Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 06-10-2012, 10:07 PM   #31
E2 Electrician
 
stickboy1375's Avatar
 
Join Date: Apr 2012
Location: Litchfield, CT
Posts: 4,723
Share |
Default

How does grounding work?


Quote:
Originally Posted by ddawg16 View Post
Your real good at quoting article 250(a)(1).....but I don't think you really understand what it means.....

westom's anology actually made quite a bit of sense......

May I suggest watching this video...it illustrates quite well what westcom was talking about.



The problem we are getting into now is trades vs engineers....

The trades know the rules and how to build to those rules....but in many cases, don't really understand the how and why of those 'rules'..

While engineers understand those rules...but sometimes strugle with how to physically implement those rules.

Case in point....my FIL can design a supersonic airplane....but would struggle to buck a single rivet in the plane.....

In a perfect world, there should never be any current flow to ground.

In a lightning strike....the voltage is typically imposed on all lines....including ground....the degree of which is determined by how close the hit and where exactly it is.

The since most of us are on 'the ground', it is preferable that any surges be directed to that potential.

As mentioned above...grounding is a long and distinguished subject.....that is still evolving....another case in point....the Ufer ground that is now code but yet was discovered in WWII.....and it took over 50 years to become a standard?

And the trades still argue about twist vs no twist....
Come on now... you know why trains are on tracks? so Engineers can drive them... all kidding aside, the info posted is useless to a DIYer... this topic can easily be explained in a few paragraphs... first off separating the difference between grounding electrodes, and EGC's... then its pretty basic after the two have been separated.


Last edited by stickboy1375; 06-10-2012 at 10:09 PM.
stickboy1375 is offline   Reply With Quote
Old 06-10-2012, 10:17 PM   #32
JOATMON
 
ddawg16's Avatar
 
Join Date: Aug 2011
Location: S. California
Posts: 6,853
Default

How does grounding work?


Quote:
Originally Posted by Cossack View Post
I am glad to see this discussion, but I am also having trouble understanding. Maybe explain what happens if there is no third ground wire as in older wiring. In old houses there is usually just a hot and neutral wire yet everything seems to work fine.
Good question....

Refereing to westcon's posts...if there was no connection between you and earth ground....you could grab either wire of the outlet....and not get shocked.....

But this is not a perfect world....

In many cases, there is some resistive path between you and earth ground. If you touch the hot wire...current will flow from it through you to ground.

The third wire was added so that earth ground could be taken to the device being powered. The assumption is that if there is an failure in insulation that would cause a short to something, it should happen in the device...hence, the ground wire in the device would be the low resistance path and not your body.

Recall seeing verbiage on electric tools that said "Double Insulated"?

Do you also remember power tools made of metal? In the old days, it was not uncommon for the wiring to short out inside and connect to the case....and then light up the user....

So...if you have a metal power tool...the earth ground is not connected to it's case...so the ground wire takes the juice and not your body.
__________________
"The dream is free but the hustle is sold separately."

My 2-Story Addition Build in Progress Link ... My Garage Build Link and My Jeep Build Link
ddawg16 is online now   Reply With Quote
Old 06-10-2012, 10:18 PM   #33
JOATMON
 
ddawg16's Avatar
 
Join Date: Aug 2011
Location: S. California
Posts: 6,853
Default

How does grounding work?


Quote:
Originally Posted by stickboy1375 View Post
Come on now... you know why trains are on tracks? so Engineers can drive them... all kidding aside, the info posted is useless to a DIYer... this topic can easily be explained in a few paragraphs... first off separating the difference between grounding electrodes, and EGC's... then its pretty basic after the two have been separated.
Can't argue that point....
__________________
"The dream is free but the hustle is sold separately."

