Holt is considered an expert but sometimes will gloss over some aspects assuming the listener/reader already has a good knowledge of the subject.
Teken
Well-known member
This subject was touched upon by Mike last year as well. One of the problems in this video and that of the presenter is the endless conflict of the message.
When he spoke about Generac stating ground rods should be used for all (older) installs. Before he advised Generac that doing so would cause more damage etc.
This does NOT help anyone who did it the old way . . .
Not only is this double talk, it in no way helps anyone who has made this mistake. What should have been stated, and remedied is that the company (in this case Generac) should have sent out an immediate warning / clarification that grounding of the generator should NOT be done.
Due to new information, knowledge, testing, etc.
With respect to the solar array not being grounded. People are going to be hard pressed to change that. There isn't a POCO, Insurance Company, Electrician, or Inspector that will allow a grid tied solar array NOT grounded to Earth ground.
None . . .
So all the theory right or wrong doesn't change what happens in the real world.
Teken . . .
When he spoke about Generac stating ground rods should be used for all (older) installs. Before he advised Generac that doing so would cause more damage etc.
This does NOT help anyone who did it the old way . . .
Not only is this double talk, it in no way helps anyone who has made this mistake. What should have been stated, and remedied is that the company (in this case Generac) should have sent out an immediate warning / clarification that grounding of the generator should NOT be done.
Due to new information, knowledge, testing, etc.
With respect to the solar array not being grounded. People are going to be hard pressed to change that. There isn't a POCO, Insurance Company, Electrician, or Inspector that will allow a grid tied solar array NOT grounded to Earth ground.
None . . .
So all the theory right or wrong doesn't change what happens in the real world.
Teken . . .
theoldwizard1
Well-known member
It is interesting that almost no home small appliances have a ground connection. Same is true with hand held power tools.
The except desktop computers.
The except desktop computers.
Speedy Petey
Well-known member
This is not even remotely what the guy is saying. In fact he is saying the opposite.
The ground pin on the plug on your compressor has almost nothing to do with a rod stuck in the dirt outside.
ishiboo
Well-known member
Speedy Petey
Well-known member
PERFECT quote.
Stuart in MN
Well-known member
I don't think Mike Holt was talking about no ground connection at all, he was talking about a separate ground connection...his graphic marked as 'wrong' showed the solar array connected to a ground rod but it was separate and not connected back to the main ground.
Teken
Well-known member
I hope you realize a (separate) chassis ground is always used in a grid tied solar array. It is not tied to the main ground, right or wrong.
Remember, in his illustration it is assumed that the lightning struck the ground and went up. He does not address the point that if the solar array on your roof got struck by lightning at the panels, that a chassis / component ground would divert that energy to the ground.
This is why everyone is all over the map. People can baffle you with bull ****, or back it up with 999999999999999 pages of test, charts, graphs.
What is a person to do?
Teken . . .
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This ^^^^
The array should be bonded to the main ground and not use a second ground rod, and if you do use a second ground rod it needs to be bonded to the main rod.
Teken
Well-known member
All of us (who don't matter) agree. But, in the real world this is not done this way. The Generac example of what Mike Holt discussed was a perfect example of such.
The reality is depending upon where you're in the world and what the code is for that region, and the product you bought (new, old) this dictates what is done at the site.
My comments are based on observed installs and interactions with the POCO, electrician, and inspector. Its easy to say I saw this video on You Tube with Mike Holt or who ever person you believe lends credence to your cause.
At the end of the day the guy who signs off the permit has final say. Arguing over what should be done, opposed to how its done is fight you won't win and will result in a permit fail.
Teken . . .
ishiboo
Well-known member
Chassis grounds are tied to the "main ground", it's an EGC. Same with a roof-top AC unit's metal chassis or anything else. This is REQUIRED by the NEC and NOT OPTIONAL. As he said 10 times you cannot avoid grounding according to the NEC because the manual says you should, but you can add an additional ground rod tied to the EGC IF it requires it as that is not prohibited.
