Residential Bonding and Grounding of Shielded Ethernet Cable Systems
Written by Don Schultz, trueCABLE Technical Manager, BICSI INST1, INSTC, INSTF, Fluke Networks CCTT
It is rare to actually need shielded Ethernet cable in a residential setting. Many DIY installers (homeowers) have a perception that shielded Ethernet is “better”. After all, wouldn’t shielded be somehow better than unshielded Ethernet? Well, oftentimes the answer is “no”. Shielded Ethernet does not make your cable any faster. The shielding is designed to mitigate EMI/RFI interference or potential ESD discharges that you know you need to avoid. That said, there are legitimate circumstances for the use of shielded Ethernet cable in a residential environment and they are covered in Ethernet Cable Shielding Types as well as Top 2 Things to Consider When Running Ethernet and Power Cable.
The two most common scenarios where shielded Ethernet cable is recommended in a residential installation are:
- You are unable to maintain a 8 inch separation distance from “Romex” unshielded AC circuits or electrical panels (common 120/240V)
- Outdoor runs that result in the cable being suspended above the ground, in the air, between two structures. This could be two buildings or a single building to a flagpole, for example.
So, you might need bulk unterminated shielded Ethernet cable. Just be aware of what you are signing up for. Shielded Ethernet comes with some “penalties”:
- Higher costs for the cable and hardware
- More complex termination technique
- Shielded cable is more difficult to install due to tighter restrictions on bend radius, weight, and reduced flexibility
- Shielded Ethernet must be bonded to ground
Of the four disadvantages pointed out above, the fourth one about bonding to ground is probably going to cause you some anxiety. Most residential installers are at a total loss as to how to bond shielded Ethernet cable to ground. Even worse, you may have some incorrect preconceived notions about what to do. That is the focus of this blog: How to bond your Ethernet cable so that the EMI/RFI or ESD encountered is channeled safely to your AC ground system.
Getting a Bit Technical for a Moment
This blog will make more sense if we cover some basic terms. There is a large amount of misinformation and confusion about bonding and grounding of anything, not just Ethernet cable shields. Let’s take some information from another blog I wrote about Commercial Bonding and Grounding of Ethernet Cable Systems. The same concepts apply, but on a smaller scale. I recommend you read the commercial blog if you have a moment.
Are Bonding and Grounding the Same Thing?
Nope. They are highly related, though. In fact, one is sort of useless without the other. That is why you see the terms right beside each other when discussing this topic.
People get the terms “bonding” and “grounding” all confused and mixed up. We need to separate the two highly related, but essentially different, terms.
But, here is a hint:
Bonding is more of a process and result, where grounding/earthing is more of a result only. If you are an installer, then you are bonding to ground. If that does not make sense, then I don’t blame you!
What is Bonding?
Generally, the term bonding is the process of establishing a low resistance electrical path from one conductive object to another so that unwanted voltage has a path to ground in adverse events such as:
- EMI/RFI (Electromagnetic and Radio Frequency Interference)
- Electrostatic discharge (ESD)
- Electrical system faults
What is Grounding?
Grounding is also referred to as “earthing”. They mean the same thing. Conceptually, grounding is to establish a zero (0) volt reference potential to earth. The ground is between the earth itself and the electrical system inside your house. Its purpose is to provide an intentional path for fault current, and provide a path for ESD to drain off to. The idea is to equalize the earth’s potential with the electrical system potential, and all equipment or enclosures that are part of that system. Ground rods (called ground electrodes) and GECs (Ground Electrode Conductors) are used for this purpose.
For residential installations you likely won’t have to worry about bonding ladder racks, cable tray, metallic conduit, and equipment racks. So, the main thing you will have to worry about is bonding your Ethernet cable shields to ground and using some sound techniques.
It All Starts With the Cable Shield
trueCABLE sells a variation of shielded cable called F/UTP. That means the cable has an overall foil shield and the individual pairs are not shielded. In addition to that foil shield there is a drain wire (tinned copper wire) that makes contact with the cable shield. The drain wire helps you bond your cable shield to the connection hardware.
