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Tried using a cheap non-contact voltage tester on a 480V panel and got a nasty surprise
I was doing a panel swap in an old warehouse in Detroit last week and used my usual $20 NCVT to check if the feeders were dead. It beeped at me saying no voltage so I started pulling wires, but my meter showed 277V phase to ground when I double-checked. Turns out those cheap testers can get fooled by induced voltage or bad shielding on old wire. Anyone else had a fake reading from a non-contact tester on industrial gear?
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jade6183mo ago
Yeah I had this happen two summers ago on a 480V bucket truck in a Michigan auto plant. The NCVT was chirping at me saying dead but I remembered the rubber gloves story from an old timer so I threw my Fluke on it and it showed 320V. What gets me is those cheap testers are basically just a fancy antenna and on old rubber cable with high capacitance they'll pick up ghost voltage from adjacent live wires. If the feeder is running in the same conduit as something hot it'll fool the tester into thinking there's nothing there because the induced field cancels out. I always double check with a solenoid tester now even if it takes an extra five minutes.
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