Subscriber Discussion

EMI Evidence On UTP Run With AC?

UI
Undisclosed Integrator #1
Feb 18, 2017

Just curious about this because I recently lost a quote for a new house, alarm and IP cam system, due to the other guy being more cost effective.   I did some other wiring there, so when I did the rough-in the other guy had already been through and had run all the CAT5 for the cameras with the electricians wiring, same holes and all, for lengths up to probably 50 or 60 feet.  One spot had a wire literally wrapped around 3 20A wires from floor to ceiling, guessing to save a couple of the electrical staples he used.   Other places it was stapled on top of the AC wires.  Wanted to know if anyone has seen real life problems from such methods, video drop outs or whatever.  From what I have read, seems to be unlikely it will cause issues?

U
Undisclosed #2
Feb 19, 2017
IPVMU Certified

You can totally get away with running power and cat 5 ethernet side by side.

Until you can't, that is.

And it's hard to tell when that is exactly.  Some things that seem to have an effect IMHO are:

  1. The distance that the two lines run parallel. (Longer=worse)
  2. Ethernet type (Gig ethernet worse than fast ethernet)
  3. UTP vs STP (UTP=worse)
  4. Devices being powered by the AC

This last one, again IMHO, can have a huge impact.  Depending what's being powered on the line, the power can get all sorts of high-order harmonic noise on it which intern can interfere more than the lower tonic frequencies.  For example, an incandescent light might be ok but led or fluorescent might kill it.

Since you can't be assured what will be run on the line, I think you are right to be wary.

Although I wouldn't do it, I wouldn't bet against it working.

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Michael Silva
Feb 19, 2017
Silva Consultants

Performance issues aside, I would think that this would be a violation of the electrical code. I would be surprised if the electrical inspector would let this one slide if he or she observed it during an inspection. (Not suggesting that you point it out.....:)

 

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U
Undisclosed #2
Feb 19, 2017
IPVMU Certified

Q: What is the proper separation between communications cabling and power conductors?

A: ANSI/TIA/EIA-569-A section 10.3.1 states that the co-installation of telecommunications cable and power cable is governed by applicable electrical code for safety. For minimum separation requirements of telecommunications cable from typical branch circuits (120/240V, 20A), Section 2 of Article 800-52 of the ANSI/NFPA 70 1999 National Electrical Code specifies the following:

"Communications wires and cables shall be separated at least 2 in. (50.8 mm) from conductors of any electric light, power, Class 1, non-power-limited fire alarm, or medium power network-powered broadband communications circuits."

There are 2 exceptions that involve various means of isolating the two:

"Exception No. 1: Where either (1) all of the conductors of electric light, power, Class 1, non-power-limited fire alarm, or medium power network-powered broadband communications circuits are in a raceway or in metal-sheathed, metal-clad, nonmetallic-sheathed, Type AC or Type UF cables, or (2) all of the conductors of communications circuits are encased in a raceway.

Exception No. 2: Where the communications wires and cables are permanently separated from the conductors of electric light, power, Class 1, non-power-limited fire alarm, or medium power network-powered broadband communications circuits by a continuous and firmly fixed nonconductor, such as porcelain tubes or flexible tubing, in addition to the insulation on the wire."

This separation is required for safety purposes only. For installations where additional separation is possible, chapter 21, page 26 of the 8th Edition of the Building Industry Consulting Services International's (BICSI) Telecommunications Distribution Methods (TDM) Manual states:

"A minimum clearance of 61 cm (24 in.) between electrical power cables and telecommunications cables is recommended."

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UI
Undisclosed Integrator #1
Feb 19, 2017

Thanks for the info!  I did ask an electrician I work with quite a bit if this is against code (Canada), but he told me it's not, just shouldn't be done of course.

U
Undisclosed #2
Feb 19, 2017
IPVMU Certified

Sometimes EMI in Canada can't be avoided :)

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UI
Undisclosed Integrator #1
Feb 19, 2017

Wow, that was definitely an interesting read! 

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