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#1
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Ground Rod For House ?
Hello:
Was just wondering about this a bit. Live in the Boston area, in a typical Colonial built about 30 yrs ago. Have the "standard" 220 V line coming into the house from the street line Appears to be 3 conductors, the 2 phases and the neutral. My question is that I keep reading about houses needing, and the NEC requiring, a ground (or grounding) rod right outside the house. Don't seem to have one. Is an actual ground rod required ? Where would it be ? If not, why not ? Thanks, Bob |
#2
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Ground Rod For House ?
Robert11 wrote:
Hello: Was just wondering about this a bit. Live in the Boston area, in a typical Colonial built about 30 yrs ago. Have the "standard" 220 V line coming into the house from the street line Appears to be 3 conductors, the 2 phases and the neutral. My question is that I keep reading about houses needing, and the NEC requiring, a ground (or grounding) rod right outside the house. Don't seem to have one. Is an actual ground rod required ? Where would it be ? If not, why not ? Thanks, Bob Not required 30 years ago. More than likely the water service line to the street is metallic and the electric service has been grounded to that. If so, it makes a much more effective ground than a driven ground rod. Jim |
#3
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Ground Rod For House ?
That earthing electrode has been required since 1990s.
Water pipe is no longer acceptable as an earth ground (not to be confused with other grounds such as the safety ground that centers inside mains break box). That dedicated earth ground adjacent to breaker box is a solution to numerous technical problems. That earth ground rod being minimal grounding. Some require more than just a single rod. All other incoming utilities (telephone, cable, satellite dish) must make a less than 20 foot connection to the same earthing - per code. In reality, you want each connection to be less than 10. Robert11 wrote: Was just wondering about this a bit. Live in the Boston area, in a typical Colonial built about 30 yrs ago. Have the "standard" 220 V line coming into the house from the street line Appears to be 3 conductors, the 2 phases and the neutral. My question is that I keep reading about houses needing, and the NEC requiring, a ground (or grounding) rod right outside the house. Don't seem to have one. Is an actual ground rod required ? Where would it be ? If not, why not ? Thanks, Bob |
#4
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Ground Rod For House ?
Robert11 wrote:
Was just wondering about this a bit. Live in the Boston area, in a typical Colonial built about 30 yrs ago. Have the "standard" 220 V line coming into the house from the street line Appears to be 3 conductors, the 2 phases and the neutral. My question is that I keep reading about houses needing, and the NEC requiring, a ground (or grounding) rod right outside the house. Don't seem to have one. Is an actual ground rod required ? Where would it be ? If not, why not ? Thanks, Bob w_tom wrote: That earthing electrode has been required since 1990s. Water pipe is no longer acceptable as an earth ground (not to be confused with other grounds such as the safety ground that centers inside mains break box). That dedicated earth ground adjacent to breaker box is a solution to numerous technical problems. That earth ground rod being minimal grounding. Some require more than just a single rod. All other incoming utilities (telephone, cable, satellite dish) must make a less than 20 foot connection to the same earthing - per code. In reality, you want each connection to be less than 10. W Tom You keep making that statement even though you've been corrected several times. It is a disservice to the DIY community to repeatedly say "Water pipe is no longer acceptable as an earth ground." The US National Electric Code (NEC) requires that any underground metal water pipe that is ten or more feet in length shall be used as a grounding electrode. I know that you will now try to muddy the water by bringing up the requirement for a supplemental electrode but the fact is that regardless of how many electrodes you have you must use the underground metal water pipe as a grounding electrode if it is available on the premise. You can argue all you want but until the Code Making Panel that is responsible for chapter 250 of the US NEC changes the code underground water piping must be used as a grounding electrode in any locality that has adopted the NEC as that localities code. -- Tom Horne "This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison |
#5
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Ground Rod For House ?
"Commodore Joe Redcloud©" wrote in message ... On Thu, 29 Dec 2005 19:49:52 GMT, "Tom Horne, Electrician" wrote: Tom Horne "This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison For those who don't know, Edison's first working municipal electrical system was DC. Commodore Joe Redcloud© That's exactly why he said ac was dangerous. He had a vested interest in the use of DC. Bob |
#6
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Ground Rod For House ?
Robertm wrote: "Commodore Joe Redcloud©" wrote in message ... On Thu, 29 Dec 2005 19:49:52 GMT, "Tom Horne, Electrician" wrote: Tom Horne "This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison For those who don't know, Edison's first working municipal electrical system was DC. Commodore Joe Redcloud© That's exactly why he said ac was dangerous. He had a vested interest in the use of DC. Bob Which he actually developed into the electric chair: http://inventors.about.com/od/hstart...tric_Chair.htm 'Course DC is no fun either, talk to the guys who work on the CTAs "L" trains. They told me about pulling an arc in a light socket replacing a bulb, nothing to do but walk away from it. Richard |
#7
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Ground Rod For House ?
On Thu, 29 Dec 2005 14:09:20 -0600, "Robertm"
wrote: "Commodore Joe Redcloud©" wrote in message .. . On Thu, 29 Dec 2005 19:49:52 GMT, "Tom Horne, Electrician" wrote: Tom Horne "This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison For those who don't know, Edison's first working municipal electrical system was DC. Commodore Joe Redcloud© That's exactly why he said ac was dangerous. He had a vested interest in the use of DC. Bob And, considering what he wanted AC to be used for, "Westinghouse" was once a synonym for "electrocute". -- Mark Lloyd http://notstupid.laughingsquid.com "Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well armed lamb contesting the vote." - Benjamin Franklin |
#8
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Ground Rod For House ?
You have it backwards, Tom. Previously you made that
claim. Others then noted why you were wrong. Even if a home is earthed by a water pipe, that water pipe is no longer sufficient for earthing (exception is legacy conditions). The code requires bonding to water pipe - grounding for human safety. The code is quite specific as to what is required for an earthing electrode. I don't expect to change Tom Horne's opinion - having previously quoted code. But for the benefit of others, the code says in Article 250.53(D)(2): Supplemntal Electrode Required. A metal underground water pipe shall be supplemented by an additional electrode of a type specified in 250.52(A)(2) through (A)(7). Those six electrodes are 2) Metal Grame of the Building or Structure, 3) Concrete Encased Electrode (also called Ufer grounds), 4) Ground Ring (also called Halo ground), 5) Rod and pipe Electrodes (also called a copper clad ground rod), 6) Plate Electrodes, or 7) Other Local Metal Underground Systems or Structures. If earthed only to a water pipe, then a building does not have sufficient earthing. If no water pipe exists, any of the above ground electrodes 2 through 7 are sufficient - need not be supplemented. The water pipe is no longer sufficient for earth ground which is why it must be "supplemented". The Original Poster is advised to install earthing as required by post 1990 code. This for two reasons - human safety (per code) and transistor safety (which code does not address). Building's occupants also want transistor safety. Therefore a second reason why water pipe earthing is often insufficient as an earth ground. The code says water pipe earthing (which was standard before 19909) is insufficient. Appliance protection also demands an adjacent earthing electrode for other reasons electrical. Two reasons why water pipe earthing is no longer sufficient. NEC requires water pipe be bonded to AC electric safety ground - for human safety reasons. NEC requires other electrodes (2 through 7) for earthing. Robert11: volts500 also posted a description of other safety grounds in a post entitled "Grounding Rod Info" in the newsgroup alt.home.repair on 12 July 2003 at http://tinyurl.com/hkjq "Tom Horne, Electrician" wrote: W Tom You keep making that statement even though you've been corrected several times. It is a disservice to the DIY community to repeatedly say "Water pipe is no longer acceptable as an earth ground." The US National Electric Code (NEC) requires that any underground metal water pipe that is ten or more feet in length shall be used as a grounding electrode. I know that you will now try to muddy the water by bringing up the requirement for a supplemental electrode but the fact is that regardless of how many electrodes you have you must use the underground metal water pipe as a grounding electrode if it is available on the premise. You can argue all you want but until the Code Making Panel that is responsible for chapter 250 of the US NEC changes the code underground water piping must be used as a grounding electrode in any locality that has adopted the NEC as that localities code. |
#9
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Ground Rod For House ?
On 29 Dec 2005 12:33:59 -0800, "spudnuty" wrote:
Robertm wrote: "Commodore Joe Redcloud©" wrote in message ... On Thu, 29 Dec 2005 19:49:52 GMT, "Tom Horne, Electrician" wrote: Tom Horne "This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison For those who don't know, Edison's first working municipal electrical system was DC. Commodore Joe Redcloud© That's exactly why he said ac was dangerous. He had a vested interest in the use of DC. Bob Which he actually developed into the electric chair: Which is why his opponents, the competing company, were able to say that DC was dangerous, http://inventors.about.com/od/hstart...tric_Chair.htm 'Course DC is no fun either, talk to the guys who work on the CTAs "L" trains. That's where the metaphor got started, that abortion or social security or whatever is the "third rail" of American politics. The third rail, touch it and you die, referring to the power rail on an L: or subway. They told me about pulling an arc in a light socket replacing a bulb, nothing to do but walk away from it. Richard There's a bronze plaque in Lower Manhattan, NYC, where Edison's original power station was, but no museum or anything. Not worth going out of one's way for, unless you're really devoted to "being there". But there are other things to sightsee there, and the location would be in history books (but probably not in NYC tourist books.) (It's 2 to 4 blocks from the East River, and tthat might have been waterfront property at the time.) Remove NOPSAM to email me. Please let me know if you have posted also. |
#10
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Ground Rod For House ?
