Coax grounding

[SGKent]

Pulling new coax for if we go to Comcast / Xfinity. Need guidance on grounding for lightning. We are in a suburb of Sacramento and don't see much but sometimes it happens around here.

Power, telephone/DSL, and gas come in on the N side of the house. Water on the W side, and Comcast on S side. 30 years ago when I had Comcast it came in on the S side, wrapped around to the E side and came in thru a hole in the wall/siding. They put a lightning arrestor on the outside and tied it to an aluminum patio cover. The patio cover is mounted to wood and concrete. No real grounding. I added a grounding rod for the spa that I used to have and tied the patio cover to that as well.

When the house was re-sided (T1-11) I moved the coax to inside the attic and added a lightning arrestor on the outside before the coax entered the attic, whether from Comcast/Xifinity, or an off the air antenna that I had at one time. That arrestor is grounded via a 10 ga grounding wire to a 8' rod in the ground on the S side of the house. It does not tie into the house wiring. The service entrance for electric is 50' way on the other side of the house. There are copper pipes in the wall near there but they run up and thru the attic. There is no house ground on that side of the house other than electrical plugs in the walls.

I am trying to figure how to properly ground the coax at the point of entry. Can I continue to use the 8' grounding bar with the 10 ga wire? Or do I need to tie into the house ground which I wonder how I would do that considering that service entrance is 70' away with the distance and drop. Also the main water entrance is a type of plastic pipe so I can't run a wire around the house 30' to that point to get a good ground. What do you electricians do in a situation like this?

 

[sberry]

Use the rod. I believe there is a limit as to how far they run to the electric ground. You do not want to tie this to plumbing or "invite" a strike in to the house.

 

[Terry D]

Code these days, at least that is what is required here, is to install a intersystem grounding bridge on the grounding electrode conductor which is connected to the ground rod and terminates in the meter base. All telephone , cable, satellite ground connections terminate here. The style shown glues onto PVC. They also make a style that will connect to the bare wire. Just Google intersystem ground bridge. I am not aware of any distance restrictions.


https://images.search.yahoo.com/sea...edia.co/media/images/GBB5P-3.jpg&action=click

 

[SGKent]

Terry doe the NEC recommend I run a grounding wire 70' thru the attic to reach the other side of the house where the service enters? My concern is the same as sberry - I don't want lightning tracking thru the attic or following copper pipes thru the attic. I want it staying outside the house. All the grounding wire is going to do in a large strike is provide a spot for the leader to follow, which then the main strike follows the length of the attic. This home was built in 1979 and the original coax installed about 1985.

View media item 103601

 

[slow]

my parents have an additional 150 feet of coax in the ground going from the right side of the house, to the electrical ground on the left and then back to the right side of the house where the coax originally entered the house. The cable company paid for this to be done many years ago including boring under the driveway

 

[SGKent]

my parents have an additional 150 feet of coax in the ground going from the right side of the house, to the electrical ground on the left and then back to the right side of the house where the coax originally entered the house. The cable company paid for this to be done many years ago including boring under the driveway

Here they won't even dig a trench to lay the cable deeper than an inch or two. Maybe if we were in an area like FL or the mid-west, mid-south where strikes were common they would. When they added the cable in 1985 they went between homes. It would have been better if they would have gone on the same side as the electrical service but they didn't. The phone system is next to the gas, and that is grounded to the gas line that goes into the ground. They didn't even clamp it - they just wrapped the wire around it a couple times. Both the phone and gas company have had a chance to fix that and they won't so the idea the Comcast will run an extra 150' of coax won't happen. The riser at the street is grounded so any strike would follow the coax into that riser and into the area the TV is. I'd like to provide a shorter more robust path to ground. We have lots of tall trees in the area so the risk is minimal but none the less exists.

 

[sberry]

I havnt read it in a while but I think if the electric is not 20 ft you can drive a rod. On new installs,, like Terryville said they now want a connector installed on the wire going to the rod so the other I stalled have a simple place to hook on, they used to allow a bug,,, a split bolt to hook there.
There is absolutely NO reason to super complicate this, it's a long was thru/around,,,, use the pounded rod. Un wire the phone from gas, go to a rod or electric rod if it's close enough, phone is 14 or better and it may even call for an insate wire,, I old ones with solid black 14. It's been a little since I read it,, might be article 880 ??? Gas is to be grounded to the electric, not to be used as a grounding electrode., should be done inside.

 

[ddawg16]

You want to use a coax ground block....it should be mounted where the coax enters the house. Run the ground wire down to it's own ground rod.

