Q&A: Ethernet Cable Jacket Types with Don and Dave

And we're back with another Q&A video! This time, networking experts Don and Dave take customer questions about Ethernet cable jacket types—the differences, when and where to use which ones, and much more.

Tune in below!

Don: Hey YouTubers, it's Don from trueCABLE coming at you again, and this time, I brought friends. We have the amazing Mikayla and the awesome Dave, and they're here with me to explain the differences between cable jacket types. Now, although we have extensive material in our Cable Academy that address cable jacket types, and what to use where, we still get questions. So, we have kind of maybe re-explained this in a different format, a Q&A session, that may help delineate the differences between what cabling gets used where, does color matter, stuff like that. Some of the more common questions we get that we didn't necessarily write down in the blog. So stay tuned. We're about to get right into it.

Mikayla: The first question we have today is for Dave, and it is: What is the difference between plenum and riser and which one gets used where?

Dave: Well, the difference in plenum cable and riser cable is in the chemical compounds that are used for the jackets and insulation in the interior of the cable.

Plenum cable is made for use in a plenum space. A plenum space is one that is also an air-handling space. That's what plenum means. And often, in a commercial situation, where you have a suspended ceiling, that area above the suspended ceiling is actually used as a cold air return for a heating system, for example. And if you have cable in a plenum area, in an air handling area, it has to have a certain fire rating, and plenum cable has a fire-rated PVC jacket. Whereas riser cable, which is also indoor cable, just has a PVC jacket that is not specially enhanced for fire resistance.

Also, the insulation used on the interior conductors is different. Plenum cable uses a fluorinated polymer for those conductors. And that means that they're going to be different chemical products due to combustion. And so, bottom line is: if it's a plenum space, you use plenum cable. If it's not, use riser cable, if you're indoors.

Most of the time, nowadays, the area above a suspended ceiling is not used as a plenum space. They have enclosed ductwork for the returns. And in that case, you don't have to use plenum cable. However, best practice is: you keep in mind that a non-plenum space above a suspended ceiling can easily become a plenum space by someone coming in and doing unauthorized work or incorrect work or corrosion or an earthquake. Who knows. Something could happen over the decades that this building is in service that would corrupt that ductwork system and turn a non-plenum space into a plenum space. So what I'm getting to is: anytime you're above a suspended ceiling, use plenum cable.

Mikayla: Thanks, Dave. Don, the next question is for you: can you use indoor cable outside if you use conduit?

Don: The short answer is: no, you should not do that. The reason is that outdoor cable in general is produced, or should be produced, using linear low density polyethylene, or LLDPE. And that's a significantly different kind of cable jacket material than standard PVC is. The problem with using indoor cable like riser outside, even in a conduit, is that the cable jacket on riser is permeable to water vapor. So what can happen is water vapor will get into the cable jacket, and this is a natural normal occurrence, but outdoors, water vapor that gets into the cable may coalesce and condense into liquid water inside the cable jacket once a temperature swing should occur. In other words, from warm to cold. And water vapor coming in and out of a riser-rated cable jacket is normal and it's a phenomenon that goes unnoticed, but if you have a wild temperature swing like you may experience, for example, in a outdoor scenario that can actually cause liquid water to form inside your cable, so, no, a conduit isn't enough. You would want to use the outdoor grade jacketed cabling and that is completely impervious to not only liquid water but water vapor as well.

Mikayla: Dave, we're gonna go back to you. So what is the right cable jacket to be used for direct burial? And does that change if the cables are also outside, but above ground, too?

Dave: Well, the material for outdoor cable jackets is LLDPE and that's the same for both direct burial and above ground. The difference in direct burial cable and above ground outdoor cable is inside the cable. Either water blocking tape under the jacket, or it's gel filled to exclude water from the interior of the cable.

Regular outdoor cable that's not rated for direct variable does not have that gel filling or the water blocking tape, but it's still water resistant because of that LLDPE jacket.

Oh, and I'm sorry. It's also UV resistant because of the LLDPE jacket.

Don: So the implication there is that the direct burial cable can be used above ground or below and the above ground outdoor jacketed cable is meant strictly to be used above ground because it doesn't have the additional protection.

Dave: That's correct.