"Tom Horne, Electrician" wrote: W Tom You keep making that statement even though you've been corrected several times. It is a disservice to the DIY community to repeatedly say "Water pipe is no longer acceptable as an earth ground." The US National Electric Code (NEC) requires that any underground metal water pipe that is ten or more feet in length shall be used as a grounding electrode. I know that you will now try to muddy the water by bringing up the requirement for a supplemental electrode but the fact is that regardless of how many electrodes you have you must use the underground metal water pipe as a grounding electrode if it is available on the premise. You can argue all you want but until the Code Making Panel that is responsible for chapter 250 of the US NEC changes the code underground water piping must be used as a grounding electrode in any locality that has adopted the NEC as that localities code. w_tom wrote: You have it backwards, Tom. Previously you made that claim. Others then noted why you were wrong. Even if a home is earthed by a water pipe, that water pipe is no longer sufficient for earthing (exception is legacy conditions). The code requires bonding to water pipe - grounding for human safety. The code is quite specific as to what is required for an earthing electrode. I don't expect to change Tom Horne's opinion - having previously quoted code. But for the benefit of others, the code says in Article 250.53(D)(2): Supplemntal Electrode Required. A metal underground water pipe shall be supplemented by an additional electrode of a type specified in 250.52(A)(2) through (A)(7). Those six electrodes are 2) Metal Frame of the Building or Structure, 3) Concrete Encased Electrode (also called Ufer grounds), 4) Ground Ring (also called Halo ground), 5) Rod and pipe Electrodes (also called a copper clad ground rod), 6) Plate Electrodes, or 7) Other Local Metal Underground Systems or Structures. If earthed only to a water pipe, then a building does not have sufficient earthing. If no water pipe exists, any of the above ground electrodes 2 through 7 are sufficient - need not be supplemented. The water pipe is no longer sufficient for earth ground which is why it must be "supplemented". The Original Poster is advised to install earthing as required by post 1990 code. This for two reasons - human safety (per code) and transistor safety (which code does not address). Building's occupants also want transistor safety. Therefore a second reason why water pipe earthing is often insufficient as an earth ground. The code says water pipe earthing (which was standard before 19909) is insufficient. Appliance protection also demands an adjacent earthing electrode for other reasons electrical. Two reasons why water pipe earthing is no longer sufficient. NEC requires water pipe be bonded to AC electric safety ground - for human safety reasons. NEC requires other electrodes (2 through 7) for earthing. Robert11: volts500 also posted a description of other safety grounds in a post entitled "Grounding Rod Info" in the newsgroup alt.home.repair on 12 July 2003 at http://tinyurl.com/hkjq Quoting only part of the applicable section of the code does you no credit. I know what your opinion is as do most of the long time contributers here. What I'm talking about is what the US National Electric Code requires. While it is true that the code requires interior metal water piping to be bonded to the neutral of the service it also requires that any underground metal water piping that is ten or more feet in length be used as a grounding electrode. The reason that the NEC requires a supplemental grounding electrode is stated in the handbook thusly. The portion in brackets & italics is the handbook commentary. [The requirement to supplement the metal water pipe is based on the practice of using a plastic pipe for replacement when the original metal water pipe fails. This type of replacement leaves the system without a grounding electrode unless a supplementary electrode is provided.] In other words a driven rod electrode is better than nothing. Thus it is the risk of later replacement with plastic piping that is the reason for requiring that the underground metal water piping be supplemented with another type of grounding electrode. By actual measurement the underground metal water piping system provides a far lower resistance to earth than eight or ten foot driven rods. [Section 250.50 introduces the important concept of a “grounding electrode system,” in which all electrodes are bonded together, as illustrated in Exhibit 250.21. Rather than relying totally on a single electrode to perform its function over the life of the electrical installation, the NEC encourages the formation of a system of electrodes “if available on the premises.” There is no doubt that building a system of electrodes adds a level of reliability and helps ensure system performance over a long period of time.] 250.50 Grounding Electrode System. If available on the premises at each building or structure served, each item in 250.52(A)(1) through (A)(6) shall be bonded together to form the grounding electrode system. Where none of these electrodes are available, one or more of the electrodes specified in 250.52(A)(4) through (A)(7) shall be installed and used. 250.52 Grounding Electrodes. (A) Electrodes Permitted for Grounding. (1) Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more (including any metal well casing effectively bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductors. Interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall not be used as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system. Exception: In industrial and commercial buildings or structures where conditions of maintenance and supervision ensure that only qualified persons service the installation, interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall be permitted as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system, provided that the entire length, other than short sections passing perpendicular through walls, floors, or ceilings, of the interior metal water pipe that is being used for the conductor is exposed. (2) Metal Frame of the Building or Structure. The metal frame of the building or structure, where effectively grounded. (3) Concrete-Encased Electrode. An electrode encased by at least 50 mm (2 in.) of concrete, located within and near the bottom of a concrete foundation or footing that is in direct contact with the earth, consisting of at least 6.0 m (20 ft) of one or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than 13 mm (½ in.) in diameter, or consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 4 AWG. Reinforcing bars shall be permitted to be bonded together by the usual steel tie wires or other effective means. (4) Ground Ring. A ground ring encircling the building or structure, in direct contact with the earth, consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 2 AWG. (5) Rod and Pipe Electrodes. Rod and pipe electrodes shall not be less than 2.5 m (8 ft) in length and shall consist of the following materials. (a) Electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size 3/4) and, where of iron or steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection. (b) Electrodes of rods of iron or steel shall be at least 15.87 mm (5/8 in.) in diameter. Stainless steel rods less than 16 mm (5/8 in.) in diameter, nonferrous rods, or their equivalent shall be listed and shall not be less than 13 mm (1/2 in.) in diameter. (6) Plate Electrodes. Each plate electrode shall expose not less than 0.186 m2 (2 ft2) of surface to exterior soil. Electrodes of iron or steel plates shall be at least 6.4 mm (1/4 in.) in thickness. Electrodes of nonferrous metal shall be at least 1.5 mm (0.06 in.) in thickness. (7) Other Local Metal Underground Systems or Structures. Other local metal underground systems or structures such as piping systems and underground tanks. (B) Electrodes Not Permitted for Grounding. The following shall not be used as grounding electrodes: (1) Metal underground gas piping system (2) Aluminum electrodes -- Tom Horne Well we aren't no thin blue heroes and yet we aren't no blackguards to. We're just working men and woman most remarkable like you. |
#11
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Ground Rod For House ?
"Thomas D. Horne, FF EMT
Dec 30, 2:46 am show options Quoting only part of the applicable section of the code does you no credit. I know what your opinion is as do most of the long time contributers here. What I'm talking about is what the US National Electric Code requires. While it is true that the code requires interior metal water piping to be bonded to the neutral of the service it also requires that any underground metal water piping that is ten or more feet in length be used as a grounding electrode. The reason that the NEC requires a supplemental grounding electrode is stated in the handbook thusly. The portion in brackets & italics is the handbook commentary. [The requirement to supplement the metal water pipe is based on the practice of using a plastic pipe for replacement when the original metal water pipe fails. This type of replacement leaves the system without a grounding electrode unless a supplementary electrode is provided" Excellent job Thomas! This is exactly what I thought the reason was behind requiring a supplemental ground in addition to a water pipe ground. And I agree, that W Tom completely misrepresents this. His statements lead one to believe that there is something wrong from an electrical and lightning protection standpoint with using a water pipe ground. It's cear from the NEC that this is simply not true and the real reason is concern over a metal water pipe later being replaced by plastic, therby leaving the premise with no ground. |
#12
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Ground Rod For House ?
What you have described as a “grounding electrode system” is
the classic single point earth ground proven even in the 1930s to 'harden' high reliability facilities from electronics damage. Yes, separate earth grounds must be interconnected also for human safety reasons. But that is completely irrelevant to the original poster's question, is completely irrelevant to what I have posted, AND is what we want when earthing for transistor safety. So what is your point? Your definition of a 'grounding electrode system' does not contradict anything previously posted. Why are you questioning that a water pipe earthing alone is not sufficient when NEC says otherwise? Why are you adding irrelevant information about interconnected earth grounds? Information that is also irrelevant to the original poster's question? Nothing I posted here or in years previous said that buried water pipes cannot also be earthing electrodes. So why do you post as if I said just that? Meanwhile another reason for supplemental grounding (besides plastic pipe) is plumber protection. Plumber doing work on HIS pipes should not be concerned about electrical hazards. Supplemental earthing means a plumber does not, if disconnecting pipes, create an electrical hazard. Another reason why a water pipe earth ground is typically not sufficient is also something beyond NEC agenda: transistor protection. Water pipe alone is no longer sufficient for earthing. Nothing posted by Tom Horne supports his contrarian claims. Other earth grounds (2) through (7) by themselves are sufficient for earthing - do not require supplemental earthing. But a water pipe as the building's only earth ground is no longer sufficient; for numerous reasons. Robert11's original question was: ... about houses needing, and the NEC requiring, a ground (or grounding) rod right outside the house. Correct. The cold water pipe as earth ground is no longer sufficient. An earthing electrode dedicated only to a building's electrical system is also required. AND this ground must also connect, a short distance, to all incoming utilities. Now Tom. If I had said that cold water pipe cannot or need not be connected to building's ground system, then your last post would have merit. But that is not what I said - ever. 1) I said that cold water pipe must be bonded to a building's safety ground system. 2) I said that cold water pipe alone is no longer sufficient as a building's only earth ground. What you have quoted from the NEC does not dispute either point. 3) What I also posted describes earthing for essential functions beyond what code calls for. Again, nothing you have posted disputes that either. So why do you post what is also irrelevant to the OP's original question? "Thomas D. Horne, FF EMT" wrote: Quoting only part of the applicable section of the code does you no credit. I know what your opinion is as do most of the long time contributers here. What I'm talking about is what the US National Electric Code requires. While it is true that the code requires interior metal water piping to be bonded to the neutral of the service it also requires that any underground metal water piping that is ten or more feet in length be used as a grounding electrode. The reason that the NEC requires a supplemental grounding electrode is stated in the handbook thusly. The portion in brackets & italics is the handbook commentary. [The requirement to supplement the metal water pipe is based on the practice of using a plastic pipe for replacement when the original metal water pipe fails. This type of replacement leaves the system without a grounding electrode unless a supplementary electrode is provided.] In other words a driven rod electrode is better than nothing. Thus it is the risk of later replacement with plastic piping that is the reason for requiring that the underground metal water piping be supplemented with another type of grounding electrode. By actual measurement the underground metal water piping system provides a far lower resistance to earth than eight or ten foot driven rods. [Section 250.50 introduces the important concept of a “grounding electrode system,” in which all electrodes are bonded together, as illustrated in Exhibit 250.21. Rather than relying totally on a single electrode to perform its function over the life of the electrical installation, the NEC encourages the formation of a system of electrodes “if available on the premises.” There is no doubt that building a system of electrodes adds a level of reliability and helps ensure system performance over a long period of time.] 250.50 Grounding Electrode System. If available on the premises at each building or structure served, each item in 250.52(A)(1) through (A)(6) shall be bonded together to form the grounding electrode system. Where none of these electrodes are available, one or more of the electrodes specified in 250.52(A)(4) through (A)(7) shall be installed and used. 250.52 Grounding Electrodes. (A) Electrodes Permitted for Grounding. (1) Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more (including any metal well casing effectively bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductors. Interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall not be used as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system. Exception: In industrial and commercial buildings or structures where conditions of maintenance and supervision ensure that only qualified persons service the installation, interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall be permitted as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system, provided that the entire length, other than short sections passing perpendicular through walls, floors, or ceilings, of the interior metal water pipe that is being used for the conductor is exposed. (2) Metal Frame of the Building or Structure. The metal frame of the building or structure, where effectively grounded. (3) Concrete-Encased Electrode. An electrode encased by at least 50 mm (2 in.) of concrete, located within and near the bottom of a concrete foundation or footing that is in direct contact with the earth, consisting of at least 6.0 m (20 ft) of one or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than 13 mm (½ in.) in diameter, or consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 4 AWG. Reinforcing bars shall be permitted to be bonded together by the usual steel tie wires or other effective means. (4) Ground Ring. A ground ring encircling the building or structure, in direct contact with the earth, consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 2 AWG. (5) Rod and Pipe Electrodes. Rod and pipe electrodes shall not be less than 2.5 m (8 ft) in length and shall consist of the following materials. (a) Electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size 3/4) and, where of iron or steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection. (b) Electrodes of rods of iron or steel shall be at least 15.87 mm (5/8 in.) in diameter. Stainless steel rods less than 16 mm (5/8 in.) in diameter, nonferrous rods, or their equivalent shall be listed and shall not be less than 13 mm (1/2 in.) in diameter. (6) Plate Electrodes. Each plate electrode shall expose not less than 0.186 m2 (2 ft2) of surface to exterior soil. Electrodes of iron or steel plates shall be at least 6.4 mm (1/4 in.) in thickness. Electrodes of nonferrous metal shall be at least 1.5 mm (0.06 in.) in thickness. (7) Other Local Metal Underground Systems or Structures. Other local metal underground systems or structures such as piping systems and underground tanks. (B) Electrodes Not Permitted for Grounding. The following shall not be used as grounding electrodes: (1) Metal underground gas piping system (2) Aluminum electrodes |
#13
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Ground Rod For House ?
