Hi y'all,

Help me out here--I'm missing something and just can't see to clear.

I was working in an area used now for retail, previously was a cannery (built in the late '40s). Supplied with 480/277 with stepdown transformers where 240/120 is needed.

Tenant wanted a few 120V receptacles in the center of the space. On a support column, I found a blanked-off single gang handy box at the end of a run of heavywall. Opened it up, see two wires, rag and tar insulation, one w/white paint.

Using a solenoid voltage tester (Knopp), I find 120V from white wire to conduit ground (not unusual in this facility, a lot of the identified conductors are hot--so much for "qualified" maintenance men), and 120V between the two conductors. So far so good. Then I check from black to ground and get 240V.

My first thought is that the conduit is at 120V to ground. I check with a Greelee
volt-tic, find no voltage. Then I check with a CTC/Fluke 9970 voltage detector (used by telco linemen to make sure they don't have forgien voltage on terminal boxes). No voltage.

I re-capped the conductors and reinstalled the blank plate. I can't figure out why the 240V to ground. It's not phantom voltage. What am I missing?

I am going to be back at the facility late this week for some phone and data wiring. Any additional (quick and easy) test I could do to pin this down? I was thinking of running a lead to a known good ground and testing the conduit-to-ground voltage with the Knopp.

Any suggestions appreciated.

Cliff