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

Reply to
Robert11
Loading thread data ...

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

Reply to
Speedy Jim

Reply to
w_tom

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.

Reply to
Tom Horne, Electrician

For those who don't know, Edison's first working municipal electrical system was DC.

Commodore Joe Redcloud©

Reply to
Commodore Joe Redcloud©

That's exactly why he said ac was dangerous. He had a vested interest in the use of DC.

Bob

Reply to
Robertm

Which he actually developed into the electric chair:

formatting link
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

Reply to
spudnuty

And, considering what he wanted AC to be used for, "Westinghouse" was once a synonym for "electrocute".

Reply to
Mark Lloyd

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):

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 > W Tom
Reply to
w_tom

Which is why his opponents, the competing company, were able to say that DC was dangerous,

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.

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.

Reply to
mm

w_tom wrote:

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

formatting link

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
Reply to
Thomas D. Horne, FF EMT

"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.

Reply to
trader4

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:

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 earth> Quoting only part of the applicable section of the code does you no
Reply to
w_tom

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.

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.

Never explained - why the lowest resistance isn't the best protection.

Numerous reasons - never stated.

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.

Reply to
Bud--

What is this "transistor safety" that you keep talking about?

Please explain.

Reply to
Oscar_Lives

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:

formatting link
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 >> What you have described as a "grounding electrode system" is

Reply to
w_tom

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 reas> To the OP: if you are going to post the same message to multiple

Reply to
w_tom

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.

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.

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.

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--

Reply to
Bud--

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 news: snipped-for-privacy@hotmail.com... : 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: :

formatting link
: 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: :

formatting link
: Another also demonstrates better earthing. None of this : would be required if city water pipe was sufficient as earth : ground for transistor safety: :
formatting link
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: :

formatting link
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.

Reply to
Pop

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

formatting link
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:

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:

formatting link
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 l> Mercy! I'm not quite sure what you're trying to say here, or

Reply to
w_tom

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.