To the OP: if you are going to post the same message to multiple
newsgroups use crossposting - that way multiple people don't have to answer the same question and we may see a wider range of answers. The answer to the original question, as stated by Speedy Jim, Tom and by others at alt.engineering.electrical is that a water pipe is normally the best easily obtained ground. As has been stated on both newsgroups, the only reason a ground rod is required, as supplemental electrode, is that water pipe may someday be replaced by plastic. For an existing house (that is, the OP) the NEC did not used to require a ground rod and does not require adding a ground rod unless replacing the service. Adding one will not improve the ground system unless the water pipe turns to plastic. A water pipe is one of 3 electrodes that must be connected, if present, as the ground system. A rod is a supplemental eletrode, not one of the 3. I have seen stated typical ground resistance values of 3 ohms for water pipe, also 0.1 ohm (remember this is usually an extensive network of metal below the frost line and likely nearer ground water than a rod). Ground rods are good, acording to the NEC, if their resistance is below 25 ohms. If not below then drive 2 rods and you don't have to measure - no reason it couldn't be above 25 ohms. Which do you think is a better ground? Why do you have to measure the ground resistance only with a rod? I agree entirely with fellow electrician Tom Horne. Incidentally the second best electrode for a house is likely a concrete encased electrode. It can be used alone (no rod) and can be used as the supplemental electrode for a water pipe. If I was building a house I would include one. They were studied for 18 years and over that period had a ground resistance of 2.1 to 4.8 ohms. w_tom wrote: What you have described as a “grounding electrode system” is the classic single point earth ground proven even in the 1930s to 'harden' high reliability facilities from electronics damage. Yes, separate earth grounds must be interconnected also for human safety reasons. But that is completely irrelevant to the original poster's question, is completely irrelevant to what I have posted, AND is what we want when earthing for transistor safety. So what is your point? Your definition of a 'grounding electrode system' does not contradict anything previously posted. Why are you questioning that a water pipe earthing alone is not sufficient when NEC says otherwise? Why are you adding irrelevant information about interconnected earth grounds? Information that is also irrelevant to the original poster's question? Nothing I posted here or in years previous said that buried water pipes cannot also be earthing electrodes. So why do you post as if I said just that? Meanwhile another reason for supplemental grounding (besides plastic pipe) is plumber protection. Plumber doing work on HIS pipes should not be concerned about electrical hazards. Supplemental earthing means a plumber does not, if disconnecting pipes, create an electrical hazard. Actually I thought plumbers were smart enough to handle this. The current code is that the connection has to be made within 5 feet of the entrance. Another reason why a water pipe earth ground is typically not sufficient is also something beyond NEC agenda: transistor protection. Never explained - why the lowest resistance isn't the best protection. Water pipe alone is no longer sufficient for earthing. Nothing posted by Tom Horne supports his contrarian claims. Other earth grounds (2) through (7) by themselves are sufficient for earthing - do not require supplemental earthing. But a water pipe as the building's only earth ground is no longer sufficient; for numerous reasons. Numerous reasons - never stated. Robert11's original question was: ... about houses needing, and the NEC requiring, a ground (or grounding) rod right outside the house. Correct. The cold water pipe as earth ground is no longer sufficient. An earthing electrode dedicated only to a building's electrical system is also required. AND this ground must also connect, a short distance, to all incoming utilities. Apparently there is a problem with an electrode also being a water pipe? What might that be? I agree protector blocks for cable and TV should be immediately adjacent to the panel so all wiring is clamped to the same ground reference. I would suggest that is likely more important than the grounding electrode. But then it would seem like the lowest resistance ground path would be best. Now Tom. If I had said that cold water pipe cannot or need not be connected to building's ground system, then your last post would have merit. But that is not what I said - ever. 1) I said that cold water pipe must be bonded to a building's safety ground system. 2) I said that cold water pipe alone is no longer sufficient as a building's only earth ground. What you have quoted from the NEC does not dispute either point. 3) What I also posted describes earthing for essential functions beyond what code calls for. Again, nothing you have posted disputes that either. So why do you post what is also irrelevant to the OP's original question? "Thomas D. Horne, FF EMT" wrote: Quoting only part of the applicable section of the code does you no credit. I know what your opinion is as do most of the long time contributers here. What I'm talking about is what the US National Electric Code requires. While it is true that the code requires interior metal water piping to be bonded to the neutral of the service it also requires that any underground metal water piping that is ten or more feet in length be used as a grounding electrode. The reason that the NEC requires a supplemental grounding electrode is stated in the handbook thusly. The portion in brackets & italics is the handbook commentary. [The requirement to supplement the metal water pipe is based on the practice of using a plastic pipe for replacement when the original metal water pipe fails. This type of replacement leaves the system without a grounding electrode unless a supplementary electrode is provided.] In other words a driven rod electrode is better than nothing. Thus it is the risk of later replacement with plastic piping that is the reason for requiring that the underground metal water piping be supplemented with another type of grounding electrode. By actual measurement the underground metal water piping system provides a far lower resistance to earth than eight or ten foot driven rods. [Section 250.50 introduces the important concept of a “grounding electrode system,” in which all electrodes are bonded together, as illustrated in Exhibit 250.21. Rather than relying totally on a single electrode to perform its function over the life of the electrical installation, the NEC encourages the formation of a system of electrodes “if available on the premises.” There is no doubt that building a system of electrodes adds a level of reliability and helps ensure system performance over a long period of time.] 250.50 Grounding Electrode System. If available on the premises at each building or structure served, each item in 250.52(A)(1) through (A)(6) shall be bonded together to form the grounding electrode system. Where none of these electrodes are available, one or more of the electrodes specified in 250.52(A)(4) through (A)(7) shall be installed and used. 250.52 Grounding Electrodes. (A) Electrodes Permitted for Grounding. (1) Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more (including any metal well casing effectively bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductors. Interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall not be used as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system. Exception: In industrial and commercial buildings or structures where conditions of maintenance and supervision ensure that only qualified persons service the installation, interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall be permitted as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system, provided that the entire length, other than short sections passing perpendicular through walls, floors, or ceilings, of the interior metal water pipe that is being used for the conductor is exposed. (2) Metal Frame of the Building or Structure. The metal frame of the building or structure, where effectively grounded. (3) Concrete-Encased Electrode. An electrode encased by at least 50 mm (2 in.) of concrete, located within and near the bottom of a concrete foundation or footing that is in direct contact with the earth, consisting of at least 6.0 m (20 ft) of one or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than 13 mm (½ in.) in diameter, or consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 4 AWG. Reinforcing bars shall be permitted to be bonded together by the usual steel tie wires or other effective means. (4) Ground Ring. A ground ring encircling the building or structure, in direct contact with the earth, consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 2 AWG. (5) Rod and Pipe Electrodes. Rod and pipe electrodes shall not be less than 2.5 m (8 ft) in length and shall consist of the following materials. (a) Electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size 3/4) and, where of iron or steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection. (b) Electrodes of rods of iron or steel shall be at least 15.87 mm (5/8 in.) in diameter. Stainless steel rods less than 16 mm (5/8 in.) in diameter, nonferrous rods, or their equivalent shall be listed and shall not be less than 13 mm (1/2 in.) in diameter. (6) Plate Electrodes. Each plate electrode shall expose not less than 0.186 m2 (2 ft2) of surface to exterior soil. Electrodes of iron or steel plates shall be at least 6.4 mm (1/4 in.) in thickness. Electrodes of nonferrous metal shall be at least 1.5 mm (0.06 in.) in thickness. (7) Other Local Metal Underground Systems or Structures. Other local metal underground systems or structures such as piping systems and underground tanks. (B) Electrodes Not Permitted for Grounding. The following shall not be used as grounding electrodes: (1) Metal underground gas piping system (2) Aluminum electrodes |
#14
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Ground Rod For House ?
