Earth ground serves many functions. It is for human safety. National Electrical Code is concerned with human safety. NEC demands that cable and AC electric share a common earthing electrode. It even states a maximum connection length to that earthing electrode.
Then earthing also addresses lightning protection. For lightning, the installation must also do things that exceed what NEC demands. For example no sharp bends in the earthing wire, no splices, no bundled or adjacent to other earthing wires, not through metallic conduit, etc. And also for lightning, all earth utilities (AC electric, cable, satellite dish, and telephone) must be earthed to the same electrode.
Cinergy even demonstrates how to do this when somebody screws up - brings all utilities in at separate locations:
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Good news is that cable companies are finally telling installers to earth - also for lightning. Previously, cable installations were some of the worst examples of professionalism ever seen. But the earthing must include each and every incoming utility. The earth wire must be short - 10 feet or less. And that earthing is necessary for both transistor protection (lightning) and for human protection (NEC).
Chances are it's not your wiring and there's something wrong with at the cable company or with their equipment. Here's a summary of the problems I've encountered in the last few years:
I had a cousin who had a DSL problem. Her ISP said it was her computer. I told her it wasn't and she probably had a bad modem. The problem went on for weeks while they were giving her the run around. Finally she called them and told them she was canceling her account. They came to her house and replaced the modem and everything was fine.
I have an ex-son-in-law who's been going round and round with his cable company for weeks because his television only worked good sometimes--mostly at night. Actually, he had the same problem several months before that and a serviceman had fixed it. Anyway they had him trying everything and changing cables and promising someone would come out, etc. When the serviceman finally arrived, he told him the problem was because he was using RG-59 instead of RG-62, but actually it turned out the signal coming into his apartment was too weak.
I used to have DSL and came home one day from my daughter's house after a huge thunderstorm--one of the worst ones I've ever seen. Fortunately, everything still worked because now days most equipment has built-in surge protection. Everything still worked, that is, except my DSL connection. Upon taking a close look at the modem, I noticed it lacked a "CE" mark and, therefore, probably didn't have good surge protection. My ISP had me jumping through hoops for 3 weeks talking to their service center in India. Finally, a guy came out and replaced the modem. By then, though, I was so damned mad I canceled the service and went with a fiber optic connection. I had to buy my own modem, but they gave me a recommended model number (a Wireless - B Linksys).
Everything worked fine for a couple of weeks until I decided to download some music from Napster. Then I would always get disconnected for some mysterious reason. I called my ISP and they told me to call Napster. I did and Napster told me to contact my ISP (again). After that my ISP ran some tests and said everything was fine, but of course it wasn't. Finally, on about my 4th call a guy asked me what kind of Modem I had and then told me I needed to switch to a Wireless - G Linksys. That solved the problem.
820.100-B covers the earthing electrode to be used. Required connections are all to the power system grounding electrode system including the grounding electrode conductor, or points immediately adjacent.
820.100-A-4 requires the connection from the CATV ground block to the power electrode system above to be 20 feet or less.
An exception to 820.100-A-4 - for 1 and 2 family dwellings only - allows a separate rod to be used if the connection above cannot be made in 20 feet. But it requires bonding the CATV rod to the electrodes in 100-B above with a #6 or larger wire.
The NEC requires all grounding systems to be bonded together. That includes phone and lightning rods. I am not aware of any exceptions.
The IEEE published an excellent guide on surges and surge protection available at:
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on guide page 31 is an illustration of the problems if the wire from CATV ground block to power system electrode is too long. If the ground block had been connected only to a rod, and not bonded to the power system, the problem would have been much worse. As an approximation about 70% of the voltage drop from a rod to ?absolute earth potential? occurs in the first 3 feet from the rod. If earthing a lightning surge, the CATV rod would be at a far higher potential than the power system earthing point. And if the power system was earthed only at a rod, and the power system earthed a lightning surge, the power system would be at a far higher potential than the CATV earthing point.
Ground rods at different points are not necessarily at the same potential. And with "shale a few feet down" all the earthing is suspect. Bonding the systems puts them at the same potential.
You seem to be the only person convinced it is not a cable problem.
The cable installation is concerned with human safety from a lightning strike point of view.
Note that most cable modems as well as most set top cable converters are only two conductor fed devices, and no safety wire/fault return exists. for them.
On Thu, 04 Jan 2007 10:50:54 -0600, Bud-- Gave us:
I do not dispute your references at all. All I stated was that was what our employer required us to do. His inspectors even sent us back to sights which failed their inspections.
