I have seen up to 90 volts of 'phantom' voltage with my Fluke 87 on open conductors that share a raceway with other 277 circuits.
It is never just millivolts, the meter left unconnected shows millivolt readings.
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I agree with the above posters that for general line volt troubleshooting leave the DMM in the truck and use any solenoid type tester. They don't lie, assuming you check them against a known live circuit.
Bob