"w_tom" wrote in message ... What you have described as a "grounding electrode system" is the classic single point earth ground proven even in the 1930s to 'harden' high reliability facilities from electronics damage. Yes, separate earth grounds must be interconnected also for human safety reasons. But that is completely irrelevant to the original poster's question, is completely irrelevant to what I have posted, AND is what we want when earthing for transistor safety. What is this "transistor safety" that you keep talking about? Please explain. |
#15
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Ground Rod For House ?
Water pipe makes a good low resistance ground. Human safety
demands a low resistance ground for reasons that include, for example, neutral wire failure. Transistor safety uses grounding components for a different purpose. Transistor safety requires a low impedance ground. If connecting a bonding wire to a water pipe 50 feet away, the house has a low resistance ground and a high impedance ground. High impedance means ineffective transistor protection. Take this fax machine protection as an example: http://www.epri-peac.com/tutorials/sol01tut.html Unfortunately AC electric and phone service enter on two sides of the house - bad construction practice. If 'pictured' water pipe is a significantly lower impedance connection, then a destructive transient will find the building's single point earth ground via NID (surge protector) and cold water pipe. But in reality, cold water pipes are typically too long, too many solder joints, too many sharp bends, etc. To connect to a common point, an additional wire that is not shown. All increase impedance so much that a transient will also seek a destructive path to earth via the fax machine. Incoming on phone line. Outgoing on AC electric wire. Fax machine damaged because NID was not earthing via a low impedance earth ground connection. This demonstrates but one example of how portable phone base stations, fax machines, and modems are so easily damaged. Essential to transistor protection is a connection from each incoming utility, either through a protector or by direct hardwire, to a common earth ground connection. Single point earthing most easily accomplished with a ground rod wired short (ie. less than 10 feet) to AC electric box. For transistor safety, all incoming utilities (telephone, cable TV, satellite disk) must make a less than 10 foot connection to this common earthing point. Another problem with using a cold water pipe as an earth ground connection - code wants each utility to be earthed less than 20 feet to the common point. Pipes (ie outside faucet) often are just too far - more than 20 feet - to the common earth ground point. Labeled 'arrestor' in that picture, same rules apply to that a 'whole house' protector. Arrestor must make a short connection to the single point earthing. 30 feet across the basement to where cold water pipe enters the building is all but no earth ground to that 'arrestor' - too much impedance. An earth ground rod adjacent to a breaker box is also for transistor safety - a low impedance earthing connection. A most common source of transistor destructive transients to things such as computer modems is incoming on AC electric. Wires highest on poles - AC electric - are more often struck; not lower cable and phone line. If that 'arrestor' does not connect AC electric wire to earth ground, then a transient (again in that picture) goes into fax machine (modem) on L connection, then destructively out on phone wires to NID and to earth ground. Above demonstrates why fax machines, modems, and portable phone bases stations are so often damaged by AC electric wire transients. Above is pre-WWII technology now made necessary in dwellings due to something new - transistors. Transistor protection is often little understood by some electricians who only understand NEC requirements. NEC does not require transistor protection. NEC is for human protection. Transistor protection is defined by the most critical component in a protection system: earth ground. Gfretwell has posted how homes are now being built so as to provide superior transistor safety in pictures at: http://members.aol.com/gfretwell/ufer.jpg Another also demonstrates better earthing. None of this would be required if city water pipe was sufficient as earth ground for transistor safety: http://www.knology.net/~res0958z/ Above was earthing for secondary protection. Also necessary is earthing for primary protection: http://www.tvtower.com/fpl.html Oscar_Lives wrote: "w_tom" wrote in message ... What you have described as a "grounding electrode system" is the classic single point earth ground proven even in the 1930s to 'harden' high reliability facilities from electronics damage. Yes, separate earth grounds must be interconnected also for human safety reasons. But that is completely irrelevant to the original poster's question, is completely irrelevant to what I have posted, AND is what we want when earthing for transistor safety. What is this "transistor safety" that you keep talking about? Please explain. |
#16
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Ground Rod For House ?
Its called 'legacy'. Changes per code required only if
changing or installing new wiring. Code does not require homeowner to upgrade earthing to unmodified installations. Code also does not address transistor safety. A short connection to a dedicated earth ground is installed also as part of a transistor safety 'system'. That detailed elsewhere. Bud-- does not even quote code to justify his post. Code now says water pipe ground is insufficient. Any other earthing electrode in that list (A)(2) through (A)(7) is sufficient for earthing. If using water pipe for earthing, then other earth grounds must also be installed because a water pipe ground is no longer sufficient per 250.52(D)(2). Code is quite clear. Water pipe is no longer sufficient for earthing as revised code specifically states. Bud-- does not quote code. Other reasons for a dedicated earth ground include plumber safety during a disconnected water pipe. Code also calls for a jumper wire across water meter for same reasons. Plumber should not be threatened by electrical hazards. Plumber safety - another reason why water pipe earth ground is not sufficient and must be supplemented. Water pipe must be bonded to AC electric for human safety reasons. The only electrical connection acceptable to pipes are connections that remove electricity. This for many reasons including future use of plastic pipe and plumber safety. No longer acceptable to wire electrical devices to water pipes with intent of making that water pipe a safety ground. Electric wire connections to water pipes are permitted only to remove dangerous electric currents from those pipes. Why does code also require a second earth ground rod if earth resistance is too high (25 ohms)? Second rod would not be necessary if water pipe was sufficient as an earth ground. But again, water pipe is no longer sufficient as an earth ground. Water pipe must be supplemented by something that is sufficient for earthing. Second copper clad rod may be required because an earth ground rod (or any other electrode from the list (A)(2) through (A)(7) ) is now the essential earthing electrode. It supplements making water pipe only a secondary and insufficient earth ground; as overtly stated in 250.53(D)(2) - quoted previously. Meanwhile, a homeowner wants this adjacent earth ground also for impedance reasons. Electricians rarely need understand impedance. Code only demands low resistance. But for electronics protection, a homeowner needs a low "impedance" earth ground, which a water pipe often does not provide. See a reply to Oscar_lives for details explaining transistor safety and impedance. Also see that post for an earthing pictures because water pipe ground is not sufficient. Bud-- wrote: To the OP: if you are going to post the same message to multiple newsgroups use crossposting - that way multiple people don't have to answer the same question and we may see a wider range of answers. The answer to the original question, as stated by Speedy Jim, Tom and by others at alt.engineering.electrical is that a water pipe is normally the best easily obtained ground. As has been stated on both newsgroups, the only reason a ground rod is required, as supplemental electrode, is that water pipe may someday be replaced by plastic. For an existing house (that is, the OP) the NEC did not used to require a ground rod and does not require adding a ground rod unless replacing the service. Adding one will not improve the ground system unless the water pipe turns to plastic. A water pipe is one of 3 electrodes that must be connected, if present, as the ground system. A rod is a supplemental eletrode, not one of the 3. I have seen stated typical ground resistance values of 3 ohms for water pipe, also 0.1 ohm (remember this is usually an extensive network of metal below the frost line and likely nearer ground water than a rod). Ground rods are good, acording to the NEC, if their resistance is below 25 ohms. If not below then drive 2 rods and you don't have to measure - no reason it couldn't be above 25 ohms. Which do you think is a better ground? Why do you have to measure the ground resistance only with a rod? I agree entirely with fellow electrician Tom Horne. Incidentally the second best electrode for a house is likely a concrete encased electrode. It can be used alone (no rod) and can be used as the supplemental electrode for a water pipe. If I was building a house I would include one. They were studied for 18 years and over that period had a ground resistance of 2.1 to 4.8 ohms. |
#17
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Ground Rod For House ?
w_tom wrote:
Water pipe makes a good low resistance ground. Human safety demands a low resistance ground for reasons that include, for example, neutral wire failure. Transistor safety uses grounding components for a different purpose. Transistor safety requires a low impedance ground. If connecting a bonding wire to a water pipe 50 feet away, the house has a low resistance ground and a high impedance ground. High impedance means ineffective transistor protection. Take this fax machine protection as an example: http://www.epri-peac.com/tutorials/sol01tut.html As I said protector blocks for cable and TV should be immediately adjacent to the panel so all wiring is clamped to the same ground reference. You don't explain how a ground rod would help in this instance. Adding a ground rod near the FAX is not going to provide a low impedance to keep the ground reference for the FAX the same as the incoming neutral. For transistor safety, all incoming utilities (telephone, cable TV, satellite disk) must make a less than 10 foot connection to this common earthing point. Incoming utilities listed have to have protector blocks near the power panel to get a common grounding reference. How does a 10 foot wire to a high resistance ground rod provide a lower ground impedance than a grounding electrode conductor and water pipe? This is cental to your arguments. Perhaps you could explain and also provide some citations that support your view. For a 500A service the conductor to a ground rod has to be #6. The conductor to a water pipe has to be 2/0 - 3.5 x the area. How come? Surges include high frequency components for which impedance is important. Grounding electrode conductor and water pipe has one function of limiting surges. Another problem with using a cold water pipe as an earth ground connection - code wants each utility to be earthed less than 20 feet to the common point. Cite the code. A most common source of transistor destructive transients to things such as computer modems is incoming on AC electric. Wires highest on poles - AC electric - are more often struck; not lower cable and phone line. If that 'arrestor' does not connect AC electric wire to earth ground, then a transient (again in that picture) goes into fax machine (modem) on L connection, then destructively out on phone wires to NID and to earth ground. Above demonstrates why fax machines, modems, and portable phone bases stations are so often damaged by AC electric wire transients. Clamping all incoming wires to the same the same ground reference is the best way I know to protect electronics. That requires the protector blocks to be near the electrical panel. (More properly thay have to be near each other.) That is likely a lot more important than resistance or impedance to ground. If all wiring was clamped to the same reference with no ground connection could electronics see a difference. Gfretwell has posted how homes are now being built so as to provide superior transistor safety in pictures at: http://members.aol.com/gfretwell/ufer.jpg This is a concrete encased electrode which I said is probably the second best electrode (after water pipes). It is one of 3 electrodes that must be included in a ground system, if present. (The other 2 are water pipe and building steel, which a home doesn't have.) Not included: ground rod. Another also demonstrates better earthing. None of this would be required if city water pipe was sufficient as earth ground for transistor safety: http://www.knology.net/~res0958z/ Most of us don't put 55 foot high lightning rods in our back yard. Not particualrly relevant. ------------- With regard to: Bud-- does not even quote code to justify his post. You do not understand why water pipes are required to have a SUPPLEMENTAL electrode and don't listen to people who do understand. Since arguing the code is pointles, I tried Physics - ground resistance. That doesn't seem to work either. bud-- |
#18
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Ground Rod For House ?
