I've read where it is not advisable to run CAT cable along side AC power lines, and I assume this is because of the inductive effect. Because of the design of my attic, I've had to run my CAT6 cables parallel and very close to several pieces of Romex for a distance of about 8 feet. I've never noticed any issues in the several years my camera system has been up. Where would one see the effect in doing this?
AC inductive effect
- Thread starter dryfly
- Start date
sebastiantombs
Known around here
That would most likely happen if the AC line had a heavy load, like an air conditioner or microwave or convection/toaster oven. The twist in CAT cable does have some cancelling effects for induced noise/voltage and, if the load is low enough like general lighting for example, nothing will actually be noticeable. It's still a good idea and best practice to avoid running parallel and within less than six inches of power cables even in a residential setting. In industrial settings metallic conduit is the way to go.
Probably more so in analog camera systems with BNC / siamese cable (video + 12VDC), and if so, usually with 60Hz hash.
The CAT cable's design both mechanical (UTP) and electrical/electronic (differential pairs) mitigate all but the worst of interference issues, especially short distances as yours.
Thanks for the input. Lots of various Romex runs in the area of the CAT cable, and some do have high current, A/C's etc. If I'd thought about it I could have ran the CAT through a piece of EMT conduit for shielding. It would be a fair amount of work to do it now, and besides as I said, I'm not seeing any evidence of interference.
Yeah, I wouldn't try to fix it if it ain't broke...at this point it falls into my ever-growing category of "...maybe next time." 
tangent
IPCT Contributor
- Joined
- May 12, 2016
- Messages
- 4,434
- Reaction score
- 3,679
It's more a matter of how noisy a particular load is rather than how big the load is, both are potentially relevant. Things like dimmers, light ballasts, or perhaps an ECM motor can actually be some of the biggest sources of noise.
This sort of thing tends to matter more in commercial environments where you have dozens of cables in close proximity to one another and sources of interference.
if it's not broke don't fix it.
I ran 100ft of CAT6 in the same underground conduit as 10 AWG electrical. Haven't wired in the electrical yet, but we'll see if it still works then.
If not, the electrical should allow me to do ethernet over power.
If not, the electrical should allow me to do ethernet over power.
tangent
IPCT Contributor
- Joined
- May 12, 2016
- Messages
- 4,434
- Reaction score
- 3,679
In addition to potential interference, the other reason this is frowned upon is scenarios where something goes wrong and 120V+ ends up connected to your Ethernet wiring.
Last edited:
Ah, so many great minds on this forum.....and at least one with better grammar!
Flintstone61
Known around here
Thats probably why i have 60hz sine wave bars ( Whatever they are) drifting down my overview Camera screen at night. Once the cable gets into my office ( concrete ceiling & 4 concrete block walls) There are 120V conduits criss-crossing the ceiling and walls. Used to see it on a couple of the CCTV cams. still see it on a couple of the IP Cams. ( only at night)
Back in the early 70's when testing traffic signal cabinets before installing in the field, we'd burn-in the controllers (with microprocessors or micro-controllers, etc.) for 30 days, inspect the workmanship, adherence to specs, etc.
A very unsophisticated but effective way to put EMF spikes on the AC power line feeding the cabinet was to energize/de-energize just plain, old fashioned 120VAC relay coils from that same AC line. The back-EMF placed on the line by the collapsing field when the coils de-energized could actually cause an improperly filtered and suppressed signal controller to go from a green traffic signal display in the field directly to red with no yellow display for 3 to 4 seconds in between or shorten that yellow display to 1 second...not good!
Properly designed and constructed traffic signal cabinets had incoming filters and suppression on the utility company supplied AC power as well as R-C networks (Quencharc® Arc Suppressor/Snubber Network) for EMI/RFI suppression wired across the coil of every AC relay and mercury contactor. DC relay coils had a diode clamp (usually a 1N4003) across them to protect transistor or bi-polar outputs that drove those coils from damage by that same back-EMF when the coil would energize/de-energize. And of course, the traffic signal controller itself had to have a well designed, filtered and transient-protected internal DC power supply.
