Cable type to use when passing parallel with mains lines

[Darren DeBattista 0]

Hi,

 

I'm going to install a CCTV system in my apartment. Problem is that I already have made all the tiles, plastering and finishes and hence, the only solution I have to pass a wired CCTV without some hard labor is to pass the video cables parallel with the lightning cables through the conduits I made on the roof for the lightning. SO the video cable will actually be touching the 230VAC lightning cables.

 

I have made some search regarding using coax vs UTP cable (with baluns). Problem is that I find some contradicting data with some saying coax is better for interference due to shielding while others saying UTP is better for noise cancellation. Also most of the data I find is related to long distance.

 

Some details regarding my installation.

 

- My installation have a maximum of 30m from the DVR to the camera.

- The DVR is either an AHD type or an Onvif CCTV DVR.

- In the lighting conduits in the roof, I only have the PE, Neutral (N) and return conductors. There is no

Live (L) conductor (live passes through conduits below the tiles) and hence, current will pass parallel

to the video cables only when light is switch on.

- I only plan to use low power LED lighting connected to the wires passing parallel to the video wire

(although LED bulbs usually uses switching regulators which introduces some noise in the cables).

 

I'm an electronics engineer so you can go in some depth regarding the details. I have never worked on CCTV systems so I have no experience to help me to get to a decision on what cable is best to use.

 

Anyone can help me please? Is it even possible to obtain a decent picture with such an installation or a wireless system is absolutely necessary in my case (I was excluding wireless due to cost). WOuld a UTP cable with baluns help (maybe also use parallel conductors from the UTP cable)?

 

Thanks alot!

[rossko 0]

How about STP or FTP - shielded "UTP". You ground the shielding at one end only, allows it to work as shield but prevents earth loops. Only use one pair for signal, there is no benefit in doubling up. But that does leave you spare pairs to carry camera power - you've not mentioned where that fits in.

 

However, most national wiring codes insist on physically segregating signal cables from mains power wiring. No possibility of adding a partition in your conduit? Using weatherproof cable cable-tied to the outside of the conduit?

[the toss 0]

I wouldn't have thought you would be allowed to run your cable in the same conduit as your electrics

[Darren DeBattista 0]

Hi rossko,

 

Thanks for the reply. Regarding the power, I was going to use a siemes cable in the case of a coax cable or else passing power through the UTP cable as you said.

 

As for the waterproff cable, cable tied to the conduit; my wiring is internal. I have maybe 6m running on the outside than the remaining 25m running inside my apartment (my apartment is a bit elongated). Also the roof conduits were passed on the floor of the apartment on top of mine so they are not accessible.

 

Using shielded UTP could be an option too (I assume the shield would be connected to PE to shield noise originating from the mains cable). Only concern would be flexibility of the cable to pass 2 of them through a single 20mm conduit (although the same thing could be said about an RG59 seimes cable). An advantage of using UTP / shielded UTP would be of having extra conductors also for a pick up or to use the entire cable if the cameras are changed for IP version.

 

One other option that came to my mind was that of passing the cable in the corner between the roof and the side wall and maybe (some day....) hide them with coving (could also use this option with the UTP cable_.

 

As you can see I'm quite confused, with a lot of options but few knowledge about the outcome in order to make a decision. Most probably, the best option would be a UTP cable passed in the corner behind coving, but was hoping to not have to make coving just to hide the cables.

[Darren DeBattista 0]

Hi the toss,

 

Ideally, its never done like that. But since my cable length would be relatively short (max 30m), I was hoping that the interference would be small and acceptable. My problem is that I don't have experience with CCTV installations and I was hoping that someone have done something similar and could guide me.

 

Thanks

[the toss 0]

How about STP or FTP - shielded "UTP". You ground the shielding at one end only, allows it to work as shield but prevents earth loops. Only use one pair for signal, there is no benefit in doubling up. But that does leave you spare pairs to carry camera power - you've not mentioned where that fits in.

 

However, most national wiring codes insist on physically segregating signal cables from mains power wiring. No possibility of adding a partition in your conduit? Using weatherproof cable cable-tied to the outside of the conduit?

 

 

A few points -

** there is no such thing as shielded UTP. UTP stands for UNSHIELDED twisted pair. You cannot have shielded unshielded twisted pair.

**Earth loops are not a consideration. The signal is of a balanced configuration and does not use the shield to carry the signal. The shield can be earthed at each end.

** There is no benefit in doubling up the pairs for signal transmission because it WONT WORK if you do

 

@ Darren - from your first post it is plain to see that you understand the relationship between current and EMI. If I had to choose I would use Shielded twisted pair. This will give you the benefit of the EMI shielding as well as the common mode rejection benefits of the twisted pair. Good luck!

[Darren DeBattista 0]

Hi the toss,

 

Thanks for your feedback. It makes sense to use a shielded twisted pair as you said.

Could the cable have multiple twisted pair? This could give me the advantage of passing the camera's supply too (24VDC).

Also, I'm reasoning that a balun to for impedance matching is anyway a must, am I right?

 

Thanks

[jeromephone 6]

First point is the most important no code in Us would allow mains power and low voltage to be run in same conduit. Potential danger to equipment and persons. Once you figure out a way to separate the two either by a barrier or certain distance from the main then you can figure out the rest. Why not cat6 or 5 with IP cams and POE

[the toss 0]

For twisted pair a balun IS a must (unless it is an IP camera)