My 2-Story Addition Build in Progress Link ... My Garage Build Link and My Jeep Build Link
ddawg16 is online now   Reply With Quote
The Following User Says Thank You to ddawg16 For This Useful Post:
stickboy1375 (06-10-2012)
Old 06-11-2012, 05:16 AM   #34
Member
 
Join Date: Nov 2011
Location: Md/Pa
Posts: 950
Default

How does grounding work?


Quote:
Originally Posted by stubie View Post
First thing is to understand that earth grounding has to do with equipment protection and consists of your GES (grounding electrode system) on the NEC side of the meter and the utility grounding on the NESC side of the meter (line side).
Good to see you Stubbie.

Is there any way for you to get your account back? It's a shame having to dump that huge post count and start all over again with a different name.
zappa is online now   Reply With Quote
Old 06-11-2012, 02:12 PM   #35
Member
 
Join Date: Jul 2006
Posts: 211
Default

How does grounding work?


So is having the new plastic boxes instead of metal a good thing since plastic does not have to be grounded?
Cossack is offline   Reply With Quote
Old 06-11-2012, 03:10 PM   #36
Licensed Electrical Cont.
 
Speedy Petey's Avatar
 
Join Date: Feb 2004
Location: NY State
Posts: 6,784
Default

How does grounding work?


Quote:
Originally Posted by Cossack View Post
So is having the new plastic boxes instead of metal a good thing since plastic does not have to be grounded?
"New"??
Where have you been? Plastic boxes have been around since the early 70's.

And yes, it is a bit easier since the ground does not have to hit the box, but only a bit easier.
__________________
Sometimes I feel like if I answer any more questions it is like someone trying to climb over a fence to jump off a bridge and me giving them a boost.
Answers based on the 2008 & 2011 NEC.
Speedy Petey is offline   Reply With Quote
Old 06-11-2012, 03:31 PM   #37
E2 Electrician
 
stickboy1375's Avatar
 
Join Date: Apr 2012
Location: Litchfield, CT
Posts: 4,723
Default

How does grounding work?


Quote:
Originally Posted by Cossack View Post
So is having the new plastic boxes instead of metal a good thing since plastic does not have to be grounded?
Id rather bond the box then the device, especially when a multi gang box is involved.
stickboy1375 is offline   Reply With Quote
Old 06-12-2012, 12:44 AM   #38
Member
 
Join Date: Oct 2010
Location: Central Indiana (USA)
Posts: 1,316
Default

How does grounding work?


In a nutshell, would the breaker trip without the ground rod being installed (assuming an EGC ran from the panel to each device/equipment)? I'm thinking yes, because I consider the rod to be "bonded" to the POCO ground via neutral.
sirsparksalot is offline   Reply With Quote
Old 06-12-2012, 01:05 AM   #39
Semi-Pro Electro-Geek
 
Join Date: Jul 2009
Location: Arizona, USA
Posts: 2,532
Default

How does grounding work?


Quote:
Originally Posted by sirsparksalot View Post
In a nutshell, would the breaker trip without the ground rod being installed (assuming an EGC ran from the panel to each device/equipment)? I'm thinking yes, because I consider the rod to be "bonded" to the POCO ground via neutral.
Yes. The grounding electrode (rod) has absolutely nothing to do with tripping breakers due to a fault. In fact, a ground rod will NOT trip a breaker due to a fault. You can connect a 120V hot wire to a ground rod and it will draw a few amps at most - definitely not enough to trip a 20A breaker. Bonding, not grounding, is responsible for clearing faults.
mpoulton is offline   Reply With Quote
The Following 3 Users Say Thank You to mpoulton For This Useful Post:
ddawg16 (06-12-2012), Speedy Petey (06-12-2012), stickboy1375 (06-12-2012)
Old 06-12-2012, 05:16 AM   #40
E2 Electrician
 
stickboy1375's Avatar
 
Join Date: Apr 2012
Location: Litchfield, CT
Posts: 4,723
Default

How does grounding work?


edited...