Loads to the 120VAC tungsten-filament traffic signal lamps (and later 120VAC LED's) were switched by 3 circuit, modular "load switches", which used an opto-isolated triac for each vehicle signal color of red, yellow and green and pedestrian signal of "walking man" (lunar white walk) and "upraised hand" (Portland orange don't walk). Early load switches used dual SCR's for each color, one for the positive AC cycle and one for the negative to provide full-wave AC to the field color. By design, the loadswitches would turn the lamps on or off at the AC zero-crossing. This was to reduce RFI but it also prolonged lamp filament life. A 12-circuit male "Cinch-Jones" plug at the rear of the load switch allowed for a quick changeout of a defective load switch. The signal controller's output to these load switches was a 24VDC level with "True" (color ON) being at DC logic ground level and "False" (color OFF) being a pull-up to +24VDC.
My point? There's plenty of RFI/EMI noise inside that medium refrigerator-sized traffic signal cabinet to make a poorly designed circuit act up and malfunction with just plain old relay coils and mercury contactor coils. Switching large AC loads, especially inductive loads, can present its own considerations for design and implementation.
^ 100% Illegal and unsafe and will damage / kill someone down the line.
So how do these sources of noise show up on the cameras? Visible lines of distortion? Lack of recording?
Depending upon the type of interference and the intensity of the same. It can be seen or heard as wavy lines, bars, odd colors, hum, buzz, popping, strobing, haze / snow, etc. Anyone with the proper tools can detect interference whether that be a 10K oscilloscope to something extremely simple: Radio, Florescent Bulb, Cell Phone, etc.
Keeping in mind RFI vs EMI is not the same but at times result in similar observed behavior / problems.
If a vehicle is leaking any high frequency radiation a common florescent bulb will immediately display the same by flicking. In the same vain if RFI is present if a radio is tuned into a empty (AM - FM) band the common background hiss one normally hears will show case anything from popping, extreme hash / hiss, whirling, as you move to / or away from the generated noise.
Regardless of the above more often than not problems seen at home, in business, in the industry is due to improper grounding.
Whether that be due to ground loop, poor grounding . . .
Poor grounding can be as simple as the ground is a poor conductor: Sand vs Clay
Ground rod not driven deep enough, star washer not used, pole mount is used without a dedicated ground strap to ground rod (not 8' or longer), corrosion, plastic on metal.
CAT cable has (4) twisted pairs, and each pair have a different twist ratio. This not only helps prevent interference from other cables, but also between each twisted pair.
If conduit is not an option, STP (shielded twisted pair) CAT cable & connectors adds another level of protection.
SpacemanSpiff
Known around here
I believe I am aware of the mechanical qualities a washer provides to a physical connection. What advantages does a star washer add to a 'ground' connection?
tangent
IPCT Contributor
- Joined
- May 12, 2016
- Messages
- 4,434
- Reaction score
- 3,679
You're thinking more about analog signals.
In the world of ip cameras interference that's significant enough to cause problems would result in packet loss and in turn dropped frames or compression artifacts.
The use of a star washer provides several benefits which are these in no specific order of relevance or importance:
- Mechanical: The teeth of the washer will bite into the material which adds friction and thus reduces the incidence of bolt / screw from coming loose - walking out.
- Grounding: As noted up above because the star washer has bitten into the material there is always a contact point to the body of the frame / wall / poll. Should corrosion develop it will extend the contact / grounding longer vs if it wasn't present as the small teeth of the washer are embedded into the substrate.
Regardless of the use of star washer all of this assumes everything is of quality material. If you use any none SS material you just wasted your time even putting on a star washer.
If you don't add / cover up the grounding point you're just wasting time.Hence the use of dielectric grease / conductive Nygel . . .
Everyday people skip something so very simple and instead of a 10~20 year install its a annual / yearly trip! Keeping in mind there are millions of poles where there is zero grounding wire present and relies solely on the pole?!?!
SpacemanSpiff
Known around here
Thanks fer lernin' me something new!