Panel Grounding vs. Lightning Rod Grounding

. Poor w_ can't read.

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 .... .

. Poor w_ can't read:

250.50 Grounding Electrode System... All grounding electrodes as described in 250.52(A)(1) through (A)(6) that are present at each building or structure served shall be bonded together to form the grounding electrode system. 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 ....

As anyone with half a brain can determine, water pipes are *required* to be an electrode. .

. The NEC has separate (less strict) rules for "bonding" the interior water pipe that apply if the buried water pipes are plastic. Otherwise the interior pipes are bonded by the required earthing connection. .

. Nothing except NEC 250.50. It is amazing how 2 people can=92t read what the NEC clearly says.

-- bud--

. You are right about the superiority of a municipal water system over a rod. The problems is conversion of municipal water systems to plastic. Apparently it is common enough that a "supplemental" electrode makes sense as insurance. A ground rod is usually easy to install. A "concrete encased electrode" is a lot more hassle. .

. w_ has a rather low opinion of plumbers. Connection to the water pipe has been required to be within 5 feet of the entrance point for many years, with a bond wire across the water meter. .

. So w_ believes you shouldn't include the superior electrode. .

. When the water pipe is an earthing electrode, grounding connections can still be made in the first 5 feet inside the building, the same as the earthing electrode connection.

Connections made elsewhere that were code compliant when made are still code compliant. .

. The NEC has separate rules for "bonding" the interior water pipe that apply if the buried water pipes are plastic. Bonding location is not specified. .

. A "supplemental" electrode is only required in new installations. There are millions of homes with only a water pipe electrode that are code compliant.

-- bud--

. You wrote: "This is simply not true. For many years NEC *allowed* us250=9681 Water pipe. A metallic underground water piping system, either local or supplying a community, shall always be used as the grounding electrode where such a piping system is available..

You have not expla250.50 Grounding Electrode System... All grounding electrodes as described in 250.52(A)(1) through (A)(6) that are present at each building or structure served shall be bonded together to form the grounding electrode system.

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 ....

You have not explained how water pipes are not *required* to be an electrode now - how they are no longer acceptable.

-- bud--

. Poor w_ can't read.

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 .... .

. Poor w_ can't read:

250.50 Grounding Electrode System... All grounding electrodes as described in 250.52(A)(1) through (A)(6) that are present at each building or structure served shall be bonded together to form the grounding electrode system. 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 ....

As anyone with half a brain can determine, water pipes are *required* to be an electrode.

there u go rlb. you should be able to understand that.

Wow. Amazing how many cannot read beyond one or two paragraphs. OK. Let's simplify the code for Bob and Bud.

Yes, code, the McGraw Hill book and w_tom all say the water pipe is an earthing electrode - defined by 250.52(A)(1).

Code, the book, and w_tom also say if the building has only a pipe electrode, then the building is not sufficiently (not adequately) earthed. Defined by 250.52(D)(2) entitled:

So what are these other electrodes 250.52(A)(2) through (A)(7)? If the building has any one of these electrodes, then the building IS sufficiently earthed. If the building has any one of these electrodes and a pipe electrode, then the building is sufficient earthed. If the building only has the water pipe electrode 250.52(A)(1), then the building IS NOT earthed.

Furthermore, if a building does have the pipe electrode, then that water pipe must be *bonded* to other electrodes. Because it is an electrode that is not sufficient, then that electrode must be bonded to any other electrode =96 as defined by 250.52(A)(2) through (A)(7).

Code is written for those who can read more than two paragraphs. Bob only reads two paragraphs and =91feels=92 he is an expert. Anyone with half a brain would read all paragraphs. Those other paragraphs say a water pipe electrode - alone - does not earth a building. 1) Other electrodes must be installed. And 2) if the water pipe electrode exists, then it must be bonded to other electrodes.

Bob, how do YOU bond the water pipe to another electrode when you say those other electrodes need not exist? Oh. You also forgot to read all paragraphs.

