Help with transition from overhead to underground

[sparky1591]

I was tasked with transitioning the overhead wires between 2 electrical pole to underground. The specs call for (2) #8, 120V, 1 PH.

The original overhead wires were twisted together (is there a reason for that?). Can I just order 2 spool of #8 AWG THHN and run them underground through PVC SCH40? Or is there a specific type of wire for this situation? The work is being done in Guam.

I couldn't get to the other side to take a closer look of the overhead wire because it is fenced and belong to a military installation (we haven't get to the electrical portion just yet). All I'm doing right now is ordering all the material to get ready when we come to that part.

 

[roger]

The overhead is just a duplex service cable, the bare is the messenger. It can also be done by lashing. Yes, if you are trying to get rid of the overhead you can run PVC and THWN underground.

 

[retirede]

The existing overhead wires consist of an insulated conductor and a bare neutral which also serves as the messenger and has a steel wire in its center (ACSR). They are twisted so that the messenger also carries the weight of the insulated conductor.

If the poles are in an area considered subject to physical damage, the PVC should transition to schedule 80 where it comes out of the ground.

 

[sparky1591]

The overhead is just a duplex service cable, the bare is the messenger. It can also be done by lashing. Yes, if you are trying to get rid of the overhead you can run PVC and THWN underground.

So when I order one, I can just order two normal spool of THWN #8 AWG both insulated?

 

[roger]

So when I order one, I can just order two normal spool of THWN #8 AWG both insulated?

One will have to be a color other than white, gray, or green and the other can be white or gray

 

[don_resqcapt19]

So when I order one, I can just order two normal spool of THWN #8 AWG both insulated?

You need an EGC.

 

[CoolWill]

You need an EGC.

But I. This case, the overhead drop is just a bare neutral and a hot, so does he add an EGC tied to the bare neutral just to run it in pipe?

 

[retirede]

But I. This case, the overhead drop is just a bare neutral and a hot, so does he add an EGC tied to the bare neutral just to run it in pipe?

If he’s not tasked with running the circuit back to its source, there is no EGC. And the proverbial can of worms has been opened!

 

[don_resqcapt19]

I see no provision in the code that would permit this installation without adding an EGC from the power source.

 

[sparky1591]

I see no provision in the code that would permit this installation without adding an EGC from the power source.

I see no ground conductor being run with the overhead duplex, and the print only specific (2) #8, there 10 poles total and we have to take down 2 poles in the middle to make way for an access road; that's why we need to reroute the overhead to underground.

 

[don_resqcapt19]

I see no ground conductor being run with the overhead duplex, and the print only specific (2) #8, there 10 poles total and we have to take down 2 poles in the middle to make way for an access road; that's why we need to reroute the overhead to underground.

Assuming the installation is covered by the NEC, there is no provision that permits this work without installing an EGC from the source. If I am inspecting this, you would have to bring the whole circuit up to code.