Comcast Bonding & Grounding

[warrant2002]

Recently California Comcast issued an addendum to their official Grounding & Bonding requirements as per the SCTE and the NEC. I am in agreeance with these new practices if, and only if, done correctly with the exception to three things.

That is the following; The new ruling states that there are roughly 3 correct ways to bond the cable system. 1.) An Earth grounded water pipe system, 2.) A Eufer grounding system, 3.) The Electrical breaker panel.

One of the old forms of grounding has been denied for use and that is any type of grounding rod, no matter its length or diameter.

Now, I have three concerns regarding these new rulings.
1.) Some houses, especially those built prior to 1970 do not have a formal grounding system and are usually on a 2-prong outlet setup and the electrical breaker boxes aren't even grounded themselves, Comcast does not expect all of it's employees to be EC and therefore not know the difference between the two.

2.) A retrograded grounded power box will itself contain a grounding rod using 1/2" rebar at least 6' deep and so why is it that we can use this type of ground through the meter panel but not solely by itself.

and last but not least,
3.) A properly installed rebar grounding rod has been proven to be the most effective type of grounding system but yet this is the least favorable with the NEC and therefore, Comcast. Even a far superior choice over the structures water pipe system which can fail when there is an unobservable break in the metal piping due to plumbing repairs using plastic components or possibly even plastic mains coming from the city's water plant?


Please if anyone has more information specifically regarding Comcast's grounding procedures please email me at XXXXXXXXXXX. Thank you


Moderator Note, send a PM to contact warrent

 

[iwire]

1.) Some houses, especially those built prior to 1970 do not have a formal grounding system and are usually on a 2-prong outlet setup and the electrical breaker boxes aren't even grounded themselves, Comcast does not expect all of it's employees to be EC and therefore not know the difference between the two.

There are no electrical services that are not in fact grounded, even if there are no grounding electrodes on the premises the service panel is still grounded via the grounded conductor from the utility.

3.) A properly installed rebar grounding rod has been proven to be the most effective type of grounding system but yet this is the least favorable with the NEC and therefore, Comcast. Even a far superior choice over the structures water pipe system which can fail when there is an unobservable break in the metal piping due to plumbing repairs using plastic components or possibly even plastic mains coming from the city's water plant?

I have no idea where you heard a ground rod is the most effective grounding electrode.....it is not.

Lastly it is much less important that you have a great connection to earth compared to the need to have the cable shield and the premises grounded conductor firmly bonded together and at the same potential.

 

[iwire]

Here are the places the NEC allows grounding cable.

(1)The building or structure grounding electrode system as covered in 250.50

(2)The grounded interior metal water piping system, within 1.52 m (5 ft) from its point of entrance to the building, as covered in 250.52

(3)The power service accessible means external to enclosures as covered in 250.94

(4)The metallic power service raceway

(5)The service equipment enclosure

(6)The grounding electrode conductor or the grounding electrode conductor metal enclosure

(7)The grounding conductor or the grounding electrode of a building or structure disconnecting means that is grounded to an electrode as covered in 250.32.

 

[brian john]

The reason (I would think) why they avoid the driven rod, is the propensity to attach the cable ground only to this rod that is not connected (and most likely won't be) to the premises ground electrode. As noted above the grounding system utilize on site is the ground you should be using.

 

[iwire]

There are no electrical services that are not in fact grounded, even if there are no grounding electrodes on the premises the service panel is still grounded via the grounded conductor from the utility.

I have to clarify, that should say

There are no dwelling unit electrical services that are not in fact grounded.....

 

[Pierre C Belarge]

One of the reasons they may not want driven ground rods for Comcast is, they do not want their techs driving ground rods through the water or gas services.




And I agree with Bob about this...
3.) A properly installed rebar grounding rod has been proven to be the most effective type of grounding system but yet this is the least favorable with the NEC and therefore, Comcast. Even a far superior choice over the structures water pipe system which can fail when there is an unobservable break in the metal piping due to plumbing repairs using plastic components or possibly even plastic mains coming from the city's water plant?


I am interested to see where he has received this kind of information.

 

[brian john]

Pierre:

Even if it i a poorly grounding service (one rod more than 25 ohms [just for grins]), I believe they are better off with the cable connected to this ground, than a separate low resistance ground electrode. (As Bob alluded too)

 

[nakulak]

I agree with the whole idea that cable, phone, tv, etc. installers be required to bond to the elect service. Since they are not expected to be adept at proper NEC grounding practices, why should they be put in the position to fail ? This makes great sense. Imaging if the phone/cable installer poorly grounded their system to their own ground. Imagine that the cable accidently became energized due to an electrical fault. With the poorly grounded/non-bonded system, a phone user who happened to be in contact with, say, a metal appliance would then be the path to ground (electrocution). On the othe hand, if the system were bonded per the directive above, it would fault the energized ckt directly.