I personally would not attach the coax ground to any part of the house ground. Your big issue is someone else not properly grounding their coax...or the main line takes a hit....you want to the electrical surge to go to ground as soon as possible.

I have a dedicated ground rod just for my antenna and coax. If the coax takes a hit....it will take out the Cable modem....(replaceable). If the antenna takes a hit, it will take out the RF amp....(replaceable)

 

[kd3pc]

Keep in mind that lightning is not going to turn corners or go where your ground wire goes.

It is going to jump to GND at it's first and least resistive path. Which means that the coax shield that is vertical and heading towards the ground will become the path to ground.

No way would I run GND through the attic (or basement for that matter) or any further than is absolutely required. DDawg16 is on target.

 

[SGKent]

Well right now that is how I have it. The grounding block is on the side of the house where the cable comes to, and a heavy wire drops straight to a ground rod. Then I started research on it last night and the NEC code wants everything tied together. I can understand that from the logic of building a new house where the electrical paths are designed, but like you I don't want a lightning strike in the house, I want it to head right into the ground. So what if a few worms pop out of the ground..... I've been near lightning strikes and don't want one jumping from the attic thru the middle of the room to rebar in the concrete. That said - most people don't know but many types of rocks act as insulators. If for example you are in a granite cave and lightning hits nearby you are pretty much toast. The lightning sheets on granite, and you are the path from the top of the cave to the bottom of the cave. Lightning is best sent away from you, not towards you. So I don't want it traveling along a concrete floor either.

 

[SGKent]

I asked the head of the building dept here what he would do, he said he'd ask Comcast to decide what to do. The city doesn't have a preference on it. Since the Comcast contractors are the 22 year olds who dig 1" trenches for the cable, and who ground to a patio cover that is a floating ground, I think the ground rod that I have now is adequate but I will move it closer to the house if I can pull it, or drive a new one. We'll see on that. Thank you all for the suggestions.

 

[dave*99]

In addition to looking at grounding concerns - look at bonding concerns. There are requirements to bond the CATV coax to the service.

 

[SGKent]

In addition to looking at grounding concerns - look at bonding concerns. There are requirements to bond the CATV coax to the service.

That really should be Comcast's problem since the pedestal is theirs. Originally I installed the lightning arrestor / grounding block on the house below the mast in case the off air antenna on the chimney mount got struck. Lightning puts out feelers that become a leader, then the main strike follows the leader. By giving it a path from the antenna mast and coax to the ground, the leader should follow that. If we ever did get hit then it would fry the modem, but I am hoping that the path would be to ground thru that grounding wire and block. What travels back to Comcast on the cable is their problem to discharge. The same is true if the neighbor got hit and some of it ran down his coax, and came up my coax line, It should discharge to ground before coming into the house.

My main concern was if I was going to have to bond to the house service ground because I did not want to start running 70' of wire through the attic, or 130' or wire around the house and under concrete driveways etc.. As the photo shows, those services are all on the other side of the house.

When we have a rare electrical storm here we generally unplug sensitive electronic equipment during the storm. We had a doozy back about June 2011, or so where there was a static large cell about 500 yards behind us that threw a strike every 5 seconds or so for about an hour. Very unusual storm for here. Ironically it was the beginning of that awful drought.

View media item 103601

 

[Terry D]

Terry doe the NEC recommend I run a grounding wire 70' thru the attic to reach the other side of the house where the service enters? My concern is the same as sberry - I don't want lightning tracking thru the attic or following copper pipes thru the attic. I want it staying outside the house. All the grounding wire is going to do in a large strike is provide a spot for the leader to follow, which then the main strike follows the length of the attic. This home was built in 1979 and the original coax installed about 1985.

View media item 103601

This is how it is done now, they used to have goofy clamps that attached on the meter base and they are getting away from that. That ground rod outside is either your main ground or your supplemental ground. It is ok to ground all your systems to that. All you are doing is grounding the shield in the coax so it helps with interference getting induced. Where does the cable enter the house now. Is there a cable box on the outside

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[larry4406]

My current used house...

Comcast came in remote from the electric meter and its grounds. Prior owner or someone installed a ground rod remote at the cable entrance. This was not tied to the electric meter/house ground. Thus two separate grounds. This all unknown to me.

After we move in:

Thunder storm 1 fried my computer.