We had several at the pitch of three story or greater apartment buildings that were as long as the building is tall.
We were post wiring 12 to 50 unit structures.
This is all well and good, but does not change the fact of what they had us doing. I am sure they have modified their practices since
1979 though.
Cool.
I do not disagree.
I totally agree. Asshole installers from all involved walks of life cut corners when the real work requisite faces them.
No shirt Shitlock.
I watched my cable internet speed drop overnight after a cable installer "worked" inside our lockbox.
The original installer said my signal was GREAT. and my cable speed reflected that 7Mb/s in and 0.5 out. After the "phone guy" changed out the port taps in our lock box, I got 5Mb/s in, and was getting failures on outgoing packets. I am sure the signal strength has dropped, and would bet so. Now, it likely has spurs.
To this day it has never been the same, but Cox did "upgrade us all", and now I get 10Mb/s in and my old 0.5 out, but it still hiccups a lot on the out side, which is an ATM link, differing from the incoming transport mechanism.
So I have seen where the cable co can screw up even one's "digital reception" for one's internet link by no more than a few poorly cut fittings.
His problems, however, do point toward a house wiring issue, and other did have the same feeling. Sure it is quite possible that it is the cable co, but if they come out and read his attenuation level at his end of line, and it is OK, then it is NOT the cable co. It COULD be the cable modem.
In the neighborhood, phones started ringing constantly. Fire and utilities were called. One house suffered a neutral wire failure. Utilities were not properly earthed. So the house sought other grounding paths. One house had cable not properly earthed at its service entrance. Electric company emergency responder borrowed IR vision from the fire department. He could see coax cable inside walls red hot. Why? Had the cable been earthed at service entrance, then cable inside house would not be used to ground the first house. Missing earth ground almost meant a fire in the second house. Fortunately, that same missing ground caused phones to ring constantly. Example is earthing for human safety.
NEC only defines lightning protection in human threat terms. NEC does not care if lightning protection works or does not. NEC does not address transistor safety. But your cable must be earthed so that humans are not electrocuted AND so that transistors are protected. Those are two separate functions - earthing to protect both humans and transistors from many different electrical sources.
Many installers don't understand the concept. Earthing sufficient for human safety would not be sufficient for transistors safety. Therefore we earth to meet post 1990 NEC requirements. Then we enhance that earthing also for lighthning protection. No earth ground means no lightning protection. But earthing does more than lightning protection.
Cable box, etc must not be safety grounded by the cable. A cable box safety grounded by its cable is a threat to human safety. TV and cable box should even contain galvanic isolation as part of what some call 'double insulated'. Just another reason why cable cannot 'bond' the TV or cable box.
If OP had a neutral wire problem, then he has light bulbs clearly changing intensity as major appliances power on and off. But again I am posting what was apparently ignored. There is nothing in that OP's posts to suggest a neutral wire problem. There is plenty to suggest the earthing is not properly installed and that other internal wire problems exist. Provided were measurements to find that failure. The OP never posted back.
. Meanwhile, learn various reasons for grounding all utilities to a common earthing point. Human safety. Transistor safety. Even eliminates ground loops and other noise in electronics. Multiple functions using the same wire.
Scary is that you believe cable wire is acceptable for safety ground to a cable box. Absolutely not. Reas> On 3 Jan 2007 21:27:07 -0800, "w_tom" Gave us:
Why I even respond to a retarded top posting Usenet twit, I'll never know. If you know so much about convention, learn one!
You're nuts. Phones ring when RING TONES get sent onto their line.
CITE a red hot IR cable story that has photos, jerk. Don't just create a "possible" scenario.
No shit.
Those are not all the reasons, but you are close.
No shit? Personnel... equipment...
Were it not for you, I'd have never known.... Sure, bub.
It had nothing to do with concept. It was our installation policy.
You're not too bright. 40 mA on the skin, across the chest can cause fibrillation. Only 10 mA into puncture wounds (through our very salty conductive blood), and only 2 mA directly applied to the heart in open heart surgery procedures.
With P-N junctions (doesn'y have anything to do with transistors per se) the determining factor is voltage, not current. When the voltage reaches a point where the junction interface gets breached failure occurs, or damage is induced at the site that causes failure in the future far sooner than a non-assaulted junction.
The installations I remarked on were, as stated, back in the late seventies. I also stated that I was quite sure that their policy had likely since changed.
