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>>> Coax Surge Protection <<<

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ShiningBengal is offline Old Post 06-28-2004 06:49 PM
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ShiningBengal
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Registered: Mar 2001
Location: Minneapolis, MN USA
Posts: 441

quote:
Originally posted by aaronwt
It is grounded by the power meters. All the utilites are in the same location(within 3 feet) The meters are using the same grounding rod as the other utilites. I am connected to the same grounding rod.

Anyway it's been like this for 2.5 years and I don't have any problems, so I see no need to change it now.



How do you connect a ground "to the power meters?" And if you did this, how do you know they are at the same ground potential as the main service entrance? Are you saying the meter bank is connected to a ground rod, and you have somehow connected your ground to the meter bank? You can't get inside the meter enclosure--they are sealed by the utility. An you can't legally ground anything to the utility's equipment.

In this part of the country, a ground rod is almost NEVER used as a main system ground. They are notoriously unreliable as a system ground. Utilities use ground rods to ground their equipment because they do not usually have access to a water main to do this.

They only time they are permitted is if there is no other way to ground equipment. The water main is used 99.5% of the time, with the water meter jumpered to maintain the ground if the meter is removed for any reason.

These are the facts:

1. Ground loops are responsible for the vast majority of noise on CATV, cable, and other coaxial feeds to A/V equipment. The video noise is usually characterized by horizontal lines moving slowly up or down the screen.

2. Shielding on coaxial cable running a short distance past line voltage equipment will prevent the cable from picking up interference if it is grounded to a system ground.

3. If you have a ground loop, if the coax is grounded at any point to a system ground (i.e., through a 3-prong grounded plug at a wall outlet), it will eliminate the ground loop.

4. Surge protectors will not eliminate the effects of a ground loop. A good ground will.

I can understand your not wanting to spend time sorting this issue out for yourself, since you have eliminated the source of the interference. But for others, you should ALWAYS suspect a ground loop when you get video interference in your satellite system.

The best way to deal with a ground loop---assuming you have a grounded main service entrance---is to eliminate it with proper ground wiring.

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aaronwt is offline Old Post 06-28-2004 06:59 PM
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aaronwt
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Registered: Jan 2002
Location: Northern VA(Woodbridge)
Posts: 803

The water mains are on the opposite side of the building. A large guage ground wire comes from the electric meters and goes to the grounding rod. The other utilities are also connected to this ground rod. The building is 20 years old if that makes a difference. I have no idea what the codes were like then or even if they were followed. I know there was alot of corruption in this area in the late 80's with the inspectors(the county to the North). I have first hand knowledge of several instances of contractors paying off inspectors to get them to pass inspections.

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ShiningBengal is offline Old Post 06-28-2004 07:31 PM
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ShiningBengal
Curmudgeon Emeritus

Registered: Mar 2001
Location: Minneapolis, MN USA
Posts: 441

quote:
Originally posted by aaronwt
The water mains are on the opposite side of the building. A large guage ground wire comes from the electric meters and goes to the grounding rod. The other utilities are also connected to this ground rod. The building is 20 years old if that makes a difference. I have no idea what the codes were like then or even if they were followed. I know there was alot of corruption in this area in the late 80's with the inspectors(the county to the North). I have first hand knowledge of several instances of contractors paying off inspectors to get them to pass inspections.


What your are describing is multiple building grounds. This is exactly what causes ground loops, and why good wiring practice (as well as the National Electrical Code) doesn't permit this.

Most likely, the utility didn't want to spend the bucks to run a ground wire around the building to the other side (they can't run it inside the building for more than a very short distance.)

Your unwitting "work around" of eliminating the ground loop by grounding it through the wall outlet is effective in stopping the noise because you have established a pathway from the coax shield to the building system ground.

But you haven't (at least legally) grounded your coaxial cable. If for some reason, you unplug your surge protector from the wall, you break the ground. This can be dangerous under certain conditions, but I wouldn't lose any sleep over it.

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greywolf is offline Old Post 06-28-2004 08:35 PM
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greywolf
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Registered: Apr 2004
Location: Evanston IL
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The NEC says "The grounding conductor shall be connected to the nearest accessible location as follows: (a)The building or structure electrode system as covered in 250-50. (b)The grounded interior metal water piping system as covered in 250-104 (a). (c)The power service accessible means external to enclosures as covered in Section 250-92 (b). (d)The metallic power service raceway. (e)The service equipment enclosure, or (f)The grounding electrode conductor or the grounding electrode conductor metal enclosures."

The meter enclosure, as part of the raceway, being bonded to the main building ground rod is typical and good practice. It can cause problems in very dry areas though and the longer the ground rod, the better. Using the water main as a ground rod can have its own problems with the advent of plastic pipe or the pipe run being shallow. The 2002 NEC adds that, if the water pipe is used for ground, it must be all metal and the equipment ground wire must be connected to the pipe within 5ft of the pipes entry to the building. The electrical service panel must also be bonded within that 5 ft.

