I recently bought a 250-foot Cat6 bulk box to make some custom-length Ethernet connections through my house, and I did what a lot of people do: go to Amazon, search for the product, buy it at a decent price and a ton of reviews. When I stripped a conductor and ran a knife blade across it, the copper fell away to reveal that the wire was actually copper-clad aluminum instead of solid copper, which wasn’t immediately alarming, because the wire and listing were marked as such with “CCA.”
After looking through the Cat6 specification, however, I found that any cable that uses aluminum as a conductor actually does not qualify as Cat6. Some of the best-selling cables and rolls of cables on Amazon are “Cat6” CCA, and while they are fine for the occasional patch cable, relying on these cables to carry a 5+ GbE or PoE connection can have not only performance consequences, but also security.
It’s a real Ethernet cable that can theoretically carry Cat6 speeds.
But it’s not real Cat6
Copper clad aluminum cables are exactly what they sound like: an aluminum conductor with a thin layer of copper deposited around the outside. The obvious reason for doing so is cost reduction, because aluminum is much cheaper than copper, but the physics argument also makes sense. High-frequency signals tend to travel along the outer surface of a conductor thanks to the skin effect, so the theory goes that data traveling over the copper skin doesn’t care much about what’s underneath. For the signal, this is somewhat true for shorter runs, but the problem comes with everything else.
I won’t bore you with the electrical details, but aluminum has about 61% more conductivity than copper, which translates to about 55% more DC resistance for the same gauge of wire. In layman’s terms, that higher resistance means more attenuation, and attenuation is exactly what reduces your margins on longer runs and at the higher frequencies that Cat6 is supposed to handle. Aluminum is also more brittle, so it is more likely to crack at a termination point and the aluminum oxide that forms when exposed to air does not conduct. That can easily result in a connection that feels good one day, but degrades as the weeks go by.
This is precisely why standardization bodies do not leave it open to interpretation. ANSI/TIA-568.2-D requires that category-rated cable conductors be solid or stranded copper, period. ISO/IEC 11801 says the same thing. A cable constructed with CCA conductors is not a Cat6 cable at alleven though the label is printed on the jacket and on the window advertisement. However, to be fair to this company, is marked CCA, so partial credit must be obtained.
PoE should stay away from aluminum
You need full copper
The skin effect that helps keep a CCA cable viable for carrying a Cat6 data signal does nothing for Power over Ethernet. PoE is DC and DC does not flow across the surface in the same way. You see the entire cross section of the conductor, which is primarily aluminum, and all that extra resistance shows up as two things: heat in the cable and voltage drop when power reaches your camera, access point, or doorbell. The practical result is often a device that shuts down or refuses to turn on, especially on longer rides, and gets worse as power budgets increase.
It gets worse: CCA cannot have a valid UL fire rating, which means placing it inside a wall, between floors, or across a plenum is not only inadvisable, it is outside the code in most jurisdictions that have adopted the National Electrical Code. That may void the listing your insurer assumes you have and may hold whoever installed it liable. Patch cords that run outside the walls could also be out of code, and in the event of an unrelated fire, finding a CCA cord could raise serious compliance questions, although that’s a bit of a gray area.
If you’re running 48V sustained PoE where corrosion is involved in the worst case, you could see that being a serious fire risk, but they’re certainly still a long way from the aluminum branch wiring house fires of the 1970s.
Some even go so far as to say that CCA wiring represents a serious fire hazard that can burn down your house, but the picture is a little more nuanced than that. There isn’t a wave of homes burning down because someone used cheap Ethernet, and the much more realistic failure you’ll see is an underpowered device or a connection that degrades over time. in addition to the fire rating that it no longer legally has. In my brief investigation I could not find any evidence of a fire caused by the CCA Ethernet cable, and using it only for data could almost certainly not cause a fire. If you’re running 48V sustained PoE where corrosion is involved in the worst case, you could see that being a serious fire risk, but they’re certainly still a long way from the aluminum branch wiring house fires of the 1970s.
How to know if your Ethernet cable is CCA
It will probably be printed somewhere.
Start with price: Pure copper is tough to cost, so if a coil is dramatically cheaper per foot than everything around it, that’s your first sign. Pick it up too. Aluminum is lighter and a CCA case feels noticeably less heavy than the same length of copper.
The jacket is the other clear clue. Honest sellers sometimes print “CCA” directly on the cable; many don’t print anything at all or bury it outside of the Amazon listing and only support it on the package. Real copper cable tends to loudly advertise the opposite: “bare copper” or “solid copper”, a UL certification and length markings.
If it’s a bulk roll, the easiest way to tell is to do what I did: remove a conductor and scrape its surface with a knife. If you scratch and see some silver, your cable is CCA. If it is a pure copper cable, it will be copper at all ends.
CCA is not a big conspiracy, but it is worth keeping an eye on
For strict data use cases where you don’t plan on pushing the limits of what the Cat6 spec is capable of, CCA cable is absolutely fine. But “Cat6” printed on a roll of copper-clad aluminum is a claim the cable simply can’t live up to, and it leaves a legitimate gap at the top end. Any type of long term, Using PoEor anything permanently locked in your walls It should be full copper wiring, and nothing less.
