When you have to trench 50 or 60'or maybe 150'? We normally get a trencher from Home Depot and trench 18" down. The way I read the NEC, since we are over 30V with POE, we need to be 18" if in conduit.
But sometimes we hit rocks, have to go through areas with tree roots, etc and it becomes an absolute nightmare.
[IPVM Note: Cable Trenching for Surveillance]
I'm not sure PoE use crosses over into high voltage requirements per NEC. In my area, trenching depth is influence by water table height and frostline in other areas, but I have not had an AHJ express minimum depth because of dangerous voltage.
In my area, trenching depth is often 12". But it isn't uncommon to find cable nearly exposed and basically laying on the surface. Just the 'kick some dirt over it' method... yikes!
Table 300.5 in the 2011 NEC calls for depths up to 24" depending on the installation and conduit used. This is for 0-600V. PoE is typically 48 V with some devices using 24V, 18V, 50+? I do not see any exception for network cable?
830.47 covers Network Powered Broadband Communications systems and has specific depth requirements as well.
Either way, if not covered in concrete or driveway, it usually needs to go down 12" to 24"
Can anyone cite where POE cables are exempt?
Granted, I doubt anyone is at any risk over a POE cable.
But we use this to justify our trenching expense. We tell customers we have to bury so deep so that we are not asked to kick a little dirt over it. I have seen many failures due to this. One company I know buried a line 3 times because it kept getting cut. And it still got cut cut.
How much does it cost to trench and run conduit? Ball park?
depends on the length and obstacles. Rocks, tree roots? I usually estimate how long it will take, use my hourly labor rate and add a couple hours to cover the trencher rental, time at rental store, tool cleanup etc.
We do a bit of trenching and I hate when a job requires it, because it is a place where we will not shortcut, and many others will. So it makes it our quote seem much higher.
I leave it to the experts. We sub it out to electrical contractors we work with a lot. They will bore or trench (depending on the location). They have the equipment and knowledge to deal with (or find) existing cables, roots, rocks, etc. They will also know the code requirements and possible permits required. Too much liability for us to try "renting something" and giving it a go.
As for price - have a recent bid of $1,920 to bore under a parking lot about 100' from main building to a remote building. includes conduit in ground and connections to the building (and pull string).
Had another one where they trenched about 500' down the side of the road on the campus to pole where we installed a camera and a light. They also had company come out and take readings for the path to find anything existing buried. Had two conduits (fiber for one and 240vac for the light in the other) that was $4,300 (trenching, fill, seed straw, conduits, building connection and pull strings)
Ask questions and get answers to your physical security questions from IPVM team members and fellow subscribers.
