Cat6 building entrance protector grounding

rbaevergreen

Member
Location
Upstate New York
Occupation
IT Systems Engineer
I ran Cat6 (shielded, flooded) between my house and detached garage. I'm terminating each side with ITW Linx CAT6A-75 primary protectors. Each building has ground rods within 20 ft. or less of the entrance protectors. Should I be using a spilt bolt to attach to the bare ground wire by the ground rod or can I use a zinc ground clamp and connect directly to the ground rod? I'm thinking that it does not matter but the cable company attached to the ground wire at the house side.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
The only thing that matters is whether those ground rods are properly bonded to:
A) The service at the house end.
B) The EGC in the sub panel at the detached garage end.

By themselves, ground rods are next to useless.

-Hal
 

rbaevergreen

Member
Location
Upstate New York
Occupation
IT Systems Engineer
OK that makes sense thanks. It sounds like I can just attach the ground off the CAT6A-75 to the bare ground wire in the house at the service end as well as the subpanel's ground wire at the detached garage end? Not inside the panel, but the same way the cable company just attached to the bare ground.

Second question, which I really hope doesn't make me regret not going fiber or wireless: the detached garage was built around 1987 and the subpanel has 100 amp 240v service from the house. While the subpanel has separate ground rods, there are only two hots and a neutral coming over from the house. The grounds and neutrals are bonded at the garage's subpanel. It looks like this was legal up until 2008. Since the Cat6 cable is shielded and the shield connects to these building entrance devices, which are grounded, do I accidentally create a secondary return path for the neutral this way over the Cat6, or am I overthinking this?
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Welcome to the forum.
Should I be using a spilt bolt to attach to the bare ground wire by the ground rod or can I use a zinc ground clamp and connect directly to the ground rod? I'm thinking that it does not matter but the cable company attached to the ground wire at the house side.
You're correct, and cable installers are lazy.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
While the subpanel has separate ground rods, there are only two hots and a neutral coming over from the house. The grounds and neutrals are bonded at the garage's subpanel. It looks like this was legal up until 2008. Since the Cat6 cable is shielded and the shield connects to these building entrance devices, which are grounded, do I accidentally create a secondary return path for the neutral this way over the Cat6, or am I overthinking this?
Yeah, you do. I don't think a 3-wire feeder was legal even back then if you had other metallic pathways from one building to another, like a water line or telephone line.

-Hal
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Since the Cat6 cable is shielded and the shield connects to these building entrance devices, which are grounded, do I accidentally create a secondary return path for the neutral this way over the Cat6, or am I overthinking this?
That is a concern, as the shield would be sharing neutral current. If you're sure that the shield connects to the ground wires, I would have to recommend leaving one end floating.
 

rbaevergreen

Member
Location
Upstate New York
Occupation
IT Systems Engineer
Yeah, you do. I don't think a 3-wire feeder was legal even back then if you had other metallic pathways from one building to another, like a water line or telephone line.

-Hal
Luckily there aren't any metallic paths yet (the previous owners did something with a cable wire but I don't believe this is connected now). Nothing would surprise me with any of this - the PVC conduit is also buried 3-12 inches depending on where. It won't be cheap to correct the 3-wire feeder to 4-wire feeder but it probably isn't a bad idea if the burial depth is that shallow to correct both at once.

That is a concern, as the shield would be sharing neutral current. If you're sure that the shield connects to the ground wires, I would have to recommend leaving one end floating.
Interesting - so just connect the entrance protector at the house end and then splice the outdoor to indoor cable with a block at the garage side (minus shield) until I upgrade to 4-wire feeder?
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
You are still going to have the pairs themselves. Even though with ethernet they should be isolated from ground I'm not sure I would be comfortable with working on my laptop and then touching some other grounded electrical device.

I wouldn't mess with this. Get an EC to upgrade it for you.

-Hal
 

rbaevergreen

Member
Location
Upstate New York
Occupation
IT Systems Engineer
Fiber is the proper solution.
Fiber is a good solution if I kept it at 3-wire feeder but it's only 100 feet. Another concern people had with copper over fiber was that the buildings would be at different ground potentials, but since they grounds will be connected I don't see how they would be at different potentials.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
Because the neutral in the existing 3 wire feeder is current carrying, any 120V load at the far end is going to result in a voltage drop along that wire that results in the garage being at a lower potential than actual ground. If the EGCs are connected to that neutral in the garage then anything connected to that "ground" is going to have a voltage difference compared to, say, your CAT6 shield that is tied to ground back at the house. While that voltage may not normally be significant, it will increase during the times when motors or A/Cs start, causing a heavy load. Also consider what the current from a fault or short circuit will do to that voltage difference. I have seen voltage differences of as much as 50 volts from a receptacle ground pin to building steel that destroyed my communications equipment because the equipment was grounded to the steel and connected with a grounded 3 wire line cord and plug.

So the Code was changed to require a separate ground conductor in the feeder to reference everything back to the one service ground in the main panel. No more problems.

-Hal
 

rbaevergreen

Member
Location
Upstate New York
Occupation
IT Systems Engineer
The fiber idea sounds really good right about now. But out of curiosity, does the separate ground conductor tend to keep both buildings at the same ground level or might you get issues like the 50v issues you saw earlier?
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
As Larry stated you do not want to bond both ends of the CAT6 with a 3 wire feeder to the garage and a bonded neutral. Is bonding the CAT6 at the garage really necessary?
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
The fiber idea sounds really good right about now. But out of curiosity, does the separate ground conductor tend to keep both buildings at the same ground level or might you get issues like the 50v issues you saw earlier?
With separate grounding (EGC) and grounded (neutral) conductors, the potential at both ends of the EGC will remain at zero volts, even if there is a voltage drop on the neutral, which manifests as a voltage between neutral and ground.

You would NOT want to parallel the CAT-6 shield with the neutral, whereas it would be okay to parallel it with the EGC. Approximately half of the neutral current would try to flow on the cable's shield if you do it with a 3-wire feeder.
 
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