The McGraw Hill book also agrees with w_tom and the code. McGraw Hill also bluntly contradicts Bob and Bud:

How do we know both Bob and Bud are lying? Those who cannot defend themselves or do not have enough brain to read more than two paragraphs will routinely post mockery and insult. Insults and profanity are common from those who do not even have half a brain. Anyone with half a brain would have read all paragrasphs - know that the water pipe is not sufficient for earthing a building.

Bob read that a water pipe is an electrode. Bob then assumed any electrode is sufficient. Code is quite blunt about this. The > Poor w_ can't read.

I know code as it applies to lv. I do lv for a living for the last 30 years. I also don't care what you have to say about it. All I have to know is to ground everything in the same place with short runs and no sharp bends. lv guys don't do plumbing or put in ground rods. we just hook up to what is already there. if my equipment gets hit by lightening I make more money and I tell the homoaner if his house is not grounded properly. end of stroy. oh yea and I like to needle diyers.

Yes, code, the McGraw Hill book and w_tom all say the water pipe is an earthing electrode - defined by 250.52(A)(1).

Code, the book, and w_tom also say if the building has only a pipe electrode, then the building is not sufficiently (not adequately) earthed. Defined by 250.52(D)(2) entitled:

So what are these other electrodes 250.52(A)(2) through (A)(7)? If the building has any one of these electrodes, then the building IS sufficiently earthed. If the building has any one of these electrodes and a pipe electrode, then the building is sufficient earthed. If the building only has the water pipe electrode 250.52(A)(1), then the building IS NOT earthed.

Furthermore, if a building does have the pipe electrode, then that water pipe must be *bonded* to other electrodes. Because it is an electrode that is not sufficient, then that electrode must be bonded to any other electrode ? as defined by 250.52(A)(2) through (A)(7).

Code is written for those who can read more than two paragraphs. Bob only reads two paragraphs and ?feels? he is an expert. Anyone with half a brain would read all paragraphs. Those other paragraphs say a water pipe electrode - alone - does not earth a building. 1) Other electrodes must be installed. And 2) if the water pipe electrode exists, then it must be bonded to other electrodes.

Bob, how do YOU bond the water pipe to another electrode when you say those other electrodes need not exist? Oh. You also forgot to read all paragraphs.

The McGraw Hill book also agrees with w_tom and the code. McGraw Hill also bluntly contradicts Bob and Bud:

How do we know both Bob and Bud are lying? Those who cannot defend themselves or do not have enough brain to read more than two paragraphs will routinely post mockery and insult. Insults and profanity are common from those who do not even have half a brain. Anyone with half a brain would have read all paragrasphs - know that the water pipe is not sufficient for earthing a building.

Bob read that a water pipe is an electrode. Bob then assumed any electrode is sufficient. Code is quite blunt about this. The > Poor w_ can't read.

Which explains another fundamental. Proper earthing is best installed when the footing are poured. Everything after that tends to be a compromise - best make do with what exists.

Having said this, also best is to also install phone service, AC electric, cable TV, and alarm system as close as practical to the single point earth ground. Then upgrade that earthing as necessary to provide sufficient protection.

Nothing is 100% effective. Earthing can make protection nearly 100% effective OR contribute to electronics damage depending on how it is installed and connected. Protection will be as effective as that earthing.

Ok ..... your right.

Please go away now.

Honestly .... we DO believe you.

No kidding.

We really, really do

Cross my heart and hope Bass dies.

. w_=92s previous post that said "Pipes are not required to be an earthing electrode." w_ is backpedaling.

Required earthing electrodes are defined in 250.50. .

. A water pipe electrode is required to be connected with a "grounding electrode conductor". Rules for "bonding" a water pipe are different (less stringent) and apply only when water pipe is not min 10 ft metal in earth.

In fact it is the "supplemental" electrode that may be "bonded" to the earthing system (250.53(D)(2)). Why is the "supplemental" electrode only required to be "bonded" w_? .

Like electricians. Electricians at alt.home.repair regularly challenge w_=92s religious views (immune from challenge) on water pipes. (I am also an electrician.)

w_=92s posts are full of errors about what the code says.

w_=92s beliefs about this section of the code are even more bizarre than what he has said in this thread. .

. Poor w_ can=92t figure out why a "supplemental" electrode is required. Explained in the NFPA "National Electrical Code Handbook": "The requirement to supplement the metal water pipe is based on the practice of using plastic pipe for replacement when the original metal water pipe fails."

