- Q. I'm a remodeler and often work around existing wiring. What's the most practical and inexpensive tool for detecting live current in either romex or wire in a metal conduit? Can you detect current inside the conduit without opening the conduit?
A.Rex Cauldwell responds: In my opinion, the only dependable way to detect live current — the way I would want to bet my life on — is with a multimeter connected to the wires. Check the voltage, conduit to ground, ground to hot, ground to neutral, and neutral to hot.
The wands, or "sniffers," I've used — the types you wave over the wires to tell you whether they're hot — have not been dependable. I have had many that gave false readings.
Regarding wires in conduit, you must remember that the conduit may be grounded, which would give a "dead" reading when the wires inside are hot. Another problem with low-cost voltage sensor pens is that many don't detect voltages of less than 60 volts. Thus, if there is a low-voltage circuit or a circuit making intermittent contact, the sensor won't pick it up.
One unit that I have not tried but that looks promising is made by Extech Instruments of Waltham, Mass. (781/890-7440, www.extech.com). Their model DVA30 ($39 on the web) is claimed to measure from 5 to 250 VAC through conduit or shielded wire.
Rex Cauldwell is a master electrician in Roanoke, Va., a frequent contributor to JLC, and the author of several books, including Wiring a House.