Mercy! I'm not quite sure what you're trying to say here, or
what the point of some of the irrelevant URLs/comments might be, but ... either you need to step back and put your heard around this again, or seek further education and experience. You'll probably object to my post here, but it's so typical of many on this group lately that I just can't hold it in any longer. Those who have nothing to say, should say exactly that. Those who do have something to say, should be clear and concise about it. Rationalization and guessing have no place in the realm of safety. "w_tom" wrote in message ... : Water pipe makes a good low resistance ground. Human safety : demands a low resistance ground for reasons that include, for : example, neutral wire failure. === Water pipe does not make a "low resistance" ground. It makes a "ground", period. The word "low" must have a contextual reference to be meaningful and there is none there. Besides, it's not resistive; it also contains a reactive component, sometimes surprisingly large. : : Transistor safety uses grounding components for a different : purpose. === What is "transistor safety"? That makes no sense. You apparently mean protection, as in protecting semi-conductor devices from overvoltages. Further, you will find nearly no transistors used anywhere these days in current designs. Semiconductor, yes; transistor type semiconductors; pretty scarce these days. .... Transistor safety requires a low impedance ground. === No, it requires a stable reference w/r to the rest of the ckt. : If connecting a bonding wire to a water pipe 50 feet away, the : house has a low resistance ground and a high impedance : ground. === Resistance or impedance? Are you using these interchangably? They are two entirely different things. Impedance would be the term you need here as the reactive components are substantial. High impedance means ineffective transistor : protection. === Now you've switched from safety to protection. Which is it? What high impedance are you talking about? Take this fax machine protection as an example: : http://www.epri-peac.com/tutorials/sol01tut.html : : Unfortunately AC electric and phone service enter on two : sides of the house - bad construction practice. === Bad assumption: that's a schematic representation, not a bad construction practice, and the only thing you can discern from it is the marked distances indicated for wiring. If 'pictured' : water pipe is a significantly lower impedance connection, then : a destructive transient will find the building's single point : earth ground via NID (surge protector) === NID is NOT a surge protector. NID is the Network Interface Device, and PART of it is surge suppression, NOT for any purpose other than protecting the demarcation point connections at a 600V clamping voltage. YOu've mis-assumed some things there. and cold water pipe. : But in reality, cold water pipes are typically too long, too : many solder joints, too many sharp bends, etc. === Sharp BENDS matter to resistance/impedance? I don't THINK so! What are you worried about, the kinetic energy of the moving electrons going around a corner where centifugal force slows them down? I hope not! You don't understand conductivity, I'm afraid. You're just parroting and trying to justify something with rationalization. It doesn't work. To connect to : a common point, an additional wire that is not shown. All : increase impedance so much that a transient will also seek a : destructive path to earth via the fax machine. === A "transient" will NOT seek a "destructive" path to earth. It will seek the path of least resistance to current flow whether that consist of pure resistance (it doesn't) or either of the reactive elements. Another way to state it is, it will seek any potential lower than itself in magnitude. That includes ac characteristics, by the way. Incoming on : phone line. Outgoing on AC electric wire. Fax machine : damaged because NID was not earthing via a low impedance earth : ground connection. === NO ELECTRONICS are protected, nor are they intended to be protected by, the telco surge suppression components, which are often arc-over devices or gas tubes or carbon stacks. : : This demonstrates but one example of how portable phone base : stations, fax machines, and modems are so easily damaged. === It does indeed, but it does so because there is no protection afforded to, nor intended to be afforded to, electronic equipment by the telco protectors. You've completely lost track of what a ground reference means in these contexts. Or, don't know what it means. : Essential to transistor protection is a connection from each : incoming utility, either through a protector or by direct : hardwire, to a common earth ground connection. Single point : earthing most easily accomplished with a ground rod wired : short (ie. less than 10 feet) to AC electric box. For : transistor safety, all incoming utilities (telephone, cable : TV, satellite disk) must make a less than 10 foot connection : to this common earthing point. === It's obvious you've been reading, but ... you're not putting things together correctly. : .... : A most common source of transistor destructive transients to : things such as computer modems is incoming on AC electric. : Wires highest on poles - AC electric - are more often struck; : not lower cable and phone line. If that 'arrestor' does not : connect AC electric wire to earth ground, then a transient : (again in that picture) goes into fax machine (modem) on L : connection, then destructively out on phone wires to NID and : to earth ground. Above demonstrates why fax machines, modems, : and portable phone bases stations are so often damaged by AC : electric wire transients. === Wow, those are some huge assumptions and incorrect at that. That come nowhere close to explaining why fax machines etx. are so often damaged by electric wire transients. In reality, if you research for facts just a little bit, you'll find that most telephone appliances are damaged by transients because they have NO protection, or under rated protection. Lightning is NOT the overwhelming reason for damage to those components. Lightning is one of the least controllable damage elements in existance. You can only partially protect against small, almost tiny lightning hits. Most transients are generated from other sources, the majority of them being inductive loads, grid controlling elements in the ac plants, transformer problems, and even the loads and motors within a building itself. I don't object to someone trying to help things out; I do object to obvious rationalizations and attempts to justify things to one's own "feelings" of how something should be. The world just isn't'' like that. : : Above is pre-WWII technology now made necessary in dwellings : due to something new - transistors. Transistor protection is : often little understood by some electricians who only : understand NEC requirements. === NEC requirements have NO, nada, zero, consideration for the protection of semiconductor devices and thus is of no concern to "some electricians". I do think though that you're on shaky ground by saying they have no understanding - many actually do. NEC does not require transistor : protection. NEC is for human protection. Transistor : protection is defined by the most critical component in a : protection system: earth ground. === Oh, gosh, no. Earth ground has almost nothing to do with the actual protection. It's the RELATIVE electrical position of the references, whether it be a dc voltage, 0 volts, or even a high voltage, that matters. I can run a 3 Volt microprocessor on a 100V DC line if the other side of the line stays within 97 volts (or 103 as the case may be) of whichever is determined (chosen) to be the reference. Yes, 100V DC CAN be considered GROUND to a ckt and everything will work fine, including component protection against transients. Actually, you could look at some TV schematics to get an idea of how some of that works. : : Gfretwell has posted how homes are now being built so as to : provide superior transistor safety in pictures at: : http://members.aol.com/gfretwell/ufer.jpg : : Another also demonstrates better earthing. None of this : would be required if city water pipe was sufficient as earth : ground for transistor safety: : http://www.knology.net/~res0958z/ === Noo, that's NOT the reason water pipes aren't allowed as ground any longer. Actually, transistors being as old as they are, they were quite well protected by cold water pipes and the same standard surge protection used by many people today. That changed when it was no longer allowable to use water pipes for a safety earth, and as I've tried to indicate, it is almost a moot point to anything. You will still find many thousands of homes with water pipe grounds, with modern electonic equipment that works very well and just as well as any other system you can imagine. : : Above was earthing for secondary protection. Also necessary : is earthing for primary protection: : http://www.tvtower.com/fpl.html === I don't think you have any idea what primary and secondary mean here, do you? Enough soap boxing, I guess. I don't have anything else to say on the matter, so that is what I'm going to say. |
#19
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Ground Rod For House ?
The simple answer: Water pipe is no longer sufficient as a
building's earth ground. Post 1990 code requires other earthing electrode selected from the list in paragraphs (A)(2) through (A)(7) so that building earthing is sufficient and minimally acceptable. To reply to 'mixed within' inline replies: Yes, many homes have only water pipes for earthing. Eventually, all that will be corrected as we slowly upgrade to minimally acceptable ground standards. Many homes also have two prong wall receptacles. Is that acceptable today? Of course not. That also is slowly being corrected. Meanwhile for both human safety and for something new to homes (transistor safety), water pipe earthing is no long sufficient. Homeowner is encouraged to upgrade building earthing for more than human safety reasons. Transistor? Show me any IC that does not have transistors? Furthermore, transistors - discrete parts - are widely used in most every electronic device. I am responding here to something that Pop should have obviously known by looking at the PC board even on a disk drive. He also ignores unnecessary transistor damage from decades previous. A solution that begins with sufficient earthing. No, I have not used resistance and impedance interchangeably. Mercy! Read what was posted carefully to appreciate specific references to each. Comprehending impedance is necessary appreciate electrical concepts in that fax machine example; why so much unnecessary transistor damage has occurred for so many decades. NID contains protection that was once only an arc over device - gas discharge tube or GDT. Appreciate why earthing is essential for phone circuits - why GDTs work. If one thinks any protector blocks or absorbs destructive transients, then one never learned what effective protection does. NID does provide effective transistor protection - but only as good as its earth ground. Where does the human start to eliminate transistor damage? Earth ground as even demonstrated in that previous www.tvtower.com citation. BTW your 600 volt number is an obsolete 1950s standard that was once 400 to 600 volts. Times and protectors have changed. I make no assumptions or rationalizations having learned this stuff decades ago as an engineer and from experience. It is routine to protect from direct lightning strikes as even addressed by Bodle and Gresh in their Mar 1961 paper in the Bell System Technical Journal. And yes, they are discussing 'transistor' protection back then. Their paper even demonstrates why underground utility wires require properly earthed service entrance protection. There was no rationalization. You are apparently having difficulty even with concepts of impedance verses resistance. Those who are not familiar also might post: Oh, gosh, no. Earth ground has almost nothing to do with the actual protection. Earthing is THE one essential component that literally every building protection system requires. Pop: Read highly regarded application notes from Polyphaser. Does Polyphaser discuss their product line? Of course not. Polyphaser discusses THE most critical component in protection - earth ground: http://www.polyphaser.com/ppc_ptd_home.aspx Many science papers dating back even to the 1930s define effective protection as based upon techniques pioneered by Ben Franklin in 1752. Was Franklin also rationalizing? Were GE and Westinghouse researchers rationalizing when their equipment atop the Empire State Building could suffer about 25 direct strikes annually without damage? What was posted is well proven science. But many today still remain in denial. In denial even about what the NEC now demands for earthing a building only for human safety. Water pipe earth ground is no longer sufficient as a building's only earth ground. This also for so many reasons provided in previous posts. This proven by literally quoting NEC text. And yet still many will deny what the NEC itself demands. Water pipe earth ground is no longer sufficient to earth a building. Above is about transistor safety. Different from what the Original Poster asks and what NEC addresses with demands for supplemental earthing. A water pipe earth ground is no longer sufficient. Pop, looking forward to questions once you have learned from Polyphaser's app notes. Yes, those wires atop telephone poles are little different from radio station antenna. As the Polyphaser app notes will demonstrate, underground wires are also at risk. All three connect directly to transistors inside a building. Transistor protection is only as effective as its earth ground. Pop wrote: Mercy! I'm not quite sure what you're trying to say here, or what the point of some of the irrelevant URLs/comments might be, but ... either you need to step back and put your heard around this again, or seek further education and experience. You'll probably object to my post here, but it's so typical of many on this group lately that I just can't hold it in any longer. Those who have nothing to say, should say exactly that. Those who do have something to say, should be clear and concise about it. Rationalization and guessing have no place in the realm of safety. |
#20
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Ground Rod For House ?