And w_ seems to miss that "WATER PIPE IS A SUTIABLE [sic] GROUNDING ELECTRODE".

There is nothing inadequate about water pipe except that it may be replaced with plastic.

Seems there is only one pigeon in this newsgroup w_.

-- bud--

Simple logic is difficult for sales promoters.

If a building's only earthing electrode is a water pipe, then the building IS NOT properly earthed.

If a building's only earthing electrode is any other electrode, then the building IS properly earthed.

If a water pipe electrode exists, then 1) some other earthing electrode must intalled AND 2) that water pipe electrode must be bonded to the other earthing electrode.

As Robert L Bass noted, earthing only to the cold water pipe once was acceptable. That has no longer been acceptable for about 20 years. If a water pipe earthing electrode exists, then some other earthing electrode must be installed to meet current code requirements.

Bud posts insults because Bud has again been exposed posting erroneously.

. Simple logic is difficult for religious fanatics. .

. Another post full of misinformation. Millions of buildings with only a water pipe ground are fully code compliant. .

. Not if there is a metal water service pipe. .

2) that water pipe electrode must be

. As has been pointed out more than once, water pipes are connected with a "grounding electrode conductor". They can not be "bonded" unless they are under 10 ft metal in the earth.

And as has been pointed out, "supplemental" electrodes can be bonded (less stringent requirement). .

. RLB said nothing about "only". It was not "acceptable", it was

*required*. Just as you said "Pipes are not required to be an earthing electrode." You have been backpedaling since. You both are wrong. .

. But poor w_ still can=92t figure out why. .

. w_ said "Pipes are not required to be an earthing electrode"? Water pipes are *required* to be used as an earthing electrode. ( Poor w_ said may times in many threads water pipes are not allowed to be used as earthing electrodes. It is a religious belief.)

w_ said "Nothing can be grounded to cold water pipes anywhere inside the structure." Connections can be made in the first 5 feet of entry. w_ said "Water pipes must be bonded to the electrical panel" Water pipes must be connected with a "grounding electrode conductor"9.

And why can "supplemental" electrodes be "bonded"? Must be they are backup protection.

-- bud--

Bud, as a novice, (I'm the OP), my interpretation is that these codes and standards, (e.g., NEC and NFPA), are intended to address human and structural safety, from the point-of-view of electrical and fire hazards. If so (?), this is certainly a noble and necessary goal. However, my intuition is uneasy that following these codes and standards will also protect one's electronics and security systems.

Specifically, if one is supposed to bond the downhaul conductors from the lightning rods on the roof to the main house grounding electrode, (to which all of the electronics and alarm panel are also bonded), I would agree that this should keep all of these components at the same potential during a lightning event, which should preclude arcing. But my intuition also says that the resulting surge into those components, from this common grounding, will most likely also take them out. Is my intuition on track?

Perhaps the correct question really should be, "which is more important to you, your stereo and alarm panel, or your @ss?". If the latter, then one should follow the regs, bond everything together, and just hope that one is not the recipient of a lightning event. Is my thinking on track?

Thank you very much for any thoughts.

. Geez - you survived this far. You must be well grounded.

They don=92t completely protect electronics, but not following the codes will make it harder to protect the electronics, in addition to reducing personal and structural safety.

The best information on surges and surge protection I have seen is at:

- "How to protect your house and its contents from lightning: IEEE guide for surge protection of equipment connected to AC power and communication circuits" published by the IEEE in 2005 (the IEEE is the major organization of electrical and electronic engineers in the US). And also:

"NIST recommended practice guide: Surges Happen!: how to protect the appliances in your home" published by the US National Institute of Standards and Technology in 2001

The IEEE guide is aimed at those with some technical background. The NIST guide is aimed at the unwashed masses.

The guides don=92t much address direct lightning strikes to your house. For most of us it would be a very rare event And it is a specialized field.

The surge protection principles from both guides are, in general:

1_ Adequate earthing of the building electrical system. The NEC requires earthing of systems. 2_ Short 'ground' wires from phone and cable entry protectors to the ground at the power service. The NIST guide, using US insurance information, suggests the major cause of damage to equipment is high voltage between power and signal wires (TVs, computers).