Mikayla: Don, next question is for you. So why is Cat6A Riser ribbed on the inside?

Don: Typically, Cat6A unshielded cable is ribbed around the inside of the cable jacket. A lot of people may have wondered what that saw tooth thing looks like and also what it's for. So what we're looking at here is a cross section of Cat6A unshielded riser cable. And you can see that the inside of the cable jacket looks like it's got saw teeth, kind of like a reverse saw blade. Okay, so, the reason for that is… when cables are put into a bundle, what occurs is that additional space that the cable jacket provides with that saw teeth, that's basically a spacer. So that helps keep the conductors more separated, even when cables are bundled into a bundle and that helps prevent what's known as alien crosstalk. And when you start operating your cabling above 350 megahertz to achieve, for example, 10 Gigabit, then alien crosstalk starts to become an issue with the cable. So you start seeing that ribbing or shielding, another way of defeating that, but in the case of unshielded riser or Cat6A riser, you have the ribbing, and that's basically standoff ribbing, and it's to give the conductors more space between each other, even if the cables are in a bundle that's been velcroed together. So essentially, that's what it's for: to prevent one cable from interfering with another.

Mikayla: Don, another question for you. Is plenum Ethernet better than LSZH for plenum rated spaces. And can I use LSZH cable inside a plenum space in the U.S.?

Don: On Amazon and other international marketplaces, where you can pick up things made in other countries, you may notice various types of cable jacket ratings that you might not have heard of before. LSZH is a cable jacket type developed in the 80s in Asia and Britain. It’s know as low smoke zero halogen and that’s what that particular kind of cable jacket type is meant to do if it burns: emit low smoke and no halogen at all. The reason you started seeing LSZH developed in the 80s, and a plenum specification in the U.S. being developed in the mid 80s, is because of accidents that involve death or injury due to burning cables, in commercial building especially. In the U.S., we see LSZH and LSZH2 cable ratings, and neither of them meets the necessary criteria to achieve plenum rating in the United States. Now, there are cables out there that are LSZH and plenum rated. It'll be marked CMP or plenum and then slash LSZH, and those may be used in plenum spaces in commercial buildings, but if the cable is strictly just LSZH or LSZH2, that's not enough. Although they're less offensive cables if they burn, it doesn't fully meet the requirements necessary for the National Electric Code National Fire Protection Act. So, you may not use anything other than plenum rated cable in plenum rated spaces in the United States.

And if you go to our Cable Academy, we have a blog (CMP vs LSZH: Fire Rated Ethernet Cabling Explained) that really explains the difference between plenum and riser spaces and then it's going to show you some flame spread tests and carbon monoxide toxicity tests. They really demonstrate why plenum rated cable is what you want. So, I suggest everybody go to Cable Academy and give that particular blog a read. It goes in-depth about it.

Mikayla: This is gonna be our last question for today's Q&A. And Dave, I'm gonna give it to you. So does cable jacket color have anything to do with performance or cable selection?

Dave: It has nothing to do with performance and a lot to do with cable selection. The only difference between different colored cables, as long as everything else is the same (same category, jacket composition, etc.), the only difference is the dye used in the jacket. White cable will perform the same as blue cable or red cable. So why do we have all these different colors? Well, originally, there was a standard for which color to use. For example, horizontal cabling is specified to be blue. Backbone cabling is specified to be white. We have a table we can show you that shows that entire standard, but it's kind of an old standard now. Time has moved on. For example, backbone connections are usually fiber optics now. And so, more and more, colors are specified according to what the IT department wants them to be. For example, they may want all of their WiFi access points to be wired with purple cable so they can tell them apart from their POE lighting, which they do in orange cable, and that's just one example, but no difference in performance. You can really get by with selecting any color you want for any particular job you want.

Don: Okay, well, there you go. Hopefully, we've answered any last remaining questions about Ethernet cable jacket types. However, of course, if you haven't visited our Cable Academy at truecable.com, please do. We have an extensive number of blogs around selecting the right kind of cable jacket and the right kind of cable for your application. But each installation is different, and there's lots of different kinds of variations out there, so if you're ever in question, please absolutely give us a call. So with that said, you guys have a wonderful day. Happy networking.

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