An example demonstrates the earthing problem. A 12 AWG wire
from wall receptacle maybe 50 feet back to mains box has less than 0.2 ohms resistance. That same wire would have something like 120 ohms impedance. Lets say a tiny 100 amp transient seeks earth ground via that 50 foot wire. Therefore a wall receptacle - and adjacent electronics - will be at something less than 12,000 volts. Will that transient seek earth via that safety ground wire? Of course not. It will also seek other and destructive paths via adjacent electronics. Wire length is but one reason why a wall receptacle safety ground is not sufficient as earth ground. Also explains why plug-in protectors are so ineffective. Essential to minimizing wire impedance are wire length, no sharp bends, and other characteristics cited previously. Also important is a concept cited by Bud-- Clamping all incoming wires to the same the same ground reference is the best way I know to protect electronics. ... The quality of a service entrance protector is only as effective as its earth ground which is why distance to that earthing is so critical and why single point earthing is essential. That means the 6 AWG wire does not go up over a foundation and then down to an earth ground rod. That wire goes through foundation somewhere just above the ground rod so that wire distance is shorter with sharp bends eliminated. Also important is that earthing wire remain separated from other non-earthing wires to avoid induced transients. Yes, lower resistance does help which is why high reliability facilities such as electric substations expand their earth ground to also lower resistance. It is also why earthing should be planned when the footing are poured. Equipotential being another aspect of superior earthing. Unfortunately we still don't build as if the transistor exists. We still do earthing as an afterthought. Effective earthing addresses concepts in excess of that performed by conventional household earthing. Equipotential being a concept of transistor protection that is not as essential to human protection. If we built buildings for effective transistor protection, then Ufer grounds would be routine; and not some afterthought to supplement water pipe ground such as ground rods. Even water pipe would enter a building adjacent to all other utilities to contribute to transistor safety. Even NEC requires all incoming electrical utilities be earthed to a common point for human safety - a problem still found even in some new homes. That 20 foot requirement from NEC is article 800.40(A)(4): Length. The primary protector grounding conductor shall be as short as practicable. In one- and two-family dwellings, the primary protector grounding conducutor shall be as short as practicable, not to exceed 6.0 meters (20 ft) in length. Same paragraphs is also found in Article 820. Cinergy demonstrates how to solve earthing problems created when utilities arrive at wrong locations. A problem often created by service installers or builders who still have not learned about proper earthing: http://www.cinergy.com/surge/ttip08.htm Concrete encased grounding (Ufer grounds) were so well proven even before WWII as to even protect munitions from direct lightning strikes. If water pipe earthing was so effective, then why do they implement Ufer grounding even in buildings with water pipe grounds? Halo grounds are but another way of improved earthing. Again, to answer the original poster's question - water pipe earthing alone is no longer sufficient to meet code. Upgrade to accomplish more than just meet code. Transistor protection is only as effective as a building's earth ground. Bud-- wrote: As I said protector blocks for cable and TV should be immediately adjacent to the panel so all wiring is clamped to the same ground reference. You don't explain how a ground rod would help in this instance. Adding a ground rod near the FAX is not going to provide a low impedance to keep the ground reference for the FAX the same as the incoming neutral. ... Incoming utilities listed have to have protector blocks near the power panel to get a common grounding reference. How does a 10 foot wire to a high resistance ground rod provide a lower ground impedance than a grounding electrode conductor and water pipe? This is cental to your arguments. Perhaps you could explain and also provide some citations that support your view. For a 500A service the conductor to a ground rod has to be #6. The conductor to a water pipe has to be 2/0 - 3.5 x the area. How come? Surges include high frequency components for which impedance is important. Grounding electrode conductor and water pipe has one function of limiting surges. Another problem with using a cold water pipe as an earth ground connection - code wants each utility to be earthed less than 20 feet to the common point. Cite the code. ... Clamping all incoming wires to the same the same ground reference is the best way I know to protect electronics. That requires the protector blocks to be near the electrical panel. (More properly thay have to be near each other.) That is likely a lot more important than resistance or impedance to ground. If all wiring was clamped to the same reference with no ground connection could electronics see a difference. Gfretwell has posted how homes are now being built so as to provide superior transistor safety in pictures at: http://members.aol.com/gfretwell/ufer.jpg This is a concrete encased electrode which I said is probably the second best electrode (after water pipes). It is one of 3 electrodes that must be included in a ground system, if present. (The other 2 are water pipe and building steel, which a home doesn't have.) Not included: ground rod. Another also demonstrates better earthing. None of this would be required if city water pipe was sufficient as earth ground for transistor safety: http://www.knology.net/~res0958z/ Most of us don't put 55 foot high lightning rods in our back yard. Not particualrly relevant. ------------- With regard to: Bud-- does not even quote code to justify his post. You do not understand why water pipes are required to have a SUPPLEMENTAL electrode and don't listen to people who do understand. Since arguing the code is pointles, I tried Physics - ground resistance. That doesn't seem to work either. bud-- |
#21
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Ground Rod For House ?
w_tom wrote:
An example demonstrates the earthing problem. A 12 AWG wire from wall receptacle maybe 50 feet back to mains box has less than 0.2 ohms resistance. That same wire would have something like 120 ohms impedance. Lets say a tiny 100 amp transient seeks earth ground via that 50 foot wire. Therefore a wall receptacle - and adjacent electronics - will be at something less than 12,000 volts. Will that transient seek earth via that safety ground wire? Of course not. It will also seek other and destructive paths via adjacent electronics. Wire length is but one reason why a wall receptacle safety ground is not sufficient as earth ground. Also explains why plug-in protectors are so ineffective. I never talked about branch ckts and don't want to start now. If I did I would want a citation for 120 ohms. Impedance of ground rod and water pipe would be relevant. Concrete encased grounding (Ufer grounds) were so well proven even before WWII as to even protect munitions from direct lightning strikes. If water pipe earthing was so effective, then why do they implement Ufer grounding even in buildings with water pipe grounds? Perhaps because a supplementary ground is required for a water pipe because it may be replaced by plastic and ground rods are way worse than either. Not obvious who "they" are. If it is gfretwell, in a current thread he says the gound conductivity near him is very bad. Sounds like the Ufer is a foundation ring. An unrelated video tape shows driving a 10' rod in Florida with a water table about 3' down, connecting 120V and getting a current of about 1.5A (implies 80 ohms ground resistance). Halo grounds are but another way of improved earthing. Probably mean ground ring in NEC. Phaser uses halo (in the air) and it isn't what you want. ----------- I actually only planned to respond to your citations in response to me and pop: Cinergy demonstrates how to solve earthing problems created when utilities arrive at wrong locations. A problem often created by service installers or builders who still have not learned about proper earthing: http://www.cinergy.com/surge/ttip08.htm Cinergy in effect talks about a common ground reference which I have emphasized several times. We probably substantialy, but not entirely agree on this. Nothing on water pipes and ground rods which we don't agree on. Where does the human start to eliminate transistor damage? Earth ground as even demonstrated in that previous www.tvtower.com citation. I have no idea what at that site is relevant Polyphaser discusses THE most critical component in protection - earth ground: http://www.polyphaser.com/ppc_ptd_home.aspx The most consistent protection in the papers is having a common ground reference for power and signal. They talk about using ground rods only to ground towers - which constitute large lightning rods. No one protects their house from direct lightning strikes unless they install lightning rods/air terminals. Most of the info is specific to lightning, towers and antenna coax - not particularly relevant to grounding elsewhere. If you are going to cite it you should pick out the relevant papers, if any. bud-- |
#22
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Ground Rod For House ?