- With large surge current to earth the system ground can rise thousands of volts above "absolute" ground potential. Much of the protection is having all wires rise together. The author of the NIST guide has written "the impedance of the grounding system to `true earth' is far less important than the integrity of the bonding of the various parts of the grounding system."

- The IEEE guide has an example of a cable entry ground wire that is far too long starting pdf page 40. Recommended reading.

- Many houses have phone and cable entry points that are too far from the power service. (In that case the IEEE guide says "the only effective way of protecting the equipment is to use a multiport [plug- in] protector.")

3_ Service panel suppressors. These clamp (limit) the voltage from power wires to system ground. Since system ground is connected to an earthing electrode this dumps most of the surge energy coming in on a power service to earth. Since the system ground is also bonded to the neutral at US services the voltage from hot-to-neutral-to-ground is limited. The more lightning activity the more useful a service panel suppressor is. 4_ Plug-in suppressors. These are most useful on high value equipment, particularly if it attaches to both power and signal wires (like computer/modem, TV/related/cable).

- Note that all interconnected equipment needs to be connected to the same plug-in suppressor, or interconnecting wires need to go through the suppressor. External connections, like phone, also need to go through the suppressor. Connecting all wiring through the suppressor prevents damaging voltages between power and signal wires. These multiport suppressors are described in both guides.

- Plug-in suppressors do not primarily work by earthing the surge, that occurs elsewhere in the system. They clamp (limit) the voltage on all wires (power and signal) to the common ground at the suppressor.

If I was in a very high lightning area I would use all 4. .

. Even with a very low resistance-to-earth connection, the currents from a lightning strike will elevate the potential of the rod system far above "absolute" ground potential. If you don=92t bond, you will have a system of lightning rods and conductors that can be tens of thousands of volts different from the house =91ground=92 system. Direct arcs to the building systems can span a long distance.

Even with the bonding, the impedance of the lightning rod conductors for a lightning strike is high enough you can have side flashes. I noted that NFPA 780 says electrical system 'grounded' metal within 6 feet of lightning protection conductors may have to be bonded to those conductors (to eliminate arcing between). An example would be a rooftop mounted air conditioning compressor/condenser unit. It would seem like bonding will route the lightning currents into the building systems, and it will. But not bonding can result in an arc between systems which can produce more damage. .

Not bonding the building ground to the lightning system ground is likely to be a far bigger disaster. The ideal is that the building electrical systems would float up with the rod system and there would be no damage, like a bird sitting on a high voltage wire.

When the building ground floats up thousands of volts, it floats away from the power hot conductors, in effect producing a surge on the power service wires. NFPA 780 requires a power service surge suppressor. The suppressor brings the hot wires near the system ground. (That results in sending some of the surge out on the power hot and neutral service wires. Similarly when the phone and cable entry protectors are pulled up by their system ground connection, they will send some lf the surge out on the phone and cable wires.)

There are some holes in the "bird on the high voltage wire".

- The voltage at earth mounted equipment, like a pad mounted A/C compressor/condenser can be far different from the building system ground. Surge protection may be necessary at the unit (this is in the IEEE guide).

- Building wiring can act as an antenna and pick energy from a near strike or downconductors (covered a bit in the NIST guide.) An example is alarm wires forming a long-wire antenna. Protection should be provided by the manufacturer. Another example would be power and cable wires forming a loop antenna with loop closed at the power ground - cable entry connection and the loop connected to a TV. A plug-in suppressor should be effective.

If I was having rods (actually they are =93air terminals=94 now) I would make sure the installer was competent and followed NFPA 780.

alt.home.repair ?might? have some people who have rod systems on their houses.

-- bud--

If surge current is not earthed before entering a building, then wires and connected equipment may be at 5000 volts above earth ground (8000+ volts destroyed on Page 42 Figure 8).

However proper earthing (single point earthing) of that current at the service entrance means an both ground rod and earth beneath the house rise to thousands of volts (relative to distant earthborn charges). Same voltage. Since same thousands of volts are beneath the building, then no massive voltage exists between AC wires and earth below. No massive voltage exists destructively across appliances (or humans).

