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.
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Robert Green wrote:

Hi, If I were you, I'd go wireless. No cables to worry about. Any particular reason you want wired?
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Yes.
Thanks.
-- Bobby G.
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Robert Green wrote:

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.
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<stuff snipped>

volts
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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.
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Robert Green wrote:

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.
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<stuff snipped>

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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.

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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.

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them.
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.
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*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.
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famous
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 . . .

company
and
Thanks - I've heard of them. I'll give them a look-see.
-- Bobby G.
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wrote:

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.
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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.
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<stuff snipped>
<<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.>>
Are we talking about the stuff with the rotating nylon wire? I've only got an electric one and I don't think it would dig much of a trench because it can hardly trim weeds it's so anemic. I assume the gas ones have much more HP and perhaps a different cutting head. Would it dig enough of a trench to be able to lay 2" drain pipe as a conduit? If the wires are all encased, I'd be less concerned about them heaving up and getting caught in the mower blade.
-- Bobby G.
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wrote:
<stuff snipped>
<<I have no idea how 18GA speaker wire is gonna work for an intercom>>
I do, it will be just fine.
<< no intercom made in the last 40 years works on 8 ohm speakers.>>
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.
<<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.>>
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.
<<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?>>
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.
<<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).>>
That sounds like an interesting idea if my underage labor force doesn't work out. I've seen that sort of machine on TOH. Not sure it would work in this mix of clay and rock, but I will certainly look into it. IIRC, that machine's best feature is its ability to run under driveways and walkways that don't lend themselves to open trenchwork. I am not facing that sort of problem. I've got an unimpeded run of dirt to the proposed location of the lamp post.
<<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'm probably going to cheat and pull the wire through while the conduit is still above ground. I don't anticipate much trouble that way although I agree once it's in ground, pulling any more cables or replacing any that go bad will not be a cakewalk.
<<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.>>
In the DC area, there have been some serious wireless issues with garage openers, car key fobs and other gear. There are several military installations that have been working on jamming IED's - wireless IED's - and every once in a while, RF gear mysteriously stops working around here. With all the RF spectrum reallocation occuring recently, I'm not sure what low-power "must accept all interference" devices will stay working throughout the next five years. Apparently, when the local garage door openers began to get "stepped on" the Air Force said "tough nougies" we own the frequency, go pound sand.
When the signal absolutely, positively has to get there, wired is the only way to go. At least IMHO. Wireless video is especially crappy around here and none of the cheap 2.4GHz gear works well enough to consider unless you build your own hi-efficiency yagi antennas. I've done that and can testify that they ain't pretty and have seriously low SAF. The upside was that I was able to catch the local crackhead who had been breaking into cars by installing a wireless cam inside my van.
So I agree: wireless has its place, just not in this application. The wireless CCTV gear that *does* work well enough for this app requires a license to operate and costs real $$$. If renting a trencher could make or break this project pricewise, effective wireless is way, way out of the picture.
I am trying to limit the value of any items mounted on the lamp post in case someone decides to run off with it or run into it with their car. Don't laugh - the next door neighbor's house is at the end of the road at a T-intersection and they already have had a car plow into their living room. The worst part is that the cops that came weren't even surprised. They said people run into houses all the time, especially around steep curves or at T intersections where the road just runs out.
The little board cameras I am using cost less than 12 bucks (!!!) from Supercircuits and are more than adequate for the task. They are so cheap that I am planning to mount one in each pane of the lamp to give me a four way view. They'll be feeding into a 16CH MUX that I got for $45 on Ebay that used to sell for $600 just a few years ago!!!
I might look into using baluns to reduce the four RG59U cables that would require to a single CAT 5 run becauseCCTV balun components have gotten incredibly cheap in the last few years, but the truth is, doing that would probably cost the same as running four discrete coax cables.
I might pull a CAT-5 run to the lamp post just as insurance and to allow me to add other gear I haven't thought of yet like a sensor to determine if the gate has been opened or a PIR to detect when people approach the lamp post. With a little early warning I might finally be able to catch the FedEx man before he can rush up to the door and leave a door tag saying "we missed you." (-: What was I saying about "mission creep?"
Thanks for your input. I'll be googling sprinkler installation tools shortly.
-- Bobby G.
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