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Wire Gauge - Another Hidden Detail

Back in the early 80's before adoption of any Category-X standards for wiring, we were faced with a decision that couldn't wait. At the time, we spoke with and visited AT&T (Atlanta Works Wire Division) Dupont, Belden, and Mowhawk Cable companies. The decision to begin the cabling project was pending as was the effort to begin selection of a product for the cable plant. We were about to wire a national landmark and everyone agreed it needed to last.

Back in the early 80's before adoption of any Category-X standards for wiring, we were faced with a decision that couldn't wait. At the time, we spoke with and visited AT&T (Atlanta Works Wire Division) Dupont, Belden, and Mowhawk Cable companies. The decision to begin the cabling project was pending as was the effort to begin selection of a product for the cable plant. We were about to wire a national landmark and everyone agreed it needed to last.Dupont made it very clear that using Teflon on cable for all cabling would prove beneficial since Teflon and other newer chemicals change and improve the dielectric properties of cabling. But the other problem besides performance was distance and what could we do to deal with the long cable runs of this project?

The folks at Belden had already tested their 24 AWG (American Wire Gauge) cable with the Teflon jacket to around 16 Mbps. At the time, they were also testing the idea of using 22 AWG to achieve much greater bandwidth. So as they say, it got down to the wire and we (two Chief Network Engineers - one data guy and one voice guy) decided to utilize Belden's wire and recommendation to go with 4-pair, Teflon coated, 22AWG cabling. What I can't remember is the tolerance window but what I do remember is that Belden's was very tight (more copper) compared to other brands we looked at and they were competitive for the nearly 1 million feet of Siamese cabling that we ended up purchasing for the first project.

For the SMB/E, these concerns (distance) don't come up as often. For L-enterprise, it better come up and someone needs to be paying attention. First, whether or not you migrate to IP or not- using Hybrid, pure IP, or anything- you need to consider other applications. For one example, anyone deploying DECT will find that you have distance limitations for the maximum cable length that you can place the Cell Stations or Access Points. These distances will vary by manufacturer. So if you are using direct buried cable between two or more buildings, chances are it is 26 AWG. One manufacturer providing DECT limits the access points to 750 feet using 24 AWG. But this is only one example and there are plenty of manufacturers for DECT, telephony, paging and other gear associated with communications. Remember, each manufacturer will specify their gear's distance limitation by wire gauge.

Another example is power over Ethernet (PoE). What is the minimum WATTS you need to light that IP phone up? Determine your cable plant wire gauge- look at the outer jacket(s) of the drops to determine this and don't forget to look at any riser or house cables too. Hopefully, whoever did the cabling was consistent and used the same wire gauge as we did on this old project. Otherwise, you are playing the odds. So in your cable plant assessments or quests to add new cabling, get the wire gauge right and consistently use the same wire gauge for ALL cabling and be sure to use a Teflon coating. Of course there will always be exceptions and I for one am betting that using Category 6, 6a or 7 if you can afford it for any wireless, will have greater chances to survive longer since it (wireless) is advancing. For interconnectivity of other voice, paging and PoE gear, consistency is a good thing to have on your side. A reality check will reveal that you do have Cat 5, 5E, 6, and maybe 6A and 7 embedded in your structured wiring. More than likely you are dealing, hopefully with IDF locations and managing upgrades when construction dictates and again, if you can afford it. In the SMB/E space- you get what you see and that's pretty much an evolution of everything, especially if the customer has been in the same place for any length of time.

Now- I am including the above statement- because, I haven't heard- is L-enterprise abandoning the use of structured wiring? Obviously you won't be using riser and house cabling for LAN interconnectivity (between IDFs) but you can still deploy IP phones over the existing infrastructure if you are considering a Phybridge migration or plan to adopt a hybrid solution. Either way, the type of cabling material used affects resistance and the deliverable power (WATTS) for any PoE required. Whenever there's a marginal PoE device, just look at both ends of the connection- look at what the switch is trying to deliver then go to the user faceplate and measure the delivered power- this is where you will see success or failure.

So size matters in a big way when you have distances to cover and you must include the total cable feet. Then, remember- Teflon isn't just for meeting fire code (National Electric Code)- that is a myth. Vendors will substitute PVC because of the huge difference in material cost. What you do get is a difference in performance, suitability for the application (UV or heat exposure, throughput) and the ability to cover greater distances for all your communications and power needs. I'm happy to say that at last look; if you ever venture to Washington Union Station and emerge from the escalators or descend to Metro using them, look straight up and you will see a dome ceiling, then above that dome is the MDF (Main Distribution Frame) still resting in place and home for all that wire.

I'll leave you with one last sporting TIP- "I hope the person maintaining what we put in, is still using 22 AWG cross-connect wire!" Size matters. For those of you that didn't know- Category 6A (The Big Daddy Cable) is now the TIA commercial building standard.