I have a bldg. where the coax home runs were run before the big gray electrical service lines . The electrical lines are running parallel with my coax home runs where they leave the corridor to end apt. to exit at end of bldg. My question is , would a 3" pvc electrical conduit cut in half and duct taped around coax protect it from the electrical service lines. They already sheetrocked the apts. , just haven't done the corridor yet.
coax vs electrical homeruns
- Thread starter cobb
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zbang
Senior Member
- Location
- Roughly 5346 miles from Earls Court
You don't need physical protection and the PVC won't provide any electrical isolation, but then you probably don't need it. Leave things alone unless there's an actual problem.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
I think he is more concerned about noise jumping from what he is calling the service wires to the coax.
I would guess the coax is for cable TV service. Coax is fairly noise immune. I would not be all that worried about it unless they wrap the coax around the electrical wires. Kind of surprised in an apartment building that they would run open wires for electricity. Normally they would be in some kind of conduit. Not that it would always be required, but generally that's the way it's done. I suppose if it's a small enough building it could be done in Romex.
I would guess the coax is for cable TV service. Coax is fairly noise immune. I would not be all that worried about it unless they wrap the coax around the electrical wires. Kind of surprised in an apartment building that they would run open wires for electricity. Normally they would be in some kind of conduit. Not that it would always be required, but generally that's the way it's done. I suppose if it's a small enough building it could be done in Romex.
If that were the case, I don’t think he would have brought up PVC as a proposed remedy.
petersonra
Senior Member
- Location
- Northern illinois
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- Semi-retired engineer
Perhaps he does not know any better
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
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- Electrical Contractor
As you can see, neither necessary nor beneficial.
The aura or noise that emanates off the apts. 1.5" feed line , disrupts the cable signal and causes issues for whoever is watching tv ( digital signals) . I put the lines there before the electrico hombres put their main home runs in , guess I should have asked where they were going to put them. I really hate putting in the coax home runs before the electric is in. But I was told that it needed to be as soon as possible. I did cut the pvc in half and put it on them , I checked the next bldg. to see what they did . They literally ziptyed to my home runs. Took pics will send to the people I contract from.
I've been running cale for 27 years. Yes I do know how electrical lines ( if run parallel ) within 3 to 6"s effect the signal.
petersonra
Senior Member
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- Northern illinois
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- Semi-retired engineer
My apologies. Your profile does not say anything about being an electrician, and the way the post was phrased did not suggest electrician to me.
Incidentally there is no three or six inch rule in the code. The code just does not care how much separation as long as they are separated.
It's possible that there might be some noise generated on the electrical lines that potentially could propagate over to the coax, but it's not real likely. Possible though.
PVC has zero electromagnetic attenuation properties.
If you believe that proximity to power cables will disrupt the signal, you should probably run quad shield whenever there’s a possibility of this situation.
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
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- EC
I worked for cable companies almost as long back in the analog days. If there was any interference you would see it. I saw cable directly ty-wrapped to the "big gray electrical service lines" from the splices on top down to the meter and any other place where too lazy to support the cable properly. I can tell you though, there was never a problem from proximity to power wiring.
If there is some kind of interference the solution is to use a cable with one or more additional shields. But the cable company should have figured that out already if there is a problem in your area.
-Hal
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Did you ever work a bldg. according to the prints and think , "wow , it must have looked good on paper" .?
winnie
Senior Member
- Location
- Springfield, MA, USA
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- Electric motor research
Are you actually seeing a problem or trying to prevent a potential problem?
My _guess_ is that the primary potential for causing a problem is unbalanced electrical current flowing in a feeder, with 60 Hz current coupling to the coax and doing things like causing signal drops by saturating the RF signal path with what is essentially DC.
If these apartments are wired to present day code, there shouldn't be any unbalanced current in the feeders.
Jon
My _guess_ is that the primary potential for causing a problem is unbalanced electrical current flowing in a feeder, with 60 Hz current coupling to the coax and doing things like causing signal drops by saturating the RF signal path with what is essentially DC.
If these apartments are wired to present day code, there shouldn't be any unbalanced current in the feeders.
Jon
petersonra
Senior Member
- Location
- Northern illinois
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- Semi-retired engineer
I'm an engineer. I don't actually "work".
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
In all my years I have never seen a problem caused by coax in close proximity to power.
Tell me a little about this installation. I assume these are individual RG/6 type "drops" originating from taps in an electrical or equipment closet that run down the hall in the ceiling to the individual units? Each drop either feeds a splitter or maybe only one wall jack? And it's those drops that you are concerned with?
-Hal
Yes , the actual problem is a " hum " sound.
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
Since the cable signal is digital, any 60Hz induced from the electrical wiring would not be heard as a hum since the interference is analog.
I once had a situation in a condo development that had a feeder running through it with taps in pedestals periodically to serve the units. The pedestals were located out on the street with the POCO transformers. The complaint was 60Hz hum bars rolling through the picture on all channels. The problem turned out to be that the feeder running underground from tap to tap was only grounded in a few places which allowed a large neutral current to be carried by the cable sheath from one end of the development to the other. Grounding each tap to the utility transformer ground solved the problem. What happens in the analog world is that the cable carrying a current on the sheath actually made a pretty good modulator and modulated the analog TV carriers with the 60Hz. And no, it did not affect the audio which is FM.
But back to your case, I can't see how noise induced on your coax drops could cause a hum in the audio. I'm assuming here that what you are installing is just normal CATV, not something that is fed from CATV then converted from digital to legacy analog like they might do for a motel or nursing home with cheapo vintage TVs.
-Hal
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