Shielded Ethernet cable. Cable shield folded backwards and the drain wire wrapped around the shield.
Close up view. Cable shield has been trimmed to leave what is needed for a good bond. Note drain wire wrapped around the shield and jacket.
Rear of shielded tool-less keystone jack showing bond leaf spring. The cable shield and/or drain wire should make contact with this to establish a good electrical bond with the cable shield.
Once the keystone is closed, the cable shield is now bonded. Best practice is to bond BOTH ends of the cable shield.
Did you know that once your cable shield is electrically bonded to the keystone jack the outside metal of the keystone jack becomes part of the cable shield and drain path? Now they function as a unit. Pretty cool, huh?
Other connection hardware bonding methods:
- Removal of cable shield and use of wrapped drain wire only
- Removal of cable shield and use of copper conductive adhesive tape to tack down the wrapped drain wire. This is most useful for shielded RJ45 8P8C terminations. Learn more in How To: Copper Fabric Strips for Bonding Shielded Ethernet Cable
Once your cable shield has been properly electrically bonded to your termination hardware (shielded keystone for example) you will need to continue that bond. How do you do that? Well, there are three ways depending on your equipment and environment:
- Tool-less shielded patch panel that is bonded to ground already
- Tool-less shielded patch panel that is bonded to ground already and you also use shielded patch cords to your properly grounded Ethernet switch (best way)
- Use of a shielded patch cord only to your properly grounded Ethernet switch
What is a properly grounded Ethernet switch? Basically any Ethernet switch which uses a three prong power cord. 19-inch rack mount switches with their own AC/DC internal power supplies fit the bill.
A small desktop Ethernet switch with an external two prong AC/DC adapter (wall wart) is NOT properly grounded! It cannot serve as the path to ground for your Ethernet cable shield. In this case, you MUST separately bond your shielded patch panel to ground with a “ground wire”. Which means, of course, you have to use a shielded patch panel. You may not have expected that.
Essentially, there must be a way for your Ethernet cable shield to drain off to your AC ground somehow. Here are some schematic examples:
Method #1 - GOOD - AC Powered Ethernet Switch (no AC/DC adapter)
- Method #1 does not make use of the auxiliary bond wire (green wire) that is typically included with shielded patch panels
- Method #1 absolutely requires an AC powered Ethernet switch, using a 3 prong power cord
- Method #1 absolutely requires all components like patch cords and keystone jacks to be shielded
- At the remote wall mounted keystone jack, a shielded patch cord should also be used to the destination powered device to increase the number of bond points to your AC system ground to two
Method #2 - BEST - AC Powered Ethernet Switch (no AC/DC adapter) with Auxiliary Bond Wire Backup
- Method #2 makes use of the auxiliary bond wire (green wire) that is typically included with shielded patch panels, but you may need to create your own**
- Method #2 absolutely requires an AC powered Ethernet switch, using a 3 prong power cord
- Method #2 absolutely requires all components like patch cords and keystone jacks to be shielded
- At the remote wall mounted keystone jack, a shielded patch cord should also be used to the destination powered device to increase the number of bond points to your AC system ground to three
Method #3 - DC Powered Ethernet Switch Using AC/DC Power Adapter
- Method #3 absolutely relies upon the auxiliary bond wire (green wire) that is typically included with shielded patch panels, but you may need to create your own**. The bond wire is attached to the AC outlet faceplate, below the center screw. See video!
- Method #3 addresses small 5 port to 16 port residential style Ethernet switches that usually do not have internal AC to DC conversion and instead rely upon external adapters
- Method #3 requires shielded keystone jacks, but the patch cord from the patch panel to the Ethernet switch does not need to be shielded
- At the remote wall mounted keystone jack, a shielded patch cord should be used to the destination powered device to increase the number of bond points to your AC system ground from one back to two, if possible
Help! It won’t Reach
Shielded patch panels come with a laughably short bond wire, typically 18 AWG and only about 12 to 16 inches. If the shielded patch panel is mounted in a rack with a rack busbar then this is not an issue, but residential installations don’t typically involve racks, much less fancy and expensive rack busbars.