That's a grand collection of misquotes and minsinformation and
hooey references that are irrelevant to most anything here. Like I said before, I'm not inclined to continue to debate these OT side trips of useless misinformation. If you'd like to have a sensible, detailed debate, start a new thread where it belongs. People are beginning to complain about responses that have nothing to do with the OP's questions, and I have to agree it does make it hard to find a meaningful response if there is one. "w_tom" wrote in message ... : The simple answer: Water pipe is no longer sufficient as a : building's earth ground. Post 1990 code requires other : earthing electrode selected from the list in paragraphs : (A)(2) through (A)(7) so that building earthing is sufficient : and minimally acceptable. : : To reply to 'mixed within' inline replies: Yes, many homes : have only water pipes for earthing. Eventually, all that will : be corrected as we slowly upgrade to minimally acceptable : ground standards. Many homes also have two prong wall : receptacles. Is that acceptable today? Of course not. That : also is slowly being corrected. : : Meanwhile for both human safety and for something new to : homes (transistor safety), water pipe earthing is no long : sufficient. Homeowner is encouraged to upgrade building : earthing for more than human safety reasons. : : Transistor? Show me any IC that does not have transistors? : Furthermore, transistors - discrete parts - are widely used in : most every electronic device. I am responding here to : something that Pop should have obviously known by looking at : the PC board even on a disk drive. He also ignores : unnecessary transistor damage from decades previous. A : solution that begins with sufficient earthing. : : No, I have not used resistance and impedance : interchangeably. Mercy! Read what was posted carefully to : appreciate specific references to each. Comprehending : impedance is necessary appreciate electrical concepts in that : fax machine example; why so much unnecessary transistor damage : has occurred for so many decades. : : NID contains protection that was once only an arc over : device - gas discharge tube or GDT. Appreciate why earthing : is essential for phone circuits - why GDTs work. If one : thinks any protector blocks or absorbs destructive transients, : then one never learned what effective protection does. NID : does provide effective transistor protection - but only as : good as its earth ground. Where does the human start to : eliminate transistor damage? Earth ground as even : demonstrated in that previous www.tvtower.com citation. : : BTW your 600 volt number is an obsolete 1950s standard that : was once 400 to 600 volts. Times and protectors have changed. : : I make no assumptions or rationalizations having learned : this stuff decades ago as an engineer and from experience. It : is routine to protect from direct lightning strikes as even : addressed by Bodle and Gresh in their Mar 1961 paper in the : Bell System Technical Journal. And yes, they are discussing : 'transistor' protection back then. Their paper even : demonstrates why underground utility wires require properly : earthed service entrance protection. : : There was no rationalization. You are apparently having : difficulty even with concepts of impedance verses resistance. : Those who are not familiar also might post: : Oh, gosh, no. Earth ground has almost nothing to do with : the actual protection. : Earthing is THE one essential component that literally every : building protection system requires. Pop: Read highly : regarded application notes from Polyphaser. Does Polyphaser : discuss their product line? Of course not. Polyphaser : discusses THE most critical component in protection - earth : ground: : http://www.polyphaser.com/ppc_ptd_home.aspx : : Many science papers dating back even to the 1930s define : effective protection as based upon techniques pioneered by Ben : Franklin in 1752. Was Franklin also rationalizing? Were GE : and Westinghouse researchers rationalizing when their : equipment atop the Empire State Building could suffer about 25 : direct strikes annually without damage? What was posted is : well proven science. But many today still remain in denial. : In denial even about what the NEC now demands for earthing a : building only for human safety. : : Water pipe earth ground is no longer sufficient as a : building's only earth ground. This also for so many reasons : provided in previous posts. This proven by literally quoting : NEC text. And yet still many will deny what the NEC itself : demands. Water pipe earth ground is no longer sufficient to : earth a building. : : Above is about transistor safety. Different from what the : Original Poster asks and what NEC addresses with demands for : supplemental earthing. A water pipe earth ground is no longer : sufficient. Pop, looking forward to questions once you have : learned from Polyphaser's app notes. Yes, those wires atop : telephone poles are little different from radio station : antenna. As the Polyphaser app notes will demonstrate, : underground wires are also at risk. All three connect : directly to transistors inside a building. Transistor : protection is only as effective as its earth ground. : : Pop wrote: : Mercy! I'm not quite sure what you're trying to say here, or : what the point of some of the irrelevant URLs/comments might be, : but ... either you need to step back and put your heard around : this again, or seek further education and experience. : You'll probably object to my post here, but it's so typical of : many on this group lately that I just can't hold it in any : longer. Those who have nothing to say, should say exactly that. : Those who do have something to say, should be clear and concise : about it. Rationalization and guessing have no place in the : realm of safety. |
#23
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Ground Rod For House ?
"w_tom" wrote in message ... : An example demonstrates the earthing problem. A 12 AWG wire : from wall receptacle maybe 50 feet back to mains box has less : than 0.2 ohms resistance. That same wire would have something : like 120 ohms impedance. At what frequency, and what are the approx reactive components? See, this is the kind of non-information I'm talking about. Lets say a tiny 100 amp transient : seeks earth ground via that 50 foot wire. Therefore a wall : receptacle - and adjacent electronics - will be at something : less than 12,000 volts. Time? Duration? Energy? What is the power in each component? Think about it. Will that transient seek earth via : that safety ground wire? Of course not. It will also seek : other and destructive paths via adjacent electronics. No, ALL freqs/rise/falls will not seek the same path. Think about it. : : Wire length is but one reason why a wall receptacle safety : ground is not sufficient as earth ground. Also explains why : plug-in protectors are so ineffective. I don't recall anyone saying that was the case. Did they? : : Essential to minimizing wire impedance are wire length, no : sharp bends, My gosh, what are you doing, applying field theory and waveguides? This is exactly what makes your possibly well intentioned information so useless. I'm surprised you left out the skin effect and a few other nice nouns you could have dropped in there. and other characteristics cited previously. Also : important is a concept cited by Bud-- : Clamping all incoming wires to the same the same ground : reference is the best way I know to protect electronics. ... Where did anyone claim it wasn't? The "best" wasn't the question; sufficient or acceptable were the words, IIRC. : The quality of a service entrance protector is only as : effective as its earth ground which is why distance to that : earthing is so critical and why single point earthing is : essential. That means the 6 AWG wire does not go up over a : foundation and then down to an earth ground rod. That wire : goes through foundation somewhere just above the ground rod so : that wire distance is shorter with sharp bends eliminated. Uhh, the sharp bends problem isn't for impedance or electrical considerations; it's physical properties related. Think about what you're saying. : Also important is that earthing wire remain separated from : other non-earthing wires to avoid induced transients. I don't think that was any part of the subject; true but not directly relevant. : : Yes, lower resistance does help which is why high : reliability facilities such as electric substations expand : their earth ground to also lower resistance. It is also why : earthing should be planned when the footing are poured. : Equipotential being another aspect of superior earthing. Superior earthing: What's that go to do with anything? Completely irrelevant to the subject matter. : : Unfortunately we still don't build as if the transistor : exists. We still do earthing as an afterthought. Effective : earthing addresses concepts in excess of that performed by : conventional household earthing. Equipotential being a : concept of transistor protection that is not as essential to : human protection. If we built buildings for effective : transistor protection, then Ufer grounds would be routine; and : not some afterthought to supplement water pipe ground such as : ground rods. Even water pipe would enter a building adjacent : to all other utilities to contribute to transistor safety. More irrelevance; no point to the entire para. : : Even NEC requires all incoming electrical utilities be : earthed to a common point for human safety - a problem still : found even in some new homes. "Even NEC"? .... More attempts at double-speak and name dropping clipped. : : Again, to answer the original poster's question - water pipe : earthing alone is no longer sufficient to meet code. Upgrade : to accomplish more than just meet code. Transistor protection : is only as effective as a building's earth ground. To take your bent for a moment, a "transistor" is defined as an e-b-c junction with physical leads attached. Semiconductor technology does indeed use the concept of transistors within chips et al for analogic discussion, but they are not transistors unless, like you, a person wished to take the word apart into its components, and work from there. It's also possible, still in your realm of fuzziness, to build a computer system with NO earth reference, but with controlled references, which will operate perfectly. I used to use such a system daily in my routine daily work for many years. And BTW, resistance IS a component of Impedance. If you wish to use the terms interchangeably, you need to add the words pure and reactance to your talk. Don't be a blatherskite. : : Bud-- wrote: : As I said protector blocks for cable and TV should be immediately : adjacent to the panel so all wiring is clamped to the same ground : reference. You don't explain how a ground rod would help in this : instance. Adding a ground rod near the FAX is not going to provide : a low impedance to keep the ground reference for the FAX the same : as the incoming neutral. : ... : : Incoming utilities listed have to have protector blocks near the power : panel to get a common grounding reference. : : How does a 10 foot wire to a high resistance ground rod provide a lower : ground impedance than a grounding electrode conductor and water pipe? : This is cental to your arguments. Perhaps you could explain and also : provide some citations that support your view. : : For a 500A service the conductor to a ground rod has to be #6. The : conductor to a water pipe has to be 2/0 - 3.5 x the area. How come? : Surges include high frequency components for which impedance is : important. Grounding electrode conductor and water pipe has one : function of limiting surges. : : Another problem with using a cold water pipe as an earth : ground connection - code wants each utility to be earthed less : than 20 feet to the common point. : : Cite the code. : ... : : Clamping all incoming wires to the same the same ground reference : is the best way I know to protect electronics. That requires the : protector blocks to be near the electrical panel. (More properly : thay have to be near each other.) That is likely a lot more : important than resistance or impedance to ground. If all wiring : was clamped to the same reference with no ground connection could : electronics see a difference. : : Gfretwell has posted how homes are now being built so as to : provide superior transistor safety in pictures at: : http://members.aol.com/gfretwell/ufer.jpg : : This is a concrete encased electrode which I said is probably the second : best electrode (after water pipes). It is one of 3 electrodes that must : be included in a ground system, if present. (The other 2 are water pipe : and building steel, which a home doesn't have.) Not included: ground rod. : : Another also demonstrates better earthing. None of this : would be required if city water pipe was sufficient as earth : ground for transistor safety: : http://www.knology.net/~res0958z/ : : Most of us don't put 55 foot high lightning rods in our back yard. Not : particualrly relevant. : : ------------- : With regard to: Bud-- does not even quote code to justify his post. You : do not understand why water pipes are required to have a SUPPLEMENTAL : electrode and don't listen to people who do understand. Since arguing : the code is pointles, I tried Physics - ground resistance. That doesn't : seem to work either. : : bud-- |
#24
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Ground Rod For House ?
