Eddy Current
Senior Member
Does anybody no a code reference for this? I no its a no no and can cause interference.
Running MC cable in the same chase as telephone/computer wire
- Thread starter Eddy Current
- Start date
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- Illinois
- Occupation
- retired electrician
It is not a code issue and it is unlikely to cause any interference.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
I agree on both counts, especially for a cable with a metal jacket.
hotwire1955
Senior Member
- Location
- nj
yes it is a code issue 800.133
- Location
- New Jersey
- Occupation
- Journeyman Electrician
If you mean 800.133(A)(2) it says nothing about cables.
Eddy Current
Senior Member
I know that it causes interference in fire alarm cable wouldn't it in telephone and computer cables. I also know that in audio it can cause some undesired static.
So there is no code? Is it just bad practice then?
I also came across this
http://www.neca-neis.org/cqd/index.cfm?fuseaction=showArchiveQuestion&id=2877
So there is no code? Is it just bad practice then?
I also came across this
http://www.neca-neis.org/cqd/index.cfm?fuseaction=showArchiveQuestion&id=2877
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Although many consider it good practice to separate power from low volt cables, there are times it is difficult to keep them away from each other, like when they enter equipment that uses both. They almost always come in close proximity at some piece of equipment.
The use of twisted pair cables for the low voltage equipment greatly reduces the possibility of interference, use a shielded cable and you reduce the risk even more. Most multipair communication cables have individual pairs twisted to prevent inteference between pairs. For audio even nearby radio frequency transmissions can be picked up by the cable and if a voice transmission sometimes you can actually hear the voice transmission on the speakers - twisted pair cables will eliminate this problem also.
I once new a guy that lived near a commercial radio station broadcast tower and he complained about their signal being too strong - he picked up their station no matter where he tuned the receiver. I told him to run twisted pair cables to his speakers and it would help. He did, and had no problem afterward.
What fire alarm system do you speak of?
Just to note, that article you noted does not address the OP question. You were asking of the same chase. This is a very common practice with no ill effects in all but the most unusual situations. The separation of light and power circuits in raceways, enclosures and cable trays is important from a safety standpoint, but not interference.
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Eddy Current
Senior Member
A fire alarm guy told me once that fire alarm cable strapped to emt conduit and run through the same chase causes interference. Is this not true?
Well first of all.... PLFA circuits strapped to EMT is not independently supported, and violates 760.143, and it is hack work. I've see it done all the time without interference, and it looks like crap
Also, no. There is very little if any chance that it will cause any problem. If that were true, just about every fire alarm cable within an inch of a AC circuit raceways might have problems, and they are all over the place. More and more AHJ's are requiring a dedicated raceway or MC for fire alarm circuits anyway, and in most cases makes sense. But standard FPL cable has its place. (this is all my opinion)
Also read 760.136 regarding separation of power and light from fire alarm circuits.
For some reason Audio circuits also cannot be run with PLFA circuits ( 760.139(d) ). Its good practice to keep PLFA in their own raceway if possible. Occasionally burg CCTV and access control is mixed in. That's not the end of the world, but it makes having to work on non fire alarm circuits in the same raceway as fire alarm circuits that more complicated.
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