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Putting different components in underground ditch.

3K views 11 replies 7 participants last post by  Roy Rowlett 
#1 ·
I am running wire to a workshop for a 60 amp sub-panel. I am thinking I will use 6-3 THWN in conduit. I also need to run coaxial cable, smalll gauge control wires, water, and cat-5 phone wire. Is there any reason that I cannot put all this in the same ditch? Should I put the 6-3 in the bottom of the ditch for added protection, or should I be concerned about running a water line above the 6-3 in the dutch? I plan to bury at least 18" below grade.
 
#2 ·
Low voltage and high voltage should not touch, the further apart the better. AC will cause interference with low voltage gadgets. Water/gas/etc., should be by themselves. Not sure where you are, but 18" is not deep enough here, for water, it would freeze. But it is common for all those things to be in one trench, just separated.
 
#7 ·
Essentially none. By code, you cannot run the low voltage wires in the same conduit as the power (well, you probably can't, depending on some things) but no real separation is necessary. Coax will not receive any interference because of the type of signal used - it is modulated RF, and not subject to 60Hz interference at all. Phone will not receive much if any interference because the wires are bundled together and twisted, so all wires in the phone cable receive the same interference and it cancels out. Your other control wires will be fine too, assuming they are operating relays or something similar and are not digital signal lines.
 
#5 ·
I've run 480 volt power, phone, data, security camera, instrumentation, etc., in the same ditch with minimal separation without problems.

Just about any low-voltage device these days is immune to 60 HZ interference. Older stuff had trouble occasionally, but not anything built in the last 20 years.

Rob
 
#6 ·
One clue about interference is to see the separation on the overhead lines. At the roof mast, the coax and power have less than 12" separation, and that is a 50' run. I think the separation requirement is more from safety/possible shorting than interference.
 
#8 ·
Not 6-3 unless you are excluding the ground. You need 4 wires to your sub-panel (H-H-N-Grd) The sub-panel needs to have neutral and ground isolated electrically...no bonding of the two. So what you need is 3 #6's two black (hots) and one white (neutral) and 1 #10 ground. This is for a 60 amp feeder. The top of the conduit to grade needs to be 18" so over trench the depth a tad. If your in an area that has a freeze depth and your going to be above that with water then if possible put in a valve box that allows you to drain the pipe. I agree with ROB on interference but you probably will have a local code that requires 12" seperation of water and electrical and they usually want water at the bottom of the trench. so check locally cause you may have to trench deeper than you expect to meet minimum local code.

Any pvc above ground will likely need to be sch. 80 due to physical protection requirements. You can if you want run a cable 6/3 grd then splice in jb to your thwn to go underground. I hate splices though on feeders like yours but is fine if you want.


You will also need a main disconnect at the garage....main breaker panel is usually the easiest way to meet that requirements. Personally I like a rremote main disconnect located outside or immediately inside at the point of entrance of the feeder then feeding a mlo panel from there.

Your sub-feeder will follow these guide lines........
 

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#9 ·
The conduit alone will give all the separation required. Choose the size conduit you think you will need and double it for each run. Conduit is cheap. Having to dig it up again is not. Pull a string in each one too. In case you want to run something else out there. This is your chance to do it right, the first time.
You need 4 wires in that 60 amp feeder not three. H-H-N-G.
 
#10 ·
I meant to say 6-3 with gnd, but failed to include that. I plan to drive a separate ground rod outside the shop also and add that to the ground bar in the sub-panel where the ground wire from the main house panel is connected. This should tie both grounds together and make sure they are all at the same potential.
 
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