Underground Boring

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bwat

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Underground bore (not a trench) for 15kV MV feeder. It needs to make multiple turns along route. I assume I need something like a sectionalizer cabinet at the end of each straight section, in addition to bore pits.

Is that correct? Are there any other options? Perhaps I need only the bore pits but not necessarily the sectionalizer cabinets?

Can't really just slap in a JB so easily with MV circuits. Kicked around more of a large hand hole or vault as well, but wasn't sure about that.

Likely looking at #2 MV-105 for cabling if that's helpful.



Appreciate any recommendations and input!
 
Not sure why you would need a sectionalizer cabinet. Just need a manhole to be used as a pull point.
Note that if there is room in the right away that you are boring in, the directional bore can make turns.

If you use a manhole make sure that you can get a "U" bend of cable through the manhole cover without having to bend the cable tighter than the minimum bending radius.
 
electrofelon said:
Why not?
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I haven't seen this. Having a hard time envisioning a couple terminal blocks/polaris/split-bolt equivalent in a simple box for 15kV feed. Have you done something similar before or are you just saying anything is possible?
 
bwat said:
I haven't seen this. Having a hard time envisioning a couple terminal blocks/polaris/split-bolt equivalent in a simple box for 15kV feed. Have you done something similar before or are you just saying anything is possible?
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I would try to avoid a splice. Obviously at some point it would be worth splicing rather than pulling out a zillion feet of cable then refeeding it back in. I don't know the specifics of your installation. Splicing the MV cable should not be that big a deal. You could also use something like a pad mount switch using load break connectors if you wanted above ground access.
 
Directional boring can make turns but has turning radius limitations and possibly even number of turns limitations to some extent and I could see soil conditions contributing to what you can or can't do as well.

If you need to make a rather short radius turn you don't necessarily need a box or man hole, but do need to excavate a hole at the turn point and would be feeding cable in one direction while pulling from another direction just like if you had a pull box in a raceway run. This assumes you can pull the cable through the bored hole easily enough to do so, if not might want to pull raceway through the bored hole then pull cable through that, or pull raceway both ways and install an elbow in the hole where the turn is made then pull through the entire run afterwards.

Directional boring doesn't mean there will be no excavation at all, just has limited excavation compared to conventional methods of installation.
 
The typical bend radius is under 150 feet and you only need to have pits at the entry and exit. The bend radius will increase as the pipe size increases but not by much unless you are pulling back really large poly. I don't know what the requirements are for the OP, I just wasn't sure if he understood how controllable directional boring was.
 
bwat said:
I haven't seen this. Having a hard time envisioning a couple terminal blocks/polaris/split-bolt equivalent in a simple box for 15kV feed. Have you done something similar before or are you just saying anything is possible?
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I watched some electricians splice some 15 kv cable together once. It took longer than low voltage stuff but was not overly complex nor did it take up a huge amount of volume to do so. It was made up inside a MV mcc but I would bet the splices could have fit in a 24x24x12 box. Probably not big enough to meet code requirements but the splices just did not take up that much room.

By the way, the splices were installed because the electricians that pulled the underground cable to the outdoor mcc ended up being about 3 feet short.
 
One of the buildings I work at in Seattle has a SCL hand hole with (3) 1/0 25KV CN cables. I discovered it when I was looking around for something else. No splices, must have just been a pull point. Maybe I am misremembering the size, but I don't think it was much more than a 12x24. No lock or even security bolt. SCL uses uncovered CN, luckily The scrappers didn't find it and cut the concentric neutrals off 😂
 
Thank you all. This was very helpful, as expected!

I didn't realize some of the turning capabilities with boring. I knew there were some, but thought it was more for minor offsets and avoiding small obstructions.
 
petersonra said:
I watched some electricians splice some 15 kv cable together once. It took longer than low voltage stuff but was not overly complex nor did it take up a huge amount of volume to do so. It was made up inside a MV mcc but I would bet the splices could have fit in a 24x24x12 box. Probably not big enough to meet code requirements but the splices just did not take up that much room.

By the way, the splices were installed because the electricians that pulled the underground cable to the outdoor mcc ended up being about 3 feet short.
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Depending on length of run, some cases I bet you just re-pull those cables and make sure they are long enough the second time.
 
petersonra said:
I watched some electricians splice some 15 kv cable together once. It took longer than low voltage stuff but was not overly complex nor did it take up a huge amount of volume to do so. It was made up inside a MV mcc but I would bet the splices could have fit in a 24x24x12 box. Probably not big enough to meet code requirements but the splices just did not take up that much room.

By the way, the splices were installed because the electricians that pulled the underground cable to the outdoor mcc ended up being about 3 feet short.
Click to expand...
One brand of cold shrink for a 2 AWG, 15kV conductor shows an installed length of 29" for an inline splice.
 
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