As it relates to power, yes. As it relates to those comm lines, however, the main purpose is the lightning protection, and that protection is for both humans and equipment.
Not in the proper setting, but in a household setting with all the typical associated gear, sure. All hypothetical though since no cable boxes are made with fault lines. My early cable modems may have been, however. I am not talking about the store bought variety after the spec passed either.
Not if he uses fluorescent replacements everywhere.
What is actually suggested is that he may be using a sad meter, making an improperly setup measurement.
He needs an electrician to inspect his service panel, and ideally, load test each branch to identify any anomalies, and more easily pinpoint the source location.
I suspect methodology errors at this point.
I don't need to learn it. I was merely iterating what that company's policy is/was.
A terminology in common use.
A never used term.
I've built HV supplies that have 0.0006% ripple. I know how to ground circuits. From the very smallest pico amp leakage intolerant PMT supplies, to the 180kV X-Ray driver in use at all the airports.
Watch out, you are getting loopy.
Show me where I said that.
I no longer perform cable installations. That was decades ago. I am sure installers today are far better trained as there are more in house personnel than contract installers in some systems.
With the previous post below, all I can do is close by calling you the utter TOFU retard that you are.
Snipped TOFU from the TOFU retard. Get a clue Tom.
Joe Your position reveals a failure to train and supervise on the part of Warner Amex CUBE system. The National Electric Code and all of the local codes that are based on it requires that separate grounding electrodes be bonded together into a single grounding electrode system. Cable installers working on buildings rather than poles or hand holes are not exempt from that requirement. Every one of those separate rods is a destructive surge path waiting to happen.
On Sat, 06 Jan 2007 22:15:29 GMT Thomas D. Horne, FF EMT wrote: | JoeBloe wrote: |> On Wed, 03 Jan 2007 14:24:15 -0600, Bud-- |> Gave us: |> |>> Verify that the ground block at the cable entry is connected to the |>> grounding system for the power. It can't (in the US) just be connected |>> to its own ground rod. |> |> |> Not true. We were REQUIRED to drive OUR OWN 8 ft rod whenever we |> did a post wire on an apartment complex. |> |> This was Time Warner (Warner Amex CUBE system at the time) |> |> Single home drops MAY be attached at the house tie point, or a ground |> rod CAN be driven. It is for lightning protection, and the problems |> being discussed in this thread are not related to that. |> |> That alone points toward the issue being with HIS power wiring, and |> NOT the cable system. | | Joe | Your position reveals a failure to train and supervise on the part of | Warner Amex CUBE system. The National Electric Code and all of the | local codes that are based on it requires that separate grounding | electrodes be bonded together into a single grounding electrode system. | Cable installers working on buildings rather than poles or hand holes | are not exempt from that requirement. Every one of those separate rods | is a destructive surge path waiting to happen.
I Agree 100% with Tom's position. I also have to admit that despite so many other failures and lack of training among Comcast technicians or their managers, and the company in general, this (connecting all the ground rods solidly together) happens to be one thing they got right. The previous cable system operator here didn't do it right, and that's one of the things Comcast is working on now, for almost the entire system, re-wiring every home to get the grounding correct. They are just not putting enough manpower into it. But at least they know how it's supposed to be wired.
On Sat, 06 Jan 2007 22:15:29 GMT, "Thomas D. Horne, FF EMT" Gave us:
No. That IS what was being trained at the time, and they even went out with installation auditors and ultrasounded the rods to make sure no installers were cutting them off. That was 1979.
In most places in the US the neutral is grounded at the transformer. Even if that particular "ground" ain't so hot, the neutral for the primary side provides a connections to other grounds.
If the neutral is bonded to the house ground I just don't see more than, say, 5 volts difference between "grounds" and certainly not even close to 10 volts.
The neutral might actually be broken and the "bonding" is providing the neutral current. If the only L-N loads are relatively light, the unbalance might not be noticed.
If the OP has a VOM, he should measure the L1-N, L2-N, L1-G, L2-G, and N-G voltages while switching on and off a solid 10 amp load like a toaster. The results should give a pretty good idea of where the problem lies.
On Sun, 7 Jan 2007 21:29:23 -0500, "John Gilmer" Gave us:
Every telephone pole I ever saw had the big #10 Ga minimum bare solid copper strand in a groove cut down the face of the pole, Some were insulated wire, but ALL were tied to a grounding rod sank right at the base of the pole.
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