Last edited by stickboy1375; 06-12-2012 at 06:08 AM.
stickboy1375 is offline   Reply With Quote
Old 06-12-2012, 01:09 PM   #41
Member
 
Join Date: Oct 2010
Location: Central Indiana (USA)
Posts: 1,316
Default

How does grounding work?


Quote:
Originally Posted by sirsparksalot
In a nutshell, would the breaker trip without the ground rod being installed (assuming an EGC ran from the panel to each device/equipment)? I'm thinking yes, because I consider the rod to be "bonded" to the POCO ground via neutral.
Quote:
Originally Posted by mpoulton View Post
Yes. The grounding electrode (rod) has absolutely nothing to do with tripping breakers due to a fault. In fact, a ground rod will NOT trip a breaker due to a fault. You can connect a 120V hot wire to a ground rod and it will draw a few amps at most - definitely not enough to trip a 20A breaker. Bonding, not grounding, is responsible for clearing faults.
To continue then, can we say that the GE is there to bond the panel to the POCO xfrmr so that lightening strikes can be dissipated to ground through POCO's side?

In other words, the panel isn't bonded to the rod, rather, the POCO ground is bonded to the panel as a result of having it (the rod) connected to the neutral which goes back to the POCO's ground?

So, by providing a ground rod to the residence, we protect our equipment from damage by lightning strikes which are carried to earth via the neutral/ground bonding in the main panel? Ultimately, the rod is providing a path back to POCO's ground?
sirsparksalot is offline   Reply With Quote
Old 06-12-2012, 02:40 PM   #42
JOATMON
 
ddawg16's Avatar
 
Join Date: Aug 2011
Location: S. California
Posts: 6,853
Default

How does grounding work?


I came across this interesting writeup...special attention bold text

http://www.ece.ufl.edu/announcements...owerlines.html


Quote:

Lightning experts from the Electrical & Computer Engineering department are studying ways to reduce the cost of lightning damage by investigating how to repair and protect power lines that are hit by lightning. Lightning damage to power lines in the U.S. costs almost $1 billion annually, and 30 percent of all power outages are lightning related, according to studies by the Electric Power Research Institute (EPRI). The cost to industry of power failures led EPRI in 1993 to create the predecessor to what a year later became UF’s International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida.
“Industry wants power that stays steady at 60 cycles per second, with no impulses or failures caused by lightning,” says Martin Uman, UF Electrical & Computer Engineering (ECE) professor. “Power should be pure and uninterrupted,” says Uman, who, with ECE Professor Vladimir Rakov, is co-director of the ICLRT.
The ICLRT’s triggered lightning experiments involve underground and overhead power distribution lines built on the site. Presently, there are two different types of overhead lines that are identical to those used by power companies such as Florida Power & Light, which funds the present experiments.
Lightning is triggered by wire-trailing rockets fired toward overhead storm clouds. Lightning vaporizes the wires and follows their traces down in a manner that can be observed and studied. The researchers have investigated what happens when lightning hits power lines, how they fail, how to fix them, how to protect them, and equally important, the physics of that lightning.
A power line collects natural lightning that would otherwise strike in an alley about 100 feet wide on either side of the line. To protect against the effects of lightning strikes, power lines are often equipped with arresters and overhead ground wires. An arrester behaves like an open circuit when the line is in normal operation. When the line is hit by lightning, the arrester acts more like a short circuit. Like throwing a switch, it diverts lightning current to the ground, holds the voltage at safe value, and thereby keeps the line from harm.
The tests at the ICLRT revealed that up to half of all natural lightning strikes will cause the nearest arresters to fail, according to Uman.
The studies revealed that underground power lines are also vulnerable, contrary to previous beliefs, Rakov says. Ground lightning strikes affect underground distribution lines almost as often as they affect overhead lines. Further, the ground rods intended to dissipate the current actually act as interceptors. A percentage of the current does enter the system through the ground rods and can cause damage in the system.
As a further test, the ICLRT conducted an experiment on ground rods of the kind commonly used to protect homes from lightning. The observation that ground rods appeared to transmit the bulk of the current from lightning into the system rather than to “ground” was unexpected.
The researchers built a small structure with a typical lightning rod system at the ICLRT. Lightning rods placed on a home’s roof are supposed to route the current from a strike into the soil via wires connected to buried vertical ground rods. The established international standard for these systems allows no more than 50 percent of a lightning strike’s current to enter a home’s electrical system.
The experiment demonstrated that more than 80 percent of current from a lightning strike flowed into an electrical system when the ground rods were in sandy soil of the kind found in the southeastern states. Sandy soil tends to remain dry beneath the surface and therefore does not conduct electricity well.
Rakov says more research needs to be done to determine how lightning current is distributed through a system. The ICLRT studies have shown that in 50 percent of lightning strikes, the strong initial pulse of the current is followed by a tail of continuing current of variable duration. It is not now known how the continuing currents divide or if they flow through arresters. This is important because arresters are designed for and tested against strong pulses only, Rakov says.
In the meantime, the studies indicate that homeowners should probably use surge protectors at the electric meter and in the home. Wire ring grounding systems are also desirable. These systems involve lightning rods connected to a buried wire loop that circles the house. Because the loops have more surface area than ground rods, they can better dissipate current into the ground.
As for power lines, the solution lies with the power companies, Uman says, given the available results of the experiments. It is theoretically possible to make power lines lightning proof if overhead ground wires are combined with line arresters of the proper power and energy rating. And although there are several types of new lightning elimination or dissipation devices now sold that are advertised as able to protect against lightning by diverting it away from the power lines, they have not been proven to work in that situation, he says.
__________________
"The dream is free but the hustle is sold separately."