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ShiningBengal is offline Old Post 06-28-2004 09:22 PM
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ShiningBengal
Curmudgeon Emeritus

Registered: Mar 2001
Location: Minneapolis, MN USA
Posts: 441

quote:
Originally posted by greywolf
The NEC says "The grounding conductor shall be connected to the nearest accessible location as follows: (a)The building or structure electrode system as covered in 250-50. (b)The grounded interior metal water piping system as covered in 250-104 (a). (c)The power service accessible means external to enclosures as covered in Section 250-92 (b). (d)The metallic power service raceway. (e)The service equipment enclosure, or (f)The grounding electrode conductor or the grounding electrode conductor metal enclosures."

The meter enclosure, as part of the raceway, being bonded to the main building ground rod is typical and good practice. It can cause problems in very dry areas though and the longer the ground rod, the better. Using the water main as a ground rod can have its own problems with the advent of plastic pipe or the pipe run being shallow. The 2002 NEC adds that, if the water pipe is used for ground, it must be all metal and the equipment ground wire must be connected to the pipe within 5ft of the pipes entry to the building. The electrical service panel must also be bonded within that 5 ft.



You are correct that the water supply can have "its own problems." However, it is difficult to imagine the use of PVC as a water main for an apartment building. I've never seen such a thing. Of course, in Minnesota, water pipes are never run shallow, as they must be safely below the frost line. Larger mains are typically cast iron and smaller ones copper. Maybe they polyethelene tubing in Virginia. But if there is a problem getting a good ground with a water main that may run hundreds of feet underground, how can it be possible to get a good ground with a ground rod which is typically 8 to 10 feet? Builders often use really poor soil to backfill a building, and this can exacerbate the problem.

You can also install a ground rod today and have a very reliable ground and come back 10 years later and have a poor one.

As you mention, the effectiveness of a driven ground rod is highly variable, not just with the depth, but the soil conditions, and moisture content (which also varies independently).

Utilities do not have to abide by the same rules as contractors do. If the apartment building were in Minnesota, the contractor would almost certainly locate the service entrance near the water main. If possible, the ground would be connected on the street side of the meter, and if not, the meter would be jumpered with the appropriate guage grounding conductor.

Who knows what was done in this case?

The main issue with ground loops, however, is not the quality of the ground, but whether or not there is a single grounding point to which all secondary grounds are bonded.

Perhaps there is only one ground here, but the present case sure sounds like a ground loop related issue. I can't think of any other possibility given that attaching the coax to a grounded device seems to cure it.

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rcawood is offline Old Post 06-28-2004 11:47 PM
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Well I ran my new cable runs yesterday. Going through the Panamax surge protector marked "cable" resulted in no satellite signal. I connected directly and had no problem.

I'm going to try again to see if this was just a fluke/timing. However it looks like I need to get a surge protector for just two runs of RG6 (don't need outlets or minimal outlets). The primary reason I use a surge protector is the "insurance". Therefore I believe I need everything running through a surge protector.

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aaronwt is offline Old Post 06-29-2004 05:53 AM
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aaronwt
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The pipes in these condos are not metal. The main line going to the water meter for the building isn't metal either.

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aaronwt is offline Old Post 06-29-2004 05:56 AM
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aaronwt
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quote:
Originally posted by rcawood
Well I ran my new cable runs yesterday. Going through the Panamax surge protector marked "cable" resulted in no satellite signal. I connected directly and had no problem.

I'm going to try again to see if this was just a fluke/timing. However it looks like I need to get a surge protector for just two runs of RG6 (don't need outlets or minimal outlets). The primary reason I use a surge protector is the "insurance". Therefore I believe I need everything running through a surge protector.



If it is only rated for 1Ghz(like some are)it won't be able to pass the satellite signal. The monster coax surge protectors go up to at least 2Ghz, no matter what the label is on them(at least the models I have does)I had to verify this with Monster Cable before I bought them to make sure I wouldn't have any problems.

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ShiningBengal is offline Old Post 06-29-2004 07:15 AM
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ShiningBengal
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Registered: Mar 2001
Location: Minneapolis, MN USA
Posts: 441

quote:
Originally posted by aaronwt
The pipes in these condos are not metal. The main line going to the water meter for the building isn't metal either.


Holy horsepucky! I've heard of non-metallic water mains, but I hever thought anyone actually used them!

Seriously, though, regardless of where it originated, you almost certainly have a ground loop somewhere in your system.

A ground loop generates noise in A/V equipment by in effect, acting as both a coil and an antenna. The coil can pick up magnetic variations in power equipment--such as a tranformer, or even an air conditioning compressor. It can also act as an antenna, picking up radio frequency signals and amplifying them. The type of video noise you see on your monitor is very strong evidence of these signals being present within the ground loop.

With cable TV, or CATV systems, you can use an inline device called a "ground breaker" which introduces a small gap in the shield of the cable, breaking the current path but leaving the RF carrying capabilities intact. But you can't do that with satellite systems, since the cable must carry a DC voltage from the receiver back to the LNB to switch polarities as the receiver requires this to receive a particular channel. The gap in a ground breaker makes this impossible.

Just be glad you found a way to get rid of the effects. Ground loops can be very difficult to resolve satisfactorily.

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markp99 is offline Old Post 06-29-2004 07:20 AM
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Just got back from our local Atlas store. They are having a 2 for 1 sale on everything this week. Bought about $150 worth (x2!).

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