Remember - this is a video targeted towards electrical professionals, and it is their responsibility to install things according to manufacturer specs no matter right or wrong - the underlying message to that is, even if a generator or panel calls for a separate ground rod, it's not the best option. So if you're a homeowner it's better to do things right than according to the manual
He does address that, by saying you do not protect something from lightning by making it a part of the lightning protection, you protect around them. What this means is if you plan on protecting the panels from lightning, do so by placing lightning protection around the panels... not turning them into lightning rods themselves by making them the easiest path to ground.
If a solar array is directly struck by lightning, having the chassis grounded is very likely not going to save things. If a short in the inverter, or a lag bolt from the panels hit a live wire, or whatever energizes the panel chassis... that equipment ground being connected at the main panel will chances are clear the fault.
My guess is given houses typical proximities to trees, power poles, etc... the vast majority of household lightning damage is NOT from direct strikes. We had a lightning storm and lost a bunch of stuff as did several neighbors, and it was not a direct hit and randomly targeted things as lightning tends to do.
I think this video did a pretty good job of summing things up. The NEC, Mike Holt, etc. are all on the same page. If you're a homeowner do things correctly - if you're an electrical contractor, you're limited by what the equipment's installation information requires unless it's specifically addressed by the manufacturer.
Teken
Well-known member
Chassis grounds are tied to the "main ground", it's an EGC. Same with a roof-top AC unit's metal chassis or anything else. This is REQUIRED by the NEC and NOT OPTIONAL. As he said 10 times you cannot avoid grounding according to the NEC because the manual says you should, but you can add an additional ground rod tied to the EGC IF it requires it as that is not prohibited.
Remember - this is a video targeted towards electrical professionals, and it is their responsibility to install things according to manufacturer specs no matter right or wrong - the underlying message to that is, even if a generator or panel calls for a separate ground rod, it's not the best option. So if you're a homeowner it's better to do things right than according to the manual
He does address that, by saying you do not protect something from lightning by making it a part of the lightning protection, you protect around them. What this means is if you plan on protecting the panels from lightning, do so by placing lightning protection around the panels... not turning them into lightning rods themselves by making them the easiest path to ground.
If a solar array is directly struck by lightning, having the chassis grounded is very likely not going to save things. If a short in the inverter, or a lag bolt from the panels hit a live wire, or whatever energizes the panel chassis... that equipment ground being connected at the main panel will chances are clear the fault.
My guess is given houses typical proximities to trees, power poles, etc... the vast majority of household lightning damage is NOT from direct strikes. We had a lightning storm and lost a bunch of stuff as did several neighbors, and it was not a direct hit and randomly targeted things as lightning tends to do.
I think this video did a pretty good job of summing things up. The NEC, Mike Holt, etc. are all on the same page. If you're a homeowner do things correctly - if you're an electrical contractor, you're limited by what the equipment's installation information requires unless it's specifically addressed by the manufacturer.
You realize your entire reply made my point.
If I was some Joe Smoe and didn't have anyone to look over or care about my install. I could very well follow everything Mike Holt advised.But, if I am following the NEC / CEC and the final say falls on the inspector. It doesn't matter what I say or think, I have to follow his orders.
Now, if you could show me one residential solar install on a roof that has some sort of barrier or form of surrounding protection I would love to see it.
I have never seen it.
The only thing I have seen are large transorbs or similar and we all know even that will not protect against a direct strike.
Now, respect to doing things according to the manual or not. You realize a manufacturer is fully entitled to deny any warranty claim should it be found you did not follow their installation instructions.
Again, it doesn't matter what I think or not. What does matter is who is going to OK the final inspection or the company that is going to warranty my gear when it blows.
Teken . . .
A power tool w/ double insulation is acceptable, assuming proper listing by a NRTL such as UL, FM, CSA us. (For the purposes of this post I am considering the US only.)
Xicaque
Well-known member
So to clarify...
My portable 10k watt generator does not need to be grounded? Correct?
My portable 10k watt generator does not need to be grounded? Correct?
Speedy Petey
Well-known member
To clarify even further, are you asking if it needs to be connected to a grounding electrode (ground rod)?
