Q&A: Do You Really Need to Bond Copper Communications Cable to Ground?
Another Q&A session?! I think so! This time around, Don and Dave answer questions about bonding copper communications cable to ground. Want to learn more? Well...keep reading or listen to our podcast!
Don: Hey, everybody. Welcome back to the Low Voltage Lowdown. Thank you for joining us again to talk about bonding and grounding and do you really have to do it? We have Mikayla that'll be asking some questions. And we have Dave and myself. I'm Don Schultz, and we're going to get into the questions.
What is bonding and grounding and is this also earthing?
Don: All right. So we're going to take the second question first, which is going to be the easier one to answer. Earthing is the same thing as grounding. They are one in the same. You'll see it referred to differently depending on what source you read.
So, the bonding is more of a process than a thing. The way you should term it is bond to ground. So bonding something is establishing a low resistance electrical path for EMI/RFI and electrostatic discharge (ESD) to drain off to ground. When we say ground, we're talking about the AC system ground, which is earth ground.
It's very confusing and bonding and grounding are interrelated. You can't have one without the other. But at the same time they are separate terms and they do mean separate things. A ground is more of a something that happens and bonding is something that you do to get to ground.
When does copper communications cable need to be bonded to ground?
Dave: Well, when it shielded cable it needs to be bonded to ground. At least that shield needs to be bonded to ground for it to function properly. There's a foil shield or perhaps a braided shield underneath the jacket.
This is often accompanied by what's called a drain wire. If present, it needs to be bonded to ground. This is usually done through termination hardware. Also, if your communications cable is armored and that armor is conductive, like made out of aluminum or steel, that armor has to be bonded to ground.
Does unshielded copper communications cable get bonded to ground?
Don: Oh, good question. The answer is no. You only bond a cable to ground if it's got an armored sheathing, as Dave said, or a cable shield. So unshielded cable does not get bonded to the ground. But that question does come up a lot and people call in about how to bond unshielded cable, and that's something you don't need to do. That's only something that applies if the cable has a braided or a metallic foil shield or armoring on it.
Is using a lightning protector bonding to ground? Is that the same thing as bonding the cable shield?
Dave: Using a lightning protector does require bonding to ground, but it does not bond the communications cable to ground.
If the communications cable going through a lightning surge protector is shielded, that shield is carried through just as the communications pathways are. And also in the case of an overvoltage condition, like if there is an actual surge and that lightning protector clamps to ground, then the shield is open as well as all the communications pathways. So bonding to ground is necessary, but it's the protector that you're bonding, not the cable itself.
What is part of the cable shield and how does it bond to a shielded patch panel?
Don: Good question, Mikayla. So the inside of the Ethernet cable, if it's a shielded cable, you're going to have an electrostatic drain wire. It's basically copper with a tin coating on it. And it'll be used in conjunction with the foil shield that's also found inside the cable or could be a braid shield. You could have a combination of these items.
When you terminate your hardware, keystone jacks or shielded RJ45 plugs, to the Ethernet cable, the cable shield and drain wire or some combination thereof will make a bond with the actual termination hardware. So that's why shielded hardware is metal, for example. So when you bond the cable shield to the hardware, then the hardware literally functions as an extension of the cable shield.
When you then take that metal keystone jack and you snap it into a shielded patch panel, like a tool-less shielded a patch panel, for example, then the patch panel effectively becomes an extension of the cable shield. Every time you're terminating your shielded hardware properly to your shielded Ethernet cable, you're bonding the cable shield to that. It then bonds to the shielded patch panel. You can have an additional bond with a shielded patch cord as well.
If I'm using coaxial cable, does it always have to be bonded to ground?
Dave: Well, the short answer is yes, but that's probably not very helpful because if you're working on the coaxial cable in your home or place of business, you're probably not the person who's going to have to worry about bonding it to ground unless you're the person who's installing the service to the building.
And that's because where that service enters the building, where the coax cable enters the building from the provider, there is a little coupler there. And that coupler is connected to both of those f connectors. The one coming in from the pole probably, and the one going into the house. Those come together in a coupler and that coupler has a lug that is bonded to ground.
Then, because of the way the cable is constructed with the braided shield on the outside, that is also a conductor. That braided shield is also connected to the f connector. So by virtue of the fact that that coupler is bonded to ground, all of the coax in the installation should be bonded to ground there.
Don: So effectively it's just like the shielded keystone jack like with the Ethernet cable that's hooked up with shielded Ethernet cable.
In the case of coaxial cable, though, because you've always got a shield, your F connector becomes an extension of the cable shield, and it also becomes a second part of the conductor circuit, because coaxial cable has a conductor circuit that is two part.
What can happen if you do not bond your communications cable to ground?
Don: The first thing is that the cable shield is not going to function properly. Now, what are the negative effects you could experience? Probably nothing. Most of the time you're not going to have a severe enough issue in the environment that required you to actually install shielded cable anyway. But if you actually do have a problem in your environment where there's often like an electrostatic discharges or EMI/RFI, if you don't bond your communications cable to ground, that could cause intermittent issues with your data transmission.
It could result in your cable literally functioning as an antenna. And if you don't bond your communications cable to ground, then you're subject to possible Murphy's Law. So, I mean, assuming you put in your shielded communications cable, obviously in order to bond to ground it has to be shielded, if you put that in, then you are looking to avoid a problem.
So if whatever problem you're looking to avoid, if it's not properly bonded, it's not going to help you avoid the problem, you wasted money. But most of the time, if you don't do it right, your cable is still going to work. It's not going to actually cause any real problems. But there are circumstances where it absolutely will cause a problem. It's all installation dependent.
Hopefully this helps clear up some of the common misconceptions around bonding and grounding and what earthing is and what can happen when you don't bond your cable shield properly. This is a pretty complicated topic. We have two very large blogs with videos present in our cable academy, one that addresses residential installations and one that also addresses commercial installations. Check out Residential Bonding and Grounding of Shielded Ethernet Cable Systems and Commercial Bonding and Grounding of Ethernet Cable Systems to learn more!
With that, I'm going to say you have a great day and happy bonding!
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