I'm trying to bury cables for my garden. The requirements are to have 12v power for a water pump 30-40 watt (2.5 amp), network connectivity for sensors and a webcam. I want 4 stations at opposite corners – the maximum distance is about 600 feet to the house from a station. From what I've read maximum distance for ethernet is 100m or about 300ft.
I've also been reading about lightning surges and grounding cables. Fiber seems less susceptible to interference and lightning strikes and no 100m distance limitation like ethernet. I know once power and network connectivity is there the camera can plug into that. I'll need another cable for power to drive a water pump.
One person said use flexible PVC conduit so there are no joints underground – should I even use conduit or just buy direct bury cables?
Should I consider some hybrid network system like RS485 or something or just go with fiber?
I've read dual separate conduit if power and data but if fiber and power together in the same conduit this should be OK?
What type of wire would you use for 600 feet 12v 30-40w?
Any other suggestions as to how to achieve what I'm trying to do?
Best Answer
You will want to limit the voltage drop in your DC distribution wiring to 5% or less of the 12V. That would be equivalent to a 0.6V drop. An online wire size calculator suggests that for 600 feet at 3A that you would need to use 1 AWG copper wire.
Cost of that size wire suggests that you may want to consider distributing the AC mains voltage instead and converting to 12VDC at the load points. The reason being is that the amount of voltage drop in the wiring follows the amount of current through the wire. 30-40W at a line level voltage results in less than 0.5A down the wire and 5% voltage drop at 120VACrms makes room for a larger allowable voltage drop than the 0.6V at 12V. The net result is that a much more reasonable wire size can be utilized.
If you use optical fiber cables they could be in the same conduit as DC cables. You may want to separate them from AC mains cabling just because it seems like a good idea to keep AC mains by itself.