Equipotential is the concept. If a surge has no or insufficient earthing, then the appliance may be 8000 volts different from basement floor, air ducts, or linoleum floor. But with single point earthing, an appliance at 8000 volts is same voltage as the basement floor. Therefore no destructive voltage across any appliance.

Equipotential is easily achieved in conductive soils. In places where soil is less conductive (ie Florida), homes are now constructed with even better earthing - Ufer grounds - so that equipotential still exists:

Plug-in protectors cannot provide the equipotential which is so essential for protection. Where soil makes equipotential difficult, the single point earth ground is enlarged to include a building's footings. Protection is only as effective as its earth ground. Equipotential means earth voltage beneath the entire building increases equally so that no destructive voltages exist inside a building: This single point earth ground concept and equipotential are why direct lightning strikes to munitions buildings cause no explosion. Ufer grounds, so often used where no electronics damage can result, was pioneered in munitions storage facilities. Why no damage? A single point earth ground means equipotential exists beneath and across munitions. Everything can rise to thousands of volts. Single point earthing means everything rises equally - no hazardous voltages exist inside the structure.

Both meeting and exceeding post 1990 code requirements is required for surge protection. Having no damage (having equipotential) is why telcos use earthed =91whole house=92 protectors and waste no money on plug- in protectors.

Properly earthed surges to protect electronics also means better human protection. Protection that exceeds what is required by code.

I stand corrected, not only IEEE engineers miss the effects of the real world but some of the writers on this NG as well.. Next panel I find with popped MOV's, I'll just tell it " that 'w_tom' said its not so " cause it was bonded to all the other grounds in the building and to get back to work protecting the equipment. :o)

"w_tom" wrote

. Assume the building is earthed with a single ground rod w_ mentions above. Assume the resistance to earth is 10 ohms which is excellent in general and a miracle for a ground rod. And that a surge results in a current to earth of 1000A The voltage at the building 'ground' will be

10,000V above absolute earth potential.

As a rule of thumb 70% of the voltage drop in the ground away from a ground rod is in the first 3 feet. That means from the building =91ground=92 to earth more than 3 feet from the rod there will be at least

7,000V.

Not same voltage. .

Single point earthing means only that all 'grounds' (power, phone, cable, ...) are connected at a single point (or single system). That does not make the all the earth below the house at the same potential.

If the connecting wires are *short* it does make the ground references for all systems the same so there is not high voltage between power and phone and cable wires. The author of the NIST guide says "the impedance of the grounding system to 'true earth' is far less important than the integrity of the bonding of the various parts of the grounding system." A significant part of protection is the =93bird on the high voltage wire=94. .

. Nonsense.

In the ground rod example, if the soil near the rod is more conductive then the soil further from the rod is more conductive. You still get

70% of the voltage drop in the first 3 feet from the rod. .

. New construction usually requires installing a "concrete encased electrode" which is a wire or rebar in a concrete footing. This will not insure equipotential under the house unless the rebar is tied all around the house or the wire is extended around the house. .

The Ufer ground tested in munitions buildings tied all of the footing rebar and all of the floor rebar into a single connected system. The NEC "concrete encased electrode" is commonly called a Ufer ground, but is not nearly as extensive.

You can bet you don't have equipotential under your house.

-- bud--

Tom, Bud, Rocky -- you folks have given me a wealth of information in response to my questions! I've read everything, and so far accessed most of the links. This is going to take a good bit of study for me, but I promise that I WILL do it!

In the meantime, may I offer what I believe is a significant fact? There is a common thread leading through the recent discussions: Embedded electrode (Ufer) grounds.

IMHO, construction here in NE Thailand should lend itself very amenably to this kind of grounding. And fortuitously, I have not yet even begun the foundation for my construction.

To explain: Buildings here are constructed of virtually 90% rebar reinforced concrete(*) -- pilings, footings, columns, cross-beams. And the rebar is all tightly wired together at each stage before the concrete is poured. The roof frame is then constructed of channel iron, that is welded to the rebar that protrudes out of the top of the topmost columns. So what we end up with, IMHO, is a whole structure that is Ufer grounded.

