Burying video/audio intercom to front gate

Can anyone point me to a good site that would prepare me for the task of burying about 50' of video, audio and power cable? Long. and lat. about the same as the President's (as in near Wash, DC) so the soil is rocky clay. Gas lines and water lines are below ground, everything else is above (power, phone, CATV). I want to run a 12V power cable, two or three RG59U CCTV cables and some 18ga speaker wire for the intercom box..

Ground is nice and wet and good for digging, but I've never run any cable outside. I susect the best tool would be to rent a trencher and dig, troglodyte, did. Anyone able to tell me what it's going to cost and if it's even reasonable to consider a post hole digger (which I have) instead of a trencher to do the job?

Am I going to have to go deep enough to have to call MISSUTILITY (if she hasn't been laid off along with everyone else!)?

I assume that anything over a few wires needs to be run in conduit. Is that correct? Are there different kinds of conduit for burial? Do I need to run burial grade cable in conduit or will conduit protect normal interior use cable?

Can I calculate the voltage drop just by observation? (Measure battery voltage at one end and then through the run of wire to see how many volts remain and how much more than 12VDC I need to push through the wire to get

12VDC at the front gate?)

Thanks in advance for any help,

-- Bobby G.

Reply to
Robert Green
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Hi, If I were you, I'd go wireless. No cables to worry about. Any particular reason you want wired?

Reply to
Tony Hwang

Run 24VAC to the gate, and then use a 24VAC to 12VDC converter, i.e. Google "SECUREMAX: AT12015".

For low voltage wiring, you don't need to go very deep, 6-8" and hopefully gas and water lines are a lot deeper than that.

Conduit is nice, to keep the wires clean and together and protected, though low voltage outdoor wiring is often just buried without conduit (i.e. sprinkler valve wiring). I put it inside PVC pipe.

Reply to
SMS

Yes.

Thanks.

-- Bobby G.

Reply to
Robert Green

Is it that long a run that I'll be losing significant amounts of power using DC? I already have a variable voltage switching power supply gizmo I intend to use for the project that uses one coaxial cable to send audio, video and power. It comes with a variable voltage power supply and an adapter on each end to inject and extract the audio and video from the cable.

Will there be a substantial or even significant savings in my electric bill gained by using 24AC and then converting it to DC? Is the conversion done to save power or mostly to deal with the problem of voltage drop over long runs of DC cable? I've seen these devices in CCTV catalogs, so it seems like they are a popular solution. I'd just like to understand the tradeoffs a little better.

Good. I've read all sorts of disaster stories about frost heaving the ground and unburying the wires in some electrical nightmare version of the movie Poltergeist. I just don't want to one day catch the lawnmower up in wires that have unburied themselves.

Conduit's going to add to the cost and complexity of the job, and I'd like to avoid it if burial grade cable is "good enough" to get the job done.

Thanks for your input!

-- Bobby G.

Reply to
Robert Green

*Call 811 to request a utility markdown of the property before digging. I would run the conduit at least 18" deep. In order to measure voltage drop you would need to put a load on the wire. If possible I would run 120 volts out to the location and step down the voltage there. Separate power and communication cables. Use wires rated for wet location use. Oversize your conduits for ease of pulling. Keep your bends to four 90's or less. Use at least PVC schedule 40, but schedule 80 has a thicker wall.

I can't imagine digging a trench with a post hole digger. A backhoe does an excellent job of digging a nice deep and wide trench. When that is not available I use a landscape contractor. They are use to digging holes and their labor charges are quite reasonable. Call around to rental companies to get an idea of trencher costs. It should only take a few hours, but you will spend an entire day picking up the machine, trenching and then returning it. Get a bigger machine then what you think you need. It will come in handy when you hit rocks.

Reply to
John Grabowski

Then that's different. I was assuming you were sending the power separately. Generally it's better to regulate DC close to where you'll be needing it because of the high I squared R losses. But if you can jack up the voltage at the source then that's fine.

Yeah, that's why I enclose my sprinkler valve wirings in conduit or just plain PVC. I had to put in some long runs of wire to valves in the back yard.

I think it would make the job easier. You don't need to use real conduit for low voltage. Use plain schedule 40 PVC which is very cheap. You don't even have to glue it with PVC cement. Use some short brass screws on the couplings. Buy 20' lengths of PVC and you'll only need three of them.

Reply to
SMS

I have no idea how 18GA speaker wire is gonna work for an intercom, no intercom made in the last 40 years works on 8 ohm speakers.

Additionally there are better ways to do the video than modulating a camera onto what, RG59U? For all that work you should just use RG6 quad shield.

I would seriosly just look at getting AC power out to there above the priority of the LV wires. Is there a lamppost nearby to tap off?