**You will likely need to create your own bond wire. That is easy to do.
Pick up the following items from your local Home Depot or similar store:
- 10 or 12 AWG (don’t go smaller than 12 AWG) THHN green stranded copper wire
- Ring terminals to fit 10 or 12 AWG stranded THHN stranded copper wire
- Crimp tool to crimp down the ring terminals
- Electrical wire stripper tool
- Take note that when selecting the ring terminals, be sure to pick the ones that will accept your wire and also won’t be too big or too small for the screw on the patch panel or the screw on the AC outlet faceplate. You may need two sizes.
- Cut a length of the THHN stranded copper wire, not to exceed six feet
- Strip both ends of the stranded copper wire with proper wire strippers
- The insulation should go right up to the point where the copper enters the ring terminal, but not inside the ring terminal.
- The copper conductor itself should be long enough and be visible at the end of the “inspection window”
- Remove the existing bond wire from the patch panel
- Attach one end of your new bond wire to the patch panel and the other end to the center screw of an AC outlet. See video for how this looks.
Common Questions & Advice
Let’s address some common questions and give some tips that will help you.
Question: “I have been told that you should only ground the Ethernet cable at one end. Is this true?”
Answer: “Sometimes yes, but only if you are seeking to avoid a ground loop. You likely don’t have to worry about this. If you are running shielded Ethernet between two structures that have their own separate AC systems or separate grounding rods installed, then YES, you should worry about what is known as a ground loop. A ground loop occurs when you have actual conflicting AC ground systems. Merely bonding your Ethernet cable at multiple points to the same AC grounding system in a single structure does not create ground loops. Think in terms of ground rods. How many ground rods are involved? If you have more than one with more than one structure involved then you are wise to bond to ground at a single end only.” How To Fix a Ground Loop is a good resource to read more about this topic.
For single structure Ethernet installations, you want to bond your cable shields to your single AC ground at as many points as possible. The more bonds to ground the better the shield will function.
Question: “What happens if I don’t bond my Ethernet cable shields to ground? Will I damage anything?”
Answer: “This is known as a floating cable shield. That means the Ethernet cable shield is not able to drain off EMI/RFI/ESD to your ground system. You probably won’t have any problems at all, as most residential situations don’t have large sources of EMI/RFI to cause a big enough issue with a floating cable shield. By not bonding your shields to ground you just wasted money and your shielded cable is not actually shielded anymore. Now, there is the slight possibility you will encounter actual trouble by not bonding those cable shields to ground and this can show up as lower than expected speeds or even an ESD event that could damage equipment.”
If you are considering installation of shielded Ethernet cable and are unable or unwilling to bond the cable shields to ground then opt for unshielded Ethernet cable for your installation. You will save money and headaches.
Question: “Do I need to pound in a ground rod for all of this to work right?”
Answer: “No. Do not do that! Your home already comes with an AC grounding system you can bond to and your AC panel is already connected to a ground rod. If you pound in a separate ground rod you just created an alternate and potentially conflicting point of ground. You can actually create yourself a ground loop doing this. There are rare circumstances where you may need to pound in a ground rod and bond to that, but that is beyond the scope of this blog.
If your home passed inspection and was built in the last 40 years you should have three prong grounded AC outlets. Check to be sure your outlets are properly grounded by using a three prong outlet tester. If you get a test result that is anything other than “CORRECT” talk to an electrician!
So, there you have it. A subject that has been the source of many questions and anxiety for residential installers finally explained in one spot. With that, I will say…
trueCABLE presents the information on our website, including the “Cable Academy” blog and live chat support, as a service to our customers and other visitors to our website subject to our website terms and conditions. While the information on this website is about data networking and electrical issues, it is not professional advice and any reliance on such material is at your own risk.