In article , w_tom
wrote: ... Why does code also require a second earth ground rod if earth resistance is too high (25 ohms)? Second rod would not be necessary if water pipe was sufficient as an earth ground. But again, water pipe is no longer sufficient as an earth ground. Water pipe must be supplemented by something that is sufficient for earthing. Second copper clad rod may be required because an earth ground rod (or any other electrode from the list (A)(2) through (A)(7) ) is now the essential earthing electrode. It supplements making water pipe only a secondary and insufficient earth ground; as overtly stated in 250.53(D)(2) - quoted previously. ... Not sure how wise it is to add to this discussion, but... You may want to consult a qualified commentary book on the NEC for better explanations. One that I found extremely helpful is Practical Electrical Wiring, 18th Edition (2002 NEC) by Richter and Hartwell. It's been around awhile, the latest author Hartwell is a master electrician and Code Panel member, and I think this book has been endorsed numerous times in this conference. It explains (Chapter 16: Installing Service Entrances and Grounds): "In a large city with cast iron water mains and everyone connected through copper water laterals, the total resistance to ground from any given connection [on your water pipe] may be less than 1 ohm, about as good as possible." It goes on to say that the reason for requiring supplementary electrodes (per NEC 250.53 as you quote) is due to possible future replacement of water supply pipe with plastic or insertion of dielectric unions. If that has not taken place, the pipe is by far the best grounding electrode the average house can hope for. This correlates with what the electricians in this newsgroup have been stating. I have an older house with no supplementary electrode, but will be installing one (probably with 3 or 4 rods) to comply with Code when I upgrade my service. But with a 3/4" copper supply pipe entering my basement, buried about 10' deep for the 30' straight run to the main line in the street, and countless miles of deeply buried main water lines connected to that... How could a couple of 5/8" diameter, 8' long rods in my yard ever compete with that? If a lightning-induced surge came down my wires after I installed the rods, I'd have to wonder if more than even a few percent of the amps would choose to drain out in the sand and clay around those grounding rods instead of into the water main network. If that supply pipe were replaced with plastic, then yes, the grounding rods would become vital, and that's why (in my understanding) they are required by NEC 250.53(D) as preemptive protection against that change. |
#25
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Ground Rod For House ?
Hey Pop. You remember what transistors are? They are
things you said are not inside electronics today. Transistors - those things found inside integrated circuits no longer exist? That is my point. You argue without a technical grasp of reality - including a claim that transistors are no longer used. The code is quite specific. That water pipe earth ground is not longer sufficient to earth a building. The only misinformation is the 'missing information' posted by Pop. He does not comprehend quoted that he then insults. One day Pop will make a claim supported by facts and numbers. Not today. He still insists there are no transistor inside integrated circuits. Pop wrote: That's a grand collection of misquotes and minsinformation and hooey references that are irrelevant to most anything here. Like I said before, I'm not inclined to continue to debate these OT side trips of useless misinformation. If you'd like to have a sensible, detailed debate, start a new thread where it belongs. People are beginning to complain about responses that have nothing to do with the OP's questions, and I have to agree it does make it hard to find a meaningful response if there is one. |
#26
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Ground Rod For House ?
Provided was an example of wire impedance (it was not a
discussion of branch circuits); which explains WHY each earth ground connection must be short, no splices, no sharp bends, not inside metallic conduit, etc. Wire has impedance which is why short wire length is critical to earthing for transistor protection. To repeat what was posted: Cinergy also demonstrates solutions to bad construction - where the utilities don't enter at a common location. The need for single point earthing is good for human safety but essential to transistor safety. Above is about earthing for the secondary protection 'system'. www.tvtower.com demonstrates earthing of the primary protection 'system'. Layered protection 'systems'. Each layer of protection is defined by its single point earth ground. http://www.tvtower.com/fpl.html also demonstrates another earth ground that contributes to transistor protection. Polyphaser discusses protecting incoming wires from lightning. If your house is not adjacent to a 50 foot radio tower, then a 'tower' that lightning seeks is your house or those utility poles that connect directly to household transistors. Earthing that applies to protecting radio towers also applies to home protection. To lightning, that tower and those incoming house wires are same. But then Polyphaser - an industry benchmark - discusses more that just radio towers. What does Polyphaser discuss? Their products? Of course not. Polyphaser discusses earthing - the most critical component also in a home protection system. What is discussed here? Earthing the house - for same reasons that Polyphaser describes in: http://www.polyphaser.com/ppc_ptd_home.aspx Same principle that were once standard in places that had electronics - radio stations and telephone switching stations - are now necessary in other buildings that also have electronics - the home. Why extensive earthing of those FL homes? http://members.aol.com/gfretwell/ufer.jpg Again, water pipe earth ground alone just is not sufficient. Not sufficient to meet code AND not sufficient to protect household transistors. Bud-- wrote: w_tom wrote: I never talked about branch ckts and don't want to start now. If I did I would want a citation for 120 ohms. Impedance of ground rod and water pipe would be relevant. ... Perhaps because a supplementary ground is required for a water pipe because it may be replaced by plastic and ground rods are way worse than either. Not obvious who "they" are. If it is gfretwell, in a current thread he says the gound conductivity near him is very bad. Sounds like the Ufer is a foundation ring. An unrelated video tape shows driving a 10' rod in Florida with a water table about 3' down, connecting 120V and getting a current of about 1.5A (implies 80 ohms ground resistance). ... Probably mean ground ring in NEC. Phaser uses halo (in the air) and it isn't what you want. ----------- I actually only planned to respond to your citations in response to me and pop: ... Cinergy in effect talks about a common ground reference which I have emphasized several times. We probably substantialy, but not entirely agree on this. Nothing on water pipes and ground rods which we don't agree on. Where does the human start to eliminate transistor damage? Earth ground as even demonstrated in that previous www.tvtower.com citation. I have no idea what at that site is relevant Polyphaser discusses THE most critical component in protection - earth ground: http://www.polyphaser.com/ppc_ptd_home.aspx The most consistent protection in the papers is having a common ground reference for power and signal. They talk about using ground rods only to ground towers - which constitute large lightning rods. No one protects their house from direct lightning strikes unless they install lightning rods/air terminals. Most of the info is specific to lightning, towers and antenna coax - not particularly relevant to grounding elsewhere. If you are going to cite it you should pick out the relevant papers, if any. bud-- |
#27
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Ground Rod For House ?
Reasons provided for the supplementary electrode - plastic
pipe, etc - are what most agree on. What some non-electricians are having a problem with are other electrical and electronic reasons why a water pipe ground is not sufficient. Involves parameters that concern engineers - that include and go beyond an electrician's code requirements. Remember, code is only about human safety. But the earthing system also performs other functions - such as transistor safety. One reason why a water pipe ground is not sufficient - it does not belong to the electrical system and therefore can be compromised: plumber disconnects a pipe that is electrically hot, plumber installs plastic pipe, etc. All these reasons provided previously are not in dispute (except where one only wants to argue). Your reasoning only assumes resistance. Grasped the concept of impedance. Resistance of ground rods at signficantly less than 25 ohms is sufficient for transistor protection. So if you lower resistance to 2 ohms, have you improve things by 10 times? Of course not. 2 ohms is only a minor improvement - provides a marginal improvement. Lowering resistance provides an exponentially decreasing advantage. But impedance, as discussed elsewhere, is a major bottleneck to transistor safety. If water pipe ground was so good, then why do high reliability facilities that only used copper water pipes still install Ufer, wire mesh, and other grounds as demonstrated in: http://members.aol.com/gfretwell/ufer.jpg The water pipe ground with all that lower resistance is still not sufficient for earthing. Again, if looking at resistance, then other aspects of earthing, summarized in previous posts, are being ignnored. Notice why those posts are so long. Notice the so many application notes about earthing for laymen at: http://www.polyphaser.com/ppc_ptd_home.aspx There is more to earthing than just low resistance. If you only want to meet code, then only worry only about resistance. But reasons why others don't rely on a water pipe ground are found in electrical concepts such as impedance and equipotential. These are parameters that electricians need not learn, are not part of the human safety code, and have been made important by household transistors. The code says water pipe must be supplemented for things such as plastic pipe and plumber safety. But facilities that had transistors decades ago supplemented that water pipe ground for electrical reasons that will never be part of human safety code (NEC). Those same reasons for better earthing (such as halo or Ufer grounds) are now in your house. chocolatemalt wrote: Not sure how wise it is to add to this discussion, but... You may want to consult a qualified commentary book on the NEC for better explanations. One that I found extremely helpful is Practical Electrical Wiring, 18th Edition (2002 NEC) by Richter and Hartwell. It's been around awhile, the latest author Hartwell is a master electrician and Code Panel member, and I think this book has been endorsed numerous times in this conference. It explains (Chapter 16: Installing Service Entrances and Grounds): "In a large city with cast iron water mains and everyone connected through copper water laterals, the total resistance to ground from any given connection [on your water pipe] may be less than 1 ohm, about as good as possible." It goes on to say that the reason for requiring supplementary electrodes (per NEC 250.53 as you quote) is due to possible future replacement of water supply pipe with plastic or insertion of dielectric unions. If that has not taken place, the pipe is by far the best grounding electrode the average house can hope for. This correlates with what the electricians in this newsgroup have been stating. I have an older house with no supplementary electrode, but will be installing one (probably with 3 or 4 rods) to comply with Code when I upgrade my service. But with a 3/4" copper supply pipe entering my basement, buried about 10' deep for the 30' straight run to the main line in the street, and countless miles of deeply buried main water lines connected to that... How could a couple of 5/8" diameter, 8' long rods in my yard ever compete with that? If a lightning-induced surge came down my wires after I installed the rods, I'd have to wonder if more than even a few percent of the amps would choose to drain out in the sand and clay around those grounding rods instead of into the water main network. If that supply pipe were replaced with plastic, then yes, the grounding rods would become vital, and that's why (in my understanding) they are required by NEC 250.53(D) as preemptive protection against that change. |
#28
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Ground Rod For House ?
Hmm, , you're pretty closed minded and ignorant. When you can't
confuse someone with rationalization disguised as facts you get "interesting". I suspected a troll early on - too bad I and others bothered to feed you. |
#29
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Ground Rod For House ?
Not sure how wise it is to add to this discussion, but... Might have been the best post in the thread. bud-- |
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