If you do insist to make a run out there then I'd use the 1.5 inch black coiled stuff with no joints in the run (what the sprinklers use). No need to trench, just rent the machine that pulls it through the ground at an 8 inch depth (Google how sprinklers are installed).

Pulling wire/coax through any plastic tubing is a hassle, its sticky and binds up easily especially on a run that long. Especially that speaker wire you speak of, that will bind up so tight you'll be lucky to pull it the first 15 feet, believe me speaker wire will bind up solid even on a straight pull, forget a curve. Additionally you wont be able to grease the wire enough with pulling silicone, so you may want to consider installing a valve box at the half-way point as a pull box or even two valve boxes.

I still think you would be better off just running power with UF alone then go entirely wireless with intercom, video, gate control, motion sensors, headlight sensor, vehicle sensor, etc. The reliability/ security of wireless is greatly improved over the last 5 years.

Reply to
windcrest

If you just want to get something below the surface fast and cheap use a gas edger. It will dig a trench a couple inches deep. There are no depth requirements for low voltage. Everything else will be way down so you don't need to get the utlities marked if you just go down a few inches.

Reply to
jamesgangnc

If there was a power savings payoff for going the AC route, I'd go for it, but for a 50' run I doubt it would matter. I just need to be able to adjust the output properly (it's a little slotted dial on the case of the power supply) so I don't blow the camera's electronics. I guess I'll test it with a 12V tailight bulb or load similar to the camera's draw before I plug in the camera.

Around here Comcast is legendary for "surface mounting" their cable by laying cable right on the ground until one of their burial crews can get to it. Sometimes they don't get to it before trauma occurs. I want to have everything ready to do this all at once.

Actually, I have lots of left over central vac tubing that I think will make very nice conduit and eliminate the need to store the excess. Good idea. Thanks!

-- Bobby G.

Reply to
Robert Green

I do, it will be just fine.

I've got a whole set of RatShack units that work quite nicely over speaker wire and I don't believe they're a day over 20 years old. (-: I intend to pop out the components and mount them in a louvered stainless box I have lying around that I know is even older because it was recovered from a fire in 1980! I also have a little mike with a built in amp from Ebay today for $3.65 (shipping included!!!) that I might decide to use as the sending microphone if the RatShack unit doesn't sound clear enough after I transplant it.

Truthfully, sometimes it's to my advantage (and amusement) if Jehovah's Witnesses can't hear me clearly even though I can hear them. The Shack I-com actually runs on 22GA stranded wire, but it's delicate wire and I wouldn't want to depend on it surviving a conduit leak.

RG6QS is way, way overkill for baseband CCTV work. RG59U has been working just fine and I have rolls and rolls of it. I use QS for pumping the incoming broadband CATV feed around the house but it would be a waste of money using it for low-bandwidth black and white board cams.

Doing that means working to code, inspection hassles, potential shock issues and things I'm not willing to get into when I am certain what I have planned will work quite nicely. AC power to the post would only complicate things and add serious expense, hassle and potential lethality to the project. The lamp post is not meant to really function as a lamp - it's there to mostly house all the aforementioned components in something with reasonable SAF. I will probably mount a photocell activated LED or some other 12VDC type of light inside the post to provide just enough illumination to light up a face at night. There's a very powerful streetlight just across the road that provides more than enough illumination.

Reply to
Robert Green

Oops! I can't help myself from asking. I've met the niece of the inventor of the transistor and the great-great grandson of one of the pioneers of submarine warfare by asking. Of course, there have been many more misses than hits.

I found a local (enough) rental place that rents trenching equipment and found a few possibilities:

Ditch Witch 1230

4 HOURS$ 75.00 DAY$ 125.00

Ditch Witch 1820

4 HOURS$ 100.00 DAY$ 150.00

Ditch Witch 3700 DAY$ 295.00

Ditch Witch RT40 DAY$ 325.00

Cable Plow DAY$ 200.00 WEEK$ 700.00

It's hard to tell which model will do the best job. The more expensive the rental, the larger the machine, the more wheels and more things sticking out of them. I'm still inclined to look for a trenching contractor who could zip in and do the job in less time than it would take me to fill out the rental form!

I've been Googling sprinkler installation stories and many first time renters report these machines are heavy, hard to get from the rental store to the house and back, and have lots of surprises for the amateur, my favorite of which was the guy who found a buried clothesline with his rented trencher. Having once sucked an extension cord into a snowblower, it brought back less than fond memories. Another interesting report talked about the small trenchers digging such a narrow trench that they had to be widened by hand. The search continues . . .

Thanks - I've heard of them. I'll give them a look-see.

-- Bobby G.

Reply to
Robert Green

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