AS I built the track, it was raised on Hardiboard and had no dirt. I ran the wires as needed to feed the power sectors of the track. There are about 100 different sectors for the track layout and each of these had individual wires to feed the voltage to the track. The wires feed power to the track at 18V. The wires are 12 guage to feed the correct voltage and amps to the track. I used THHN type wire which is rated for outdoors and can be direct buried for low volatage.
THHN vs. XHHW
The wires and circuits are also used to sense when a train is in the power sector. I ran conduit connected to waterproof boxes as close as I could but eventually that wire had to be run out of the waterproof connections to the track.
I continued to run the trains and verify the electrical connections and all worked fine. There are two parts to these supply wires. One is to provide 18v power to the track and run the locomotives. The second is provide feedback to my Digitrax BDL168s to sense if a locomotive is on a section of the track. The BDL168 does this by detecting a change in the resistance and then reports it to the command module (DCS200). I connect my Digitrax components to my computer and JMRI and then I can see on my screen when a locomotive is in a section of the track and I can also access this information from python script programs to determine what the program should do. The BDL168 can also determine the ID of the locomotive and report it back to JMRI.
We added landscape walls and then filled in with dirt to build up to the level of the tracks. I secured the wires to make sure they weren’t damaged but in most cases this put them below the top into the dirt.
Well I tested after the landscaping and found many sensor errors. The wires provided power to the locomotives fine, they ran but I would get false sensor readings around the layout. I decided to pull some wires out of the dirt. These wires ran from BDL168 through the conduit, through the waterproof box and then I brought them above the dirt, wiped off the dirt. The sensor ghost went away. Either the signal sensing is so sensitive or I have the wrong type of wire. As I checked the wire, I found in some instances the sheathing was damaged slightly from pulling through the conduit or from exiting out of one of the waterproof boxes or from where it was attached running from the boxes to the track. Either way almost every wire had to be pulled out.
I ended doing this throughout my entire layout to clean up those sensor ghosts. Now I need to figure out is there a better wire to insulate them from the dirt or a way to hide them on the layout. After research, I found there was a newer type of wire XHHW-2. Supposedly XHHW will hold up better and protect from moisture better. I will be trying this in the future.