This leads me to a few observations, (based upon what I have learned from you all in this thread):

1) Lightning rods, (air terminals), if installed, might just as well be welded to the channel iron in the roof frame, instead of, (or maybe in addition to) the down conductors to their respective grounding rods.

2) A common "single point" ground point can be selected almost anywhere, as long as that point is assuredly VERY well part of the overall Ufer/system ground. And that same point should be used for grounding all services, as well as the alarm panel.

3) And the scary observation: Since the house will now become a large high voltage "cage" if there is a close by or direct lightning hit, then all of the electrical wiring, including the sensor wires for the alarm system, will now become antennas that will attract arcing or inductive surge loadings.

This is as far as I have gotten. Is my thinking on track? Please amplify and correct me where I am wrong.

Thank you again for all of your insights! Now I will return to studying what you have already provided.

(*) For accuracy, the remaining 10%, (well, maybe 15-20%), is composed of filler bricks, ceramic roofing tiles, and a modest amount of wood -- but I assume this is irrelevant to the present discussion.

I would not intentionally introduce a lightning path into the framing. It may be a good idea, but it is not obvious to me that it is. .

. If I was guessing where you were Thailand would not have been one of the guesses. Electrical code requirements may be different from what I have said..

In the US the "single point" is near the power service because the neutral and ground are tied together at that point and it is the ground reference for the power system. Phone and cable are more flexible in location. Phone and cable entry protectors should be near the power service with a *short* 'ground' wire to the ground at the power service. If the neutral and ground are not bonded, the magic point would be where a power service suppressor is. The "single point" must be tied to earth, preferably with a short conductor. But a short wire between systems is more important than a short conductor to earth.

"Concrete encased electrodes" were probably added to the NEC because they are relatively easy to add and are far better than a ground rod. They would be the "supplemental" electrode for a water pipe. .

. Arcing would only be if the rods were hit and only to metal 'near' the rod system.

Pickup from antenna effect should only be a problem for very close hits. There is not much energy, but it goes to terminals that *may* not be protected. The alarm guys should have an idea how well protected the alarm loop terminals are. Wireless alarms avoid the wires (but are the antennas protected?)

The major hazard is from is from surges entering on power/phone/cable wires (or direct strike).

A good contractor that installs lightning protection systems should know what to do.

-- bud--

Let's says lightning strikes nearby to a 100 meter antenna. An antenna designed to receive RF energy would be easily most affected by fields from that nearby strike. Experiments confirm that antenna without a load could be thousands of volts. Then we attach an NE-2 glow light (also found inside lighted switches) from each antenna lead to earth ground. Now that thousands of volts, conducting milliamps to earth by a neon glow lamp, is reduced to only tens of volts. Many will hear about the thousands of volts. But never learn how thousands of volts is made irrelevant even by an NE-2 glow light.

In another event, lightning struck a building's lightning rod. Earth connection was only four feet away from a PC. If fields from a direct lightning strike were so destructive, then lightning currents on a nearby wire will harm the PC? No. Software did not even crash. The fields are easily made irrelevant with simple protection also found in every cell phone and automobile car radio.

Don't worry about fields from a nearby strike. Such 'damage' is promoted by myths and speculation. Protection is about diverting a direct strike harmlessly in earth. The direct strike is made irrelevant when energy is dissipated harmlessly in earth and gets there without passing inside the building. Its fields are easily made irrelevant.

Better protection means all grounding wires must remain separate until they all meet as the single point ground. Best is to ground lightning rods separately from the building structure so that building and lightning rods meet AT common ground. One reason why: no conductors are perfect. If lightning uses a building structure, then voltage differences can exists between floors. If lightning currents bypass the building, than all floors (conducting no current) remain at the same potential as the earth ground.

Connecting lightning rods to a building's structure typically would not cause damage. But a lightning strike may cause interruptions on internal data cabling. Better to earth lightning rods by a separate and dedicated connection - not via the building. An IEEE paper by Montandon and Rubinstein in Transactions on Electromagnetic Compatibility on 5 Nov 1998 further describes these whys. Their conclusions include: