Trenching for DIY solar install conduit

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JimP42

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I have a pretty good handle on the codes, county requirements, and Duke/Progress Energy requirements for a grid tied net metering solar system and a design for what I want to do.

My sticking point is about 200’ of trenching in rocky soil about 18-24” deep. Lots of rocks - I don’t know whether any are large enough to be a show-stopper, or whether major obstacles allow a variance in burial depth code. How do I go about finding someone that can do the trenching? (Chatham county) I don’t think it would be a good use of time or risk for me to rent a mini-ex and try to learn to DIY that as well. I’d like to get the trenching done and then once I know that is feasible, get all the permits, lay conduit, and do the install.

Thanks
 
Mini excavator is easy to learn and fun to drive, at least for a few hours.

Maybe look at landscape contractors if you want to outsource it.
 
Make sure you complete an application with Duke/Progress before you spend any money for something that will be grid tied. You'll need to submit drawings to them. Last time I asked the application fee was $400 for net metering IIRC.
 
FarpinDar said:
Make sure you complete an application with Duke/Progress before you spend any money for something that will be grid tied. You'll need to submit drawings to them. Last time I asked the application fee was $400 for net metering IIRC.
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I have talked to them already. There is a state agency to deal with as well.
 
A ditch witch AKA trencher is pretty simple to use and will knock out 200 feet quick.

I've done a few 50 to 100 foot runs. Keep in mind you can realistically only go backwards. Turns and curves need to be gradual.
 
Meant to add before starting make sure you know what is going on the trench.

No experience with a solar setup. Is a communication line needed?

While you got the trencher want to run a garden hose line somewhere? Light or plug somewhere?
 
falconew said:
Lowe’s you can rent a trencher.
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Will a trencher go down 2 feet and handle basketball sized rocks? The guys that buried the DSL line to my house had a trencher that was huge and it had a very hard time doing 6” for a single buried coax wire (and it was forced to the surface in a couple places by rock). It also busted a hose and dumped gallons of fluid in my yard.

I need 2” conduit down something around 18 or 24 inches. Forget which. Lowes doesn’t appear to do rental closer than 60 miles from here :-(. United Rentals does but I think I’d rather hire this part out. I don’t want to break somebody else’s trencher or mini-ex.
 
DogFather said:
Meant to add before starting make sure you know what is going on the trench.

No experience with a solar setup. Is a communication line needed?

While you got the trencher want to run a garden hose line somewhere? Light or plug somewhere?
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All I am planning to put in it a 1.5 or 2” conduit with 8 10 gauge THWN wires and a base copper 6 gauge. Wires will be carrying ~450V DC. (Normal for solar, even if it sounds extreme.) No control wires are needed for solar.

The NEC says that 1” conduit is sufficient for those wires but I suspect that pulling through 220’ of conduit will not be easy at all. Never tried though. Planning to pull it on the ground through straight pipe, then add the risers on both ends, then put in trench. I will upsize the conduit to 1.5 or 2” but even simple conduit is ridiculously expensive now.

I will probably run a direct burial cat6 cable next to conduit.

Now that I think about it probably wouldn’t hurt to run a couple of 12 ga wires as well, so that I could at least have 20A for lights and incidentals in the shop when grid is down (from batteries and inverter in house).

I thought about running water to the shop (panels will be on shop roof) and sewer back. Tempting, but probably not worth it.
 
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JimP42 said:
Will a trencher go down 2 feet and handle basketball sized rocks? The guys that buried the DSL line to my house had a trencher that was huge and it had a very hard time doing 6” for a single buried coax wire (and it was forced to the surface in a couple places by rock). It also busted a hose and dumped gallons of fluid in my yard.

I need 2” conduit down something around 18 or 24 inches. Forget which. Lowes doesn’t appear to do rental closer than 60 miles from here :-(. United Rentals does but I think I’d rather hire this part out. I don’t want to break somebody else’s trencher or mini-ex.
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The home Improvement rentals won’t do what you need to do. Most have a 24” digger but won’t actually go that deep, nor will they handle rocks or roots. I needed to bury 2” conduit here from house to outbuilding and was gonna rent a walk behind trencher. The lady at the rental place giggled when I told her what I was gonna do and told me their POS little trencher wouldn’t do it. But she rented me a kubota excavator for the same price and that did it, plus I was able to use it to clean up some other stuff and place some railroad ties with it.
 
Run aluminum mobile home feed instead of copper, direct burial no conduit needed except at each end. Transition to copper at each end.
Smaller conduit for any data or control lines.
Smaller solar panel and battery st shop for lights vs running a line for that.
Edit: you can order what you need at HD or Lowe's by the foot for two conducters.
 
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You could save some sweat by using rigid metal conduit which only needs to be buried 6" below grade provided it doesn't pass under a driveway or street. Of course its gonna cost a bunch more than PVC conduit so pick your poison. If you go that route buy material from a real electrical supply house not a big box retailer.
 
A true ride on ditch witch is not going to be happy as mentioned before for any rocks over softball size with the trencher end. If you do end up going that route besure its one that has a backhoe attachment on front to dig with in those really rocky areas when you hit one or you will be doing it by hand. But as others have mentioned the mini ex is the safer choice for dealing with ground with many rocks and more user friendly just may take a little longer to dig it but not bad. You will also have more room to work in the trench.
 
Scsmith42 said:
Personally I’d put the Cat 6 in some type of conduit. Rocks have been known to wear through the jacket over time. You don’t need 1-1/2” for it - I’d probably opt for 3/4”.
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Maybe. If I use burial cable anyway I could put it in relatively inexpensive 3/4” HDPE conduit that I can get in a 300’ roll.
 
JimP42 said:
They seem to be overkill - looks all commercial. Do you know whether they do small residential jobs?
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They definitely can do the heavy duty stuff, but we've hired them to do a simple run of buried power cable or even ethernet. I don't know if they do residential, jobs or not, and if not they may be able to recommend someone who does.

The thing is, especially with the dirt around here, digging 6" or 24", either way is going to require a piece of machinery.
 
This should work



OK maybe a little overkill, but yeah, the walk behind trenchers aren't going to like rock that big.
 
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