Thunder storm 2 fried all the HDMI inputs to my TV (cable TV)

After looking into both events, I discovered the isolated ground. I also was lucky and found that my house has a copper ground wire running from the electric panel thru the basement to the copper water piping. Using a split bolt I connected this grounding wire to the separate Comcast ground rod. Knock on wood the past 4 years have been event free whereas the first 2 let the smoke out of the TV and computer.

I am of the mindset that all need to be at the same potential.

Edit - See pattenp's Post 25. What I did is wrong by connecting the house grounding system to the auxiliary electrode. I will disconnect the house grounding system from the auxiliary electrode yet connect it to Comcast

 

[jeffmoss26]

use one of these. http://www.aifittings.com/catalog/grounding/intersystem-grounding-bridges/GB5

 

[larry4406]

use one of these. http://www.aifittings.com/catalog/grounding/intersystem-grounding-bridges/GB5

In our new construction homes we use these.

 

[sberry]

This ain't that fussy and no pixies live in the wires but the main reason they want it to connect together is so one doesn't have a better ground than another,, so your grounded equipment isn't better grounded than the cable. When there isn't a local method then they are allowed to drive another rod.

 

[dave*99]

That really should be Comcast's problem since the pedestal is theirs. Originally I installed the lightning arrestor / grounding block on the house below the mast in case the off air antenna on the chimney mount got struck. Lightning puts out feelers that become a leader, then the main strike follows the leader. By giving it a path from the antenna mast and coax to the ground, the leader should follow that. If we ever did get hit then it would fry the modem, but I am hoping that the path would be to ground thru that grounding wire and block. What travels back to Comcast on the cable is their problem to discharge. The same is true if the neighbor got hit and some of it ran down his coax, and came up my coax line, It should discharge to ground before coming into the house.

My main concern was if I was going to have to bond to the house service ground because I did not want to start running 70' of wire through the attic, or 130' or wire around the house and under concrete driveways etc.. As the photo shows, those services are all on the other side of the house.

When we have a rare electrical storm here we generally unplug sensitive electronic equipment during the storm. We had a doozy back about June 2011, or so where there was a static large cell about 500 yards behind us that threw a strike every 5 seconds or so for about an hour. Very unusual storm for here. Ironically it was the beginning of that awful drought.

View media item 103601

I understand your concerns about grounding in regards to lightning protection.
My comment about looking at bonding requirements is valid. Bonding of the CATV service is required because your house and your neighbors are electrically connected through the shield on the coax. If one of the houses has a bad service neutral, then neutral current can flow over the coax shield between houses.

 

[kd3pc]

I understand your concerns about grounding in regards to lightning protection.
My comment about looking at bonding requirements is valid. Bonding of the CATV service is required because your house and your neighbors are electrically connected through the shield on the coax. If one of the houses has a bad service neutral, then neutral current can flow over the coax shield between houses.

three things to look for as regards this....

grounded
grounding
bonding

all have a very specific meaning and task to complete, but it seems like so many words today - meaning is in the mind of the speaker, and not necessarily factual

read up on each and you can then apply to lightning, loops, rods, electrical, RF, marine protection, marine radio/radar and so on.

 

[dave*99]

three things to look for as regards this....

grounded
grounding
bonding

all have a very specific meaning and task to complete, but it seems like so many words today - meaning is in the mind of the speaker, and not necessarily factual

read up on each and you can then apply to lightning, loops, rods, electrical, RF, marine protection, marine radio/radar and so on.

Yes that’s correct.

 

[wyliesdiesels]

code requires all supplemental grounding electrodes (like those for phone and CATV) to be bonded to the primary electrodes that are part of the GES.

In your situation this creates an issue.

Cable co should be running the cable over to where the electrical service is located

 

[Terry D]

code requires all supplemental grounding electrodes (like those for phone and CATV) to be bonded to the primary electrodes that are part of the GES.

In your situation this creates an issue.

Cable co should be running the cable over to where the electrical service is located

I agree

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[sberry]

We usually have code quoters, what is it in? I guess I never did look at cable, just phone and maybe sat dish. It seems the best I can recall was if it was a certain distance you hook to electric and over could drive a rod.

 

[pattenp]

If the coax is bonded to the house grounding system you should not add another ground rod for the coax where it enters the house. This could cause lightning strikes to travel through the house. See mike holt video starting at 10:15....

 

[larry4406]

If the coax is bonded to the house grounding system you should not add another ground rod for the coax where it enters the house. This could cause lightning strikes to travel through the house. See mike holt video starting at 10:15....

Thanks pattenp!

In post 15 I discussed how I bonded Comcast's auxiliary electrode to the house grounding system (it had previously been standalone). I will disconnect it this weekend!