Greg1707
Senior Member
- Location
- Alexandria, VA
- Occupation
- Business owner Electrical contractor
Note: URD is not an approved NEC wiring method but your picture indicates at least one of the conductors is USE-2 which is approved for direct burial and for use in a conduit.
That is a common cabling and marking for the triplex he has pictured. The THWN is the oddball.
Since the EGC can (in most cases) be bare copper and still be direct buried, I have no issue with using copper THWN for the EGC here.
Around here, SH's did not stock 4/wire until 15-20 years ago (because "nobody bought it", self-fulfilling statement), so I have seen and done similar installations4 wire mobile home feeder may have been a simpler choice for this installation, but I don't know the circumstances.