If so, the answer is no.
ishiboo
Well-known member
ForceFed70
Well-known member
The idea of the video is great. The execution of it is really poor.
Seems about 1/3 information, 1/3 rant, and 1/3 bragging/story telling. Could have been done so much better.
Lots of people saying that the grounding rod isn't very useful, but it's there for a reason. My understanding is that it's mostly used so that the POCO can ensure that it's neutral/return line is at the same potential as earth. Basically, every household serviced works together to offer a low resistance path to ground.
Seems about 1/3 information, 1/3 rant, and 1/3 bragging/story telling. Could have been done so much better.
Lots of people saying that the grounding rod isn't very useful, but it's there for a reason. My understanding is that it's mostly used so that the POCO can ensure that it's neutral/return line is at the same potential as earth. Basically, every household serviced works together to offer a low resistance path to ground.
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ishiboo
Well-known member
It's part of a larger series/panel, it probably made more sense in that context.
I'm not sure anyone said a grounding rod wasn't useful. The point was they're NOT useful and perhaps detrimental in a lot of additional applications.
The purpose of the ground rods are to dissipate lightning/static charges/etc. Didn't you learn anything?
ForceFed70
Well-known member
It's part of a larger series/panel, it probably made more sense in that context.
I'm not sure anyone said a grounding rod wasn't useful. The point was they're NOT useful and perhaps detrimental in a lot of additional applications.
The purpose of the ground rods are to dissipate lightning/static charges/etc. Didn't you learn anything?
Lol. Have to admit that I stopped the video 1/2 way through as it was long and I hadn't learnt anything up until that point. Guess I should have stuck with it as I would have learnt something eventually. Thnx
Speedy Petey
Well-known member
This is (almost) completely wrong.
It's covered in the early part of that video.
Teken
Well-known member
And people often wonder why, when this subject comes up there are 9999999999 different replies or opinions?
Grounding is not magic, its the application of said ground and when it should be used that is critical. When all is said and done, in a residential home all paths lead to Earth Ground.
It doesn't matter if its a Ufer, Service Entrance, Water Pipe, or Electrical Panel. All of it is connected to the Earth.
Is there a difference between a chassis ground, circuit ground, and component ground?
Yes . . .
The part that is of contention is the addition of an additional grounding rod etc. As Mike illustrated in the light pole where they added a extra ground rod.
Some would argue this is wrong, while others (millions of others) all over North America are doing exactly what the photo shows.
Who is right? Who is wrong?
Is the average Joe going to argue with the installer, inspector, manufacturer?
Teken . . .
Grounding is not magic, its the application of said ground and when it should be used that is critical. When all is said and done, in a residential home all paths lead to Earth Ground.
It doesn't matter if its a Ufer, Service Entrance, Water Pipe, or Electrical Panel. All of it is connected to the Earth.
Is there a difference between a chassis ground, circuit ground, and component ground?
Yes . . .
The part that is of contention is the addition of an additional grounding rod etc. As Mike illustrated in the light pole where they added a extra ground rod.
Some would argue this is wrong, while others (millions of others) all over North America are doing exactly what the photo shows.
Who is right? Who is wrong?
Is the average Joe going to argue with the installer, inspector, manufacturer?
Teken . . .
That has happened before.
Why the shower? Please explain.
Let's say the copper feeds are not tied to the electrical ground. And you get a hot wire touching the copper feed. Now the feed is at 120v. Turn on the water in the shower and get in.
Fiberglass tub/surround; pvc drains. Where is the path to ground? How does the current pass through the body?
In an older house with iron tub and iron or copper drains the body would complete that circuit.
Engineer61
Well-known member
If you want to get a good understanding of grounding issues, look for the topic "ground loops" on digital design web sites or books. Mike mentions "electronics" several times and should say what he means by that instead of just giving the impression that it is things with circuit boards.