My 2-Story Addition Build in Progress Link ... My Garage Build Link and My Jeep Build Link
ddawg16 is online now   Reply With Quote
Old 06-12-2012, 03:53 PM   #43
E2 Electrician
 
stickboy1375's Avatar
 
Join Date: Apr 2012
Location: Litchfield, CT
Posts: 4,723
Default

How does grounding work?


Quote:
Originally Posted by sirsparksalot View Post
To continue then, can we say that the GE is there to bond the panel to the POCO xfrmr so that lightening strikes can be dissipated to ground through POCO's side?
No, we install GE's to prevent surface arcing, this is very messy when it occurs... Look at it this way, an electrical system works perfectly fine without the earth involved in the equation... read below to fully understand why we install them.

Quote:
Originally Posted by sirsparksalot View Post
In other words, the panel isn't bonded to the rod, rather, the POCO ground is bonded to the panel as a result of having it (the rod) connected to the neutral which goes back to the POCO's ground?
250.4 (A)(1) Electrical System Grounding. Electrical systems that are grounded shall be connected to the earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.

(Don't ask me what the last sentence means, because I have no idea.)


Quote:
Originally Posted by sirsparksalot View Post
So, by providing a ground rod to the residence, we protect our equipment from damage by lightning strikes which are carried to earth via the neutral/ground bonding in the main panel? Ultimately, the rod is providing a path back to POCO's ground?

The first part I agree with, the item in bold is false.

Last edited by stickboy1375; 06-12-2012 at 03:55 PM.
stickboy1375 is offline   Reply With Quote
Old 06-12-2012, 04:20 PM   #44
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Default

How does grounding work?


Quote:
Originally Posted by stickboy1375 View Post
will stabilize the voltage to earth during normal operation.
This seems to assume the house is supplied by the secondary of a transformer.
If the secondary winding of a transformer has no connection to earth its voltage with respect to the earth is undefined and indeterminate and depends on the interwinding capacitance, but note that the line-to-line voltage is defined and known.

They want this voltage to earth to be defined, predictable and small.

Last edited by Yoyizit; 06-12-2012 at 04:23 PM.
Yoyizit is offline   Reply With Quote
Old 06-12-2012, 04:59 PM   #45
Member
 
Join Date: Aug 2009
Posts: 77
Default

How does grounding work?


