CAT 6 cable in the same conduit as THWN wiring?

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tthh

Member
Location
Denver
Occupation
Retired Engineer
I once got a tour of a fiber optic cable manufacturing plant. One of the tests this plant performed on the final spool was to run a video signal though the fiber spool and show a test pattern on a TV. They found that using a modern TV with a digital TV signal never showed marginal fiber, while an older analog TV and signal showed marginal fiber as distortion in the test pattern.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I once got a tour of a fiber optic cable manufacturing plant. One of the tests this plant performed on the final spool was to run a video signal though the fiber spool and show a test pattern on a TV. They found that using a modern TV with a digital TV signal never showed marginal fiber, while an older analog TV and signal showed marginal fiber as distortion in the test pattern.
That should surprise no one. Digital signals are generally error checked while analog signals can just go all over the place.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
That should surprise no one. Digital signals are generally error checked while analog signals can just go all over the place.
In the olden days when you were watching TV over the air and the signal was weak, the video would get "snowy" but you could still watch it until it got really bad, and the audio was the last thing to crap out. These days if the signal degrades you get video shredding and freezes along with "goat boy" audio. It either works perfectly or it doesn't work at all. Is that better? :D
 

Jon456

Senior Member
Location
Colorado
In the olden days when you were watching TV over the air and the signal was weak, the video would get "snowy" but you could still watch it until it got really bad, and the audio was the last thing to crap out. These days if the signal degrades you get video shredding and freezes along with "goat boy" audio. It either works perfectly or it doesn't work at all. Is that better? :D
Reminds me of the days of adjusting the rabbit ear antenna on the TV "just so" to get the best signal. Sometimes, you had to not let go of it because your body contact improved the reception! 🤪
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
Your only options are in 725.136(I).
Allen Bradly makes a 600 Volt rated Cat5 cable I have seen used. Its cat5 not 6
The 600V sheath is as thick as any barrier, so an AHJ might agree it meets the requirement of a barrier 725.136(B). There is no NEC definition of a barrier in that context.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
How would one know this? Are network devices (routers, switches) so marked?
It really gets down to the definition of a communications circuit. The rules in 800 (805 in the 2020) for communications equipment end at the load side of the first customer owned equipment. This also puts phone wiring on the building side of a private PBX into Article 725.
"Article 725 Class 1, Class 2, and Class 3 Remote-Control, Signaling, and Power-Limited Circuits."
The ethernet circuits and phone circuits on the building side of the equipment are considered "signaling" circuits and are covered by 725.
There is no practical difference as the rules in both 725 and 805 are almost identical.

Note that there are really no specific rules for "signaling circuits" in Article 725, but the Class 2 rules are typically applied to those circuits.
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
How would one know this? Are network devices (routers, switches) so marked?
Just take a peek in your network closet, look at the power supply for your network switch or router, dont accidentally unplug your office network, do you see anything that says class 2 on it?
That would be a art 725.121 (A)(2) class 2 power supply.
A communications circuit as defined by article 800, I think of like 'service conductors' they originate from a provider, enter the building then go to all the customer owned equipment such as old landline phone, fax, T1 or DSL modems, stopping when that equipment powers a new circuit off local power.
Or the coax/fiber from the street to the first modem.

Like I said they make cat 5 and even cat 6 that is crush resistant and for any AHJ I know meets the 'barrier' requirement in 725.136(B)
 
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ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Reminds me of the days of adjusting the rabbit ear antenna on the TV "just so" to get the best signal. Sometimes, you had to not let go of it because your body contact improved the reception! 🤪
I still have to do that for over the air reception. The difference is in what lower quality digital signal looks like vs analog. With analog "close enough" works but not so for digital.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Just take a peek in your network closet, look at the power supply for your network switch or router, dont accidentally unplug your office network, do you see anything that says class 2 on it?
That would be a art 725.121 (A)(2) class 2 power supply.
A communications circuit as defined by article 800, I think of like 'service conductors' they originate from a provider, enter the building then go to all the customer owned equipment such as old landline phone, fax, T1 or DSL modems, stopping when that equipment powers a new circuit off local power.
Or the coax/fiber from the street to the first modem.

Like I said they make cat 5 and even cat 6 that is crush resistant and for any AHJ I know meets the 'barrier' requirement in 725.136(B)
As far as I know there is no cable on the market that meets the requirements in 725.136(I)(1) or (2). The cable that is used inside MC for 0-10 volt dimming controls is specifically listed for that purpose.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
As far as I know there is no cable on the market that meets the requirements in 725.136(I)(1) or (2).
(2017) 725.136(I)(1)(b) includes the term "metal-sheathed" cables, which strikes me as a general term, not referring to any specific Chapter 3 wiring method, unlike the other options ("metal-clad, non-metallic sheathed, or type UF"). So how about an armored Cat5 cable inside a raceway with individual power conductors? That would seem to qualify as "metal-sheathed" to me.

E.g., to pick a random brand:


Cheers, Wayne
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
(2017) 725.136(I)(1)(b) includes the term "metal-sheathed" cables, which strikes me as a general term, not referring to any specific Chapter 3 wiring method, unlike the other options ("metal-clad, non-metallic sheathed, or type UF"). So how about an armored Cat5 cable inside a raceway with individual power conductors? That would seem to qualify as "metal-sheathed" to me.

E.g., to pick a random brand:


Cheers, Wayne
I believe it was written that way to permit both MC and AC cables, but I see no reason why armored CAT5 would not be acceptable.
I kind of see the same issue where they use the term non-metallic sheathed, without actually specifying Type NM cable.
 
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