 

[mdshunk]

In my area, Comcast uses one of two types of fittings purpose-built for latching onto the metal of the meter can. One is a little triangle that hooks on the corner, and one is an adjustable "bar clamp" that spans from side to side on the meter can. Both of these clamps have a terminal to connect the cable bond wire. I'm not really sure why the Comcast folks in Cali aren't aware of both of these simple fittings.

 

[Pierre C Belarge]

Pierre:

Even if it i a poorly grounding service (one rod more than 25 ohms [just for grins]), I believe they are better off with the cable connected to this ground, than a separate low resistance ground electrode. (As Bob alluded too)

Would you mind expounding on this comment?

 

[Pierre C Belarge]

In my area, Comcast uses one of two types of fittings purpose-built for latching onto the metal of the meter can. One is a little triangle that hooks on the corner, and one is an adjustable "bar clamp" that spans from side to side on the meter can. Both of these clamps have a terminal to connect the cable bond wire. I'm not really sure why the Comcast folks in Cali aren't aware of both of these simple fittings.

230.66
The last sentence explains that single meterpans are not considered as service equipment.
The NEC requires that the grounding conductors be terminated to service equipment. 250.94

Technically the meterpan termination by "other systems" may be a violation...even though it is an industry standard.

I am curious what others have to say about this.

 

[mdshunk]

230.66
The last sentence explains that single meterpans are not considered as service equipment.
The NEC requires that the grounding conductors be terminated to service equipment. 250.94

Technically the meterpan termination by "other systems" may be a violation...even though it is an industry standard.

Is Comcast even bound by the NEC? They're a public utility, so it would seem. Not saying, just asking.

Here's the fittings I was talking about:

http://www.tnb.com/pubint/docs/diamond_sachs_us.pdf

 

[iwire]

Technically the meterpan termination by "other systems" may be a violation.

820.100(B)(1)(4) allows bonding to the metal service raceway.

I guess an AHJ could consider the meter pan part of the service raceway.

 

[Pierre C Belarge]

Marc
Somehow I knew you would be the first to respond. :grin:


I believe in this instance, that they not only follow the NEC, but also the NESC. I believe for this type of installation the two documents have similar requirements.
Just to expand a little. The NEC requires US (notice the emphasis I give US - meaning "inside wireman") to provide a means for the "other systems" type of installation.

P.S. I wonder how the cable or phone company installer is even sure if the meterpan is grounded?

 

[iwire]

Is Comcast even bound by the NEC? They're a public utility, so it would seem. Not saying, just asking.

It's a yes and no, check out 90.2(B)(4).

It seems this grounding done outside the building is outside the NEC jurisdiction, once inside a customers building the NEC does apply to them

 

[mdshunk]

820.100(B)(1)(4) allows bonding to the metal service raceway.

I guess an AHJ could consider the meter pan part of the service raceway.

If not, there's a fitting for the raceway too:

 

[mdshunk]

P.S. I wonder how the cable or phone company installer is even sure if the meterpan is grounded?

Umm... not sure I follow. If the building is served with electricity, it is a physical impossibility to not have a grounded meterpan due to the way they are constructed. If the building lacks a main bonding jumper and a grounding electrode system, the utility's multigrounded neutral is grounding the meter can.

 

[mdshunk]

I believe in this instance, that they not only follow the NEC, but also the NESC.

So they pull permits and you inspect their work? :roll: Their men licensed electricians?

 

[Pierre C Belarge]

Umm... not sure I follow. If the building is served with electricity, it is a physical impossibility to not have a grounded meterpan due to the way they are constructed. If the building lacks a main bonding jumper and a grounding electrode system, the utility's multigrounded neutral is grounding the meter can.

Marc
It is possible that a meterpan with an isolated neutral is installed by accident..I have come across it during inspections - stock item installed by one not taking a close look at what he grabbed off the storeroom shelf.

Also, the straps you show... I am not too sure, but I remember in a UL meeting the UL rep saying those type straps with holes in them (as yours show) are for indoor type installation only. There is a strap available without the holes - of course they are more costly.
I know you are good at finding this stuff...maybe you could locate it.

 

[mdshunk]

Also, the straps you show... I am not too sure, but I remember in a UL meeting the UL rep saying those type straps with holes in them (as yours show) are for indoor type installation only. There is a strap available without the holes - of course they are more costly.
I know you are good at finding this stuff...maybe you could locate it.

The pure copper one's aren't for outdoors, but the galvanized one's are. Says so right in the catalog. The one I liked to was galvanized.