Quote:
Originally Posted by sirsparksalot View Post
So, by providing a ground rod to the residence, we protect our equipment from damage by lightning strikes which ...
I was careful in all posts to limit that discussion to earth and safety ground - only for human safety. Most everything in those posts were layman level concept. Understood by anyone with basic high school science. Limited only to what is required to protect humans - not transistors. Limited to simple concepts such as resistance and wire thickness.


Surge and lightning protection involves concepts understood by any tech or engineer after his first semester class. Concepts that involve impedance and wire length. That address transistor safety; not human safety.

For example, if earth is only the POCo's transformer, then the building is unearthed. Due to excessive impedance (ie a wire longer than 10 feet), the ground is virtually non-existent.

Everything about safety ground and earth ground for human safety and code requirements was simple layman stuff. Most of it I had learned by the age of 14. Electrical concepts for surge protection mean understanding more including this simple example:
A 200 watt transmitter connects to a long wire antenna. Someone touches that antenna wire and feels zero volts. He touches that wire elsewhere and shocked by over 100 volts. Why 0 volts and 100 volts on the same wire? Basic electrical concepts that also explain why a POCo's transformer earth ground is so electrically different from the homeowner's earth ground.

Also explains why only meeting the National Electrical code says little useful for transistor protection. Article 250 does define earthing as also providing surge protection. But says nothing about the hows and whys. More basic concepts follow.

Each layer of surge protection only has one critically essential item. The single point ground. Many protection systems have no protectors. But must always have that earth ground. The only item always required for surge protection is earth ground (which is not a safety ground). Any protector that does not make a 'low impedance' connection to earth, of course, does not even claim to protect from typically destructive surges. It's not earthed.

Previous discussions were safety ground (ie receptacle) and earth ground. When moving on to surge protection, that earth ground is only a homeowner's 'secondary' protection layer. (Receptacle safety ground is completely irrelevant.)

Homeonwers are strongly encouraged to inspect their 'primary' surge protection layer. A picture demonstrates what to inspect:
http://www.tvtower.com/fpl.html

Whereas the previous discussion was about voltage potentials; surge protection is about current and where hundreds of thousands of joules (energy) are absorbed. Protection is always about where energy dissipates. Absorbed by a 'secondary' protection layer (homeowner's earth ground) and by a 'primary' protection layer (ie see pictures).

Also critically important are connections to earth ground. Excessive impedance and other factors that subvert surge protection include wire too long (ie 'more than 10 feet') to earth, sharp wire bends, splices, insufficient electrodes in poor conducting soil, ground wire bundled with other wires (ie safety ground inside Romex power cable), and metallic conduit.

This only introduces different parameters relevant to surge protection. The previous discussion was only about wire resistance, voltages, neutral and ground wires, and wire thickness. Earthing for protection involves wire impedance, currents, how dedicated ground wires are routed, wire length, and a critically important concept called single point earth ground.

The previous discussion was the easy part. The rules that apply to surge protection are easily learned by any layman. But are more numerous and not entirely obvious.

Again, why does an antenna have 0 volts and 100 volts on the same wire? A basic electrical concept that electricians need not understand – as long as they only install per code and not for transistor safety.

This is only about copper wire and dirt. The easy stuff.


Last edited by westom; 06-12-2012 at 05:17 PM.
westom is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
DIY Electrical work in New Jersey electures Electrical 42 12-19-2012 03:19 PM
cable line grounding amakarevic Electrical 56 05-15-2012 09:22 PM
Duct work in garage. flashme18 HVAC 1 11-08-2009 06:29 PM
Grounding from Junction Box too Main tlj Electrical 5 10-25-2009 12:48 AM
Anyone want to take a shot at why #6 to attach antenna ground to breaker? Piedmont Electrical 44 01-08-2008 04:11 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.