Comcast cable grounding/bonding

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Old 09-09-18, 01:32 PM
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Comcast cable grounding/bonding

Hello,
How do I check for proper grounding/bonding on my comcast cable line? I have a multimeter but have come across a few threads with people warning about damaging equipment, self, etc. So I could use some detailed guidance on how to check this.

Here is the background of my situation: After a bit of investigating and research, Iíve discovered what I think is the cause of two incidents of HDMI component failures (both after thunderstorms) on my TV, cable box and home theater receiver. I found that my plumbing system does not appear to be properly bonded/grounded due to a new section of Pex piping that was installed in between the main water line IN ground near my electrical box and the rest of the houseís copper plumbing. The coax cable line has a proper green ground wire attached at the outside of my house where it then comes in to the house and is clamped to a water pipe in my house. But again, it is after the Pex at the other end of the house.

So Iím looking for a way to verify the condition with my multimeter before and after I extend the house ground to the plumbing again.

Side note, I donít have any signal/quality issues with the cable. Thanks in advance.
 
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Old 09-09-18, 01:41 PM
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Welcome to the forums.

The coax cable line has a proper green ground wire attached at the outside of my house where it then comes in to the house and is clamped to a water pipe in my house.
That is not a proper grounding method. That is a utilities quickie method.

The proper cable ground is a ground block on the outside of the house and then a ground wire to the electric grounding system. Many utilities use clamps that clamp to the meter pan or the ground wire to the panel..... if there is one.
 
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Old 09-09-18, 02:56 PM
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Comcast Cable Grounding/Bonding

Thanks Pete. I seeÖwell, I read a couple of other guys say that this is what it might look likeÖOk. So is this a grounding block as seen in the picture I attached? Is the not proper part that the ground should run all the way back to the main water line IN ground that's connected to my electrical panel, or to the panel itself?
 
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Old 09-09-18, 03:49 PM
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For cable and phone line grounding to the water pipe is acceptable so long as it is continuous metallic pipe all the way to point of entrance (where main shutoff would be) and it is properly grounded to the grounding block of the main panel or grounding rod.
 
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Old 09-09-18, 04:14 PM
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How do I check...

Ok thanks. So can anyone tell me how I can verify the no ground/ground before and after with my multimeter? Iíd like to learn something and be sure that the change produces the expected result. Thanks!
 
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Old 09-09-18, 04:20 PM
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Measure resistance between ground of your coax and ground of any outlets in your house. It should read near 0.
 
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Old 09-09-18, 04:29 PM
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If that cable drop is near the meter pan..... measure to there for ground.
 
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Old 09-09-18, 05:54 PM
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Ok, I just want to confirm (sorry for the novice questions), Iíll use the ohm/resistance setting on my multimeter and put one probe on the coax ground wire (or outer part of coax connector?) and one on a nearby known good outlet ground, and expect it will read open as it is now but should be zero once I ground it right?

Is there any risk to any components, etc. by using the multimeter in this situation? Anything I should disconnect? Iíd read a couple folks mention some potential with this but not sure if it applies here. Thanks everyone!
 
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Old 09-09-18, 07:20 PM
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Since you are measuring something that could possibly have a voltage on it..... check for voltage with the meter in the AC volt scale first. You should measure 0 volts. If you see any voltage there..... the cable line is not grounded.

If you see no voltage..... switch your meter to auto OHMS or Rx1 if you have that setting. You should measure very close to 0 ohms. Technically you should measure whatever you see when you short the two probes together.
 
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Old 09-10-18, 06:55 AM
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Proper grounding is better measured using a load current as opposed to an ohmmeter (continuity tester; multimeter).

This requires electrical work dexterity and know how.

I would use a hair dryer although some experts would say a 100 watt incandescent lamp (bulb) is sufficient.

Using wires with alligator clips on the ends connect one prong of the test device (e.g. table lamp fixture) plug to the hot slot of a nearby receptacle. Connect the other flat plug prong to the place you expect to be or need to be grounded. Also set the meter to AC volts and then connect meter probes to those same points.

Turn on the device. just for a moment. If the voltage as measured dips noticeably below 120 then you do not have a good solid ground path from the grounding point you are trying to verify.

An alternative to measuring is to inspect the grounding path. Start with the grounding electrode conductor, a fat wire running from the main panel (panel or box with first whole house disconnecting means) neutral bar over to a ground rod or to a water pipe. (At the main panel the neutral bar and ground bar, if separate items, are connected to each other.) The grounding (an equipment grounding conductor) for the coax or antenna is properly connected somewhere along this GEC (fat wire). The far end of the EGC (may be multiple lengths of wire spliced end to end) for the coax is connected to the coax plug or to the jack shell of the equipment that the coax plug is attached to.

To me the importance of bonding (to your house electrical ground ) the incoming cable from a cable TV provider is to protect your equipment from wiring problems or defects or equipment failures of the provider's equipment which may up on the utility pole.
 

Last edited by AllanJ; 09-10-18 at 07:11 AM.
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Old 09-17-18, 05:40 PM
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Ok, Iím kind of frustrated now but maybe someone can help draw a conclusion from my testing. I disconnected the main cable coming into the house from the first connection.

I tested for voltage with my multimeter by touching one probe to the coax center wire and the other probe on the outer sheilding/screw. The reading jumped around a bit but I came up with .335. This should indicate itís not grounded, correct?

Then I checked for resistance by touching one probe to a known good outlet ground and the other to the outer part of the coax connector. The values jumped all over the place from .46 - 8.6. I donít know what to make of it since I thought I would either get 0 ohms (grounded) or OPEN/O.L (not grounded.

Any thoughts? Thanks.
 
 

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