CCTV Grounding

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big john

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Location
Portland, ME
I'm running a CCTV system that has several exterior cameras as well as an underground run. Like an idiot, it just occured to me today that it'd probably be a good idea to have surge protection on these lines. The code seems pretty quiet about CCTV and I hate to admit I haven't a clue how to proceed on this part.

What's the standard proceedure for grounding/TVSS/lighning arrestor for coaxial cable? Should I try and apply article 800? Is it even necessary when all the cable is in conduit?

Thanks.

-John
 
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Volta

Senior Member
Location
Columbus, Ohio
820.1 shows that the Article 820 covers RF signals distributed on coaxial cable. Normal CCTV uses line-level signals, so not subject to 820, IMO.

Still good to keep the lightning surges outside, though. An optical coupler is a good means of isolation, not that cheap, but less than fiber tranducers.

You can use grounding blocks, but might find some stray currents riding along.
 
don_resqcapt19

don_resqcapt19

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Location
Illinois
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retired electrician
What article does cover this type of installation? It does not fall into any of the Chapter 8 articles and it doesn't really fit in Article 725.
 
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Volta

Senior Member
Location
Columbus, Ohio
don_resqcapt19 said:
What article does cover this type of installation? It does not fall into any of the Chapter 8 articles and it doesn't really fit in Article 725.
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None that I could ever feel sure of. The cable is usually a CM, or CMP, and as it communicates images from one location to another, Art. 800 isn't unreasonable, but it's sure not cut-and-dried.

The associated power typically is a 725 Class 2, and run in the same paths, but don't think the coax is technically subject to the NEC. :mad:

I pretend that it is 725 anyhow, usually. :roll:
 
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cochise7969

Member
Grounding? I've never installed any grounding for my cameras. My power supplies have fuses so if there's a problem I just replace the fuse. Depending on how many cameras you install I either install a 4,8 or 16 channel power supply.
 
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big john

Senior Member
Location
Portland, ME
cochise7969 said:
Grounding? I've never installed any grounding for my cameras. My power supplies have fuses so if there's a problem I just replace the fuse. Depending on how many cameras you install I either install a 4,8 or 16 channel power supply.
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Cochise, my concern isn't the power supply because that is fused. My concern is that I will have these cameras connected to an expensive DVR and flat screen television (not to mention the cameras themselves). I'd be mighty sorry if a spike on the coaxial cooked one or the other. I don't know if the DVR grounds the coaxial braid already or not. I'm new at this. I just want things to be copacetic.

-John
 
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jonelam

New member
CCTV Grounding

I am running into this exact same question... I have 3 buildings with direct burial coax cable for CCTV video transmission and I have already had some cameras burned out and ports on the DVR blew due to a close lightning strike.

I have purchased Ditek Arresters to install at each end of the buried coax and the Ditek Arrester has to be grounded.

I am looking for the best way to ground the Arrester at each of the 3 buildings and was told by another source that: Indepenent Earth Grounding Rods could be driven into the ground at each of the 3 buildings with the grounding wires from the Ditek Arresters at each location tied directly to the earth grounding rods... This makes sense and would be the simplest options but I have seen many other posts stating that multiple independent earth grounds are BAD and dangerous... I am not sure if these apply to the scenario I am doing with only grounding the arresters for the CCTV coax???

Any thoughts on this are greatly appreciated...
 
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nhfire77

Senior Member
Location
NH
jonelam said:
I am running into this exact same question... I have 3 buildings with direct burial coax cable for CCTV video transmission and I have already had some cameras burned out and ports on the DVR blew due to a close lightning strike.

I have purchased Ditek Arresters to install at each end of the buried coax and the Ditek Arrester has to be grounded.

I am looking for the best way to ground the Arrester at each of the 3 buildings and was told by another source that: Indepenent Earth Grounding Rods could be driven into the ground at each of the 3 buildings with the grounding wires from the Ditek Arresters at each location tied directly to the earth grounding rods... This makes sense and would be the simplest options but I have seen many other posts stating that multiple independent earth grounds are BAD and dangerous... I am not sure if these apply to the scenario I am doing with only grounding the arresters for the CCTV coax???

Any thoughts on this are greatly appreciated...
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Sure you can drive your own rods....but you still have to bond them the the existing GES.
 
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jrdsg

Senior Member
Location
Vancouver, Canada
ground loops

ground loops

coaxial cable for cctv can't be grounded at both ends, since this can induce current between the two ends on the shield [there's often a potential difference between the two ends]. since the video signal itself is only 1v Pp it doesn't take much to overwhelm it.

this can also occur where the camera is powered by an lv transformer at a location remote from the head end equipment.

there's remediation equipment available [such as optical couplers or ground isolation transformers] but these can add significantly to your input costs.

we're installing mostly ethernet cameras on new installations, often with low-cost fiber trunking or WIFI bridges between legs that effectively isolate different sections of the system from each other. ethernet cameras are also available in much higher resolution [1.3 megapixels and up, at least four times the resolution of high-res analog surveillance cameras at 640x480 or 720x480]. we recently did a job with 5 MP cameras that record at full hdtv resolution. you can cover a larger area or get way more detail with one camera.
 
tom baker

tom baker

First Chief Moderator
Staff member
Location
Bremerton, Washington
big john said:
The code seems pretty quiet about CCTV and I hate to admit I haven't a clue how to proceed on this part.

-John
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Article 820 , although the title is misleading. Where the coax enters the building, install an impulse supressor, transistion to the interior listed coax. With the inpulse supressor create a single point ground, see 250.94
 
StephenSDH

StephenSDH

Senior Member
Location
Allentown, PA
cochise7969 said:
Grounding? I've never installed any grounding for my cameras. My power supplies have fuses so if there's a problem I just replace the fuse. Depending on how many cameras you install I either install a 4,8 or 16 channel power supply.
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Your fuse won't protect any of your equipment from a lightning surge. Intersystem grounding, with surge arresters is your best chance of you equipment surviving a strike.
 
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nhfire77

Senior Member
Location
NH
I will reiterate, I have used Ditek surge equipment with out fail. So far no equipment down stream of a Ditek device surge damaged. The Ditek equipment i find smoked, but thats why they are there. The company is based out of Florida, they know lightning there.

No, I do not work for them, I just really like there equipment and, its a great up $ell in every LV job.
 
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cadpoint

cadpoint

Senior Member
Location
Durham, NC
nhfire77 said:
.... So far no equipment down stream of a Ditek device surge damaged. The Ditek equipment i find smoked, but thats why they are there...
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Ain't everything a $100 dollors now. Santa's Coming ... :roll: DTK-4VP

I thought they did that at every CCTV drop on the service side?

Can I make due with a inline and then standard branching?
 
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