I would like this video MUCH better if Mike would say "separate grounds" instead of just "grounds". You want your equipment grounded, but only in one spot with only one wire to that spot. You don't want a generator to have a separate ground than the ground system in your house, doing so leads to the problems he is describing. You DO want your generator grounded, but with a nice big SINGLE wire that leads to the ground bond on your main panel; and if you can arrange it you want your generator insulated (rubber grommets in the cover mounting holes will work) from the concrete pad it sits on to prevent a separate ground connection from being formed. The same with the rest of the equipment he lists, you want it grounded through the main panel ground bond, NOT through a separate ground rod that would form an electrical loop with the main ground of your house. It's this ground loop, with your equipment in the middle of it that causes problems with lightning etc.
"More grounding" is not "better grounding"; "better grounding" is described as a single lower resistance path to ground. You want to drop that 25 ohm figure Mike keeps mentioning; and having separate ground rods distributed through your electrical system doesn't do that. Dropping a 20 foot section of 1" copper pipe alongside the foundation, then tying it to your main panel with insulated 0 gauge wire welded to the pipe instead of driving a six foot rod and using those bolt on clip connectors gives a better, i.e. lower resistance, ground; all of it buried deeply enough to eliminate the "step potential" problem that he also mentions.
I would like this video MUCH better if Mike would say "separate grounds" instead of just "grounds". You want your equipment grounded, but only in one spot with only one wire to that spot. You don't want a generator to have a separate ground than the ground system in your house, doing so leads to the problems he is describing. You DO want your generator grounded, but with a nice big SINGLE wire that leads to the ground bond on your main panel; and if you can arrange it you want your generator insulated (rubber grommets in the cover mounting holes will work) from the concrete pad it sits on to prevent a separate ground connection from being formed. The same with the rest of the equipment he lists, you want it grounded through the main panel ground bond, NOT through a separate ground rod that would form an electrical loop with the main ground of your house. It's this ground loop, with your equipment in the middle of it that causes problems with lightning etc.
"More grounding" is not "better grounding"; "better grounding" is described as a single lower resistance path to ground. You want to drop that 25 ohm figure Mike keeps mentioning; and having separate ground rods distributed through your electrical system doesn't do that. Dropping a 20 foot section of 1" copper pipe alongside the foundation, then tying it to your main panel with insulated 0 gauge wire welded to the pipe instead of driving a six foot rod and using those bolt on clip connectors gives a better, i.e. lower resistance, ground; all of it buried deeply enough to eliminate the "step potential" problem that he also mentions.
MrMark
Well-known member
You talking lightning? Because if you are talking a "better ground" for anything else I don't get it. Please explain the desirability of a "better ground" for other than lightning.
Speedy Petey
Well-known member
Well, again, much of this is wrong.
Ground loops are not an issue in AC building wiring. In electronics and sound systems withing the structure, yes, they can be an issue, but as far as the workings and safety of an ELECTRICAL system, NO.
Also, you DO NOT ground a generator to your electrical panel. This is not required or necessary. A separate ground rod for a standby genset WILL ABSOLUTELY NOT have ill effects on lighting etc.
In the same way that lowering the ohms on a grounding electrode system will have absolutely NO effect on the day to day workings of the systems. WHY do think we are told get to 25 ohms, OR two rods, and be done with it???
Not to sound rude, but you seem like the typical EE that thinks these type of things have any bearing on building wiring.
And you are crazy if you think ground rods eliminate step potential. This was specifically covered in the video.
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Speedy Petey
Well-known member
I'll reiterate, when you are having a problem with the electrical in your home, NOT electronics like AV or sound systems, and someone brings up "ground loops" please ignore that suggestion.
2ManyProjects
Well-known member
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- Jul 18, 2013
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They most certainly CAN BE.
And from where, exactly, do these "electronics and sound systems" get their power?
If there is an induced (or leaked) AC current on the neutral (or worse, EGC) due to a ground loop in the building's wiring, that can EASILY play hob with the operation of said "electronics and sound systems".
Not to sound rude, but you seem like the typical sparky who thinks ONLY in terms of building wiring (and perhaps secondarily about the safety issues specific to that very limited scope), with no regard to what is OPERATED off that building wiring.