As described in my other question about this barn's flooring, there's an electric feeder supplying an out-of-service subpanel and circuits in a barn that is hardly enclosed anymore. I want to know if I can keep using this feeder cable, with all new subpanels and circuits in the barn.
The feeder cable is marked "10-3 WITH GROUND TYPE UF 600V SUNLIGHT RESISTANT E25682F (UL)". That starts at the main panel, connected to a standard 2-pole 30A breaker. It runs at least 170ft from the main panel to the subpanel, leaving the main basement through a hole in the cinderblock wall >2ft below grade. This electric cable emerges out of the soil in a room of the barn.
As for functionality: I tested the cable by turning the breakers on at the main panel, while the subpanel was turned off. The wires from this cable behaved as I'd expect an in-tact cable to, albeit with rust to scrape off terminals on the subpanel: both hots read apx. 120V compared with the neutral and ground, hots read 240V compared with each other, neutral and ground read 0.04V compared with each other, and all voltage readings were stable (did not flicker or change between readings once I got good contact). That seems promising.
As for code: I am in PA, USA. It looks like it is compliant with the code to use UF cable buried 2ft or more, and it is allowable to put UF cable in a conduit of sufficient size.
I would like to keep using this cable, with a few improvements:
Replace the 30A 2-pole breaker with a GFCI version for added safety
Detach this cable from the existing subpanel, tape it off, then slide metal conduit over the cable so that within the barn it is safe from abrasion. (I plan to use this room as a small workshop.)
Replace the subpanel with something and all circuits in the barn. I understand this 10/3 UF cable is sufficient for each wire to carry 30A loads maximum, meaning the barn subpanel can have a maximum of 30A 120V or 240V power supply. I expect to have just (3) 20A 120V circuits: lights, tool outlets used one at a time, and electronics outlets that would at most power a small electric space heater.
Does that sound reasonable? Are there other improvements I should make or ways I should test this, particularly its grounding capabilities, to ensure it is safe for continued use?
Here is the cable leaving the basement, just 5-10ft from the main panel. The hole in the cinderblocks has a piece of PVC with which a heavy duty water hose runs through (not connected to anything on either side for now). The white cable runs to the barn's subpanel, exiting the house's basement along the outside of that PVC piece. There's a black cable in this photo that does not go to the barn.