electrical question

[kerosenedrvr]

I installed an electric gate operator at the end of my 350ft driveway. I currently use a solar charger and battery. I want to run "real" electric so that I can install a solenoid lock, low voltage lighting, an intercom, lighted keypad and camera.
My question is: what size wire should I use? I also want to install video and intercom wiring. Is there an issue with RF interference if all wires share the same pvc conduit? If so, what is the horizontal seperation I should use? Thank you in advance for your replies.

[Pat]

You can do everything you want with solar electricity and no long wire runs but to be practical you need a low power camera or just power it up by remote control when someone uses the intercom (RF intercom.)

If you want to hardwire it you are right to be concerned about interference in a long run of signal wires with power wires. To reduce the coupling effect you should used twisted wires. You don't have to look for twisted wiring, you can twist two wires together your self. The hot and neutral should be twisted together. One way to do that is to stretch the wires out along side each other, tie the one end of the pair to a fixed object,and attach a drill to the other end of the pair. You can run the drill to twist the pair but a long run presents procedural problems that can be ameliorated with ingenuity. One way to help do it kink free is to set up a tall ladder and have a helper cradle the pair in their hands loosely up high in the air. This helps do a significantly longer pair without getting so much debris entangled as you might laying the wire on the ground. It will not twist evenly and it is good to take the drill off (be careful the wire will spin like crazy as it relaxes a bit) the one end and put it on the other to twist a while. You need to chuck it firmly and pull back to create tension to get smooth twisting.

The current flow in the neutral and hot wires are equal and the fields in the twisted pair cancel each other in the "far field." the green (ground wire) can just run straight beside the twisted pair as it ordinarily does not conduct current except in emergency conditions.

For a really long run you might need to splice lengths of twisted pair together (or look harder for premade twisted pair in a suitable gauge.)

You will need to find the current draw or power rating of all devices you intend to run on this circuit befor the wire size can be selected. Note that you can stay with the battery operated opener and use a "tapering" type battery charger to maintain the battery or to assist the solar charger. This will reduce the A/C load on the wires going to the gate considerably.

Don't use cheap coax for the video. Use low loss coax with good (double) shield. I do not recommend foam dielectric even though it is cheaper and is low loss because it is bad about absorbing mioisture and deteriorating rather quickly. Do not try to go direct bury, use conduit(s). Do run a HD nylon cord (like parachute cord) with the wires in the conduit(s) but do not tape or in any way conect the cord to the wires. This cord will allow you to pull another wire in the future should it become neccessary (CHEAP INSURANCE.)

For the long coax run I'd look in a catalog or enlist a techie's help to select a good coax. You might be better served to use "full size" coax instead of miniature. Something the size of RG-8 maybe but better to look in a wire company's ratings I may not know the best choice as I haven't done too much coax work in last 10 years except short runs for TV stuff.

As I am way past my bedtime I may have missed something obvious to an alert person but I think I hit several points of interest.

Pat

[kerosenedrvr]

thank you very much for the professional advice

[Pat]

Hmmm, I forgot to mention that with a long run like that it is still a good idea to run the low level signal wires (intercom and such) well separated from the power wires, even with shielded wires and twisted wires for the hot and neutral. Shielding isn't perfect and if you run the wires parallel in close proximity for a great enough distance you will couple in an objectionable degree of AC hum into your intercom. Separate conduits is safer. They don't have to be very far apart. Direct bury AC power wires aren't such a bad deal but avoid direct bury for the TV, intercom, etc. With direct bury you can't leave a string in to pull extra wires later. You can bury extra wires but how many of what type? Better to have a conduit sized to allow pulling future wires.

Do you have gophers? Gophers will ruin some of the direct buriel power wires. Yet another reason to use a conduit.

Pat [img]/forums/images/icons/smile.gif[/img]