A non-contact voltage tester is a useful tool for any kind of electrical work—there’s no quicker or simpler way to safely check for electrical current in a wire, outlet, switch, or an old lamp that has mysteriously stopped working. Every electrician carries one. And after talking to a 20-year veteran electrician and performing eight months of testing with seven leading models, we found that the Klein NCVT-3 (about $25) is the best one to get.
This is a dual-voltage model, so it registers both standard voltage (house wiring) and low voltage (like irrigation, doorbells, thermostats). And unlike some models we tested, it can automatically tell the difference. This feature also makes it compatible with tamper-resistant outlets, which are now required by electrical code. The controls on the NCVT-3 are intuitive, the display is clear, and when testing it in a breaker panel full of live and dead wires, it was sensitive enough to read a dead wire from a short distance without giving us false positives from nearby live wires. But the most useful feature is actually its bright LED flashlight, which, unlike every other tool we tested, can be operated independently of the voltage tester. For a tool that’s often used in dim basements—or situations where the lights aren’t working—this is a minor but very helpful feature. According to Klein, the tool can handle a drop of up to 6½ feet, which isn’t bad considering it’s a delicate piece of electronics.
If you can’t find the Klein, we also like the Milwaukee 2203-20 Voltage Detector with LED (about $25). It’s similar to the Klein where it counts—it detects standard and low voltage and is simple to use—but the flashlight isn’t as bright and can’t be used independently of the tester. It’s also makes an incredibly loud beep, with no mute option.
I’ve been writing about and reviewing tools since 2007, with articles appearing in Fine Homebuilding, This Old House, Popular Science, Popular Mechanics, and Tools of the Trade, where I’m a contributing editor. I’ve also spent 10 years in the trades as a carpenter, foreman, and job site supervisor working on multimillion-dollar residential projects. I also recently gutted my 100-year-old farmhouse, which required a whole new electrical system.
For more information on non-contact voltage testers, I spoke with someone who uses them every day: Mark Tierney of Tierney Electrical out of Hopkinton, Massachusetts. Tierney has 20 years of experience and has run his own company since 2010.
A non-contact voltage tester detects electricity in a wire or outlet, just by getting near it.1 It is the size and shape of a fat Sharpie and the detection occurs at the probe tip, which, in many cases, is designed to be pushed into an outlet. Because electrical shocks are unpleasant at best and extremely harmful at worst, this tool is useful for even the lightest electrical work, like troubleshooting a thermostat or installing a dimmer switch.
Obviously, it’s a good tool for the DIY electrician, but even someone with zero electrical inclination can benefit from owning one. I commonly use one as the first stage of troubleshooting before calling a professional electrician. In one house I lived in, I had a poorly labeled breaker box, so I used the tool to map out my system, allowing me to know which breakers controlled which rooms.
Most non-contact testers register only standard voltage. After reading what we could on the subject, we decided that a dual-range voltage tester would be better for the home toolbox. It still works the same for standard voltage, and there is the added benefit of low-voltage detection, which is useful for doorbells, thermostats, some AV equipment, irrigation, and some landscape lighting. All of the models (dual and single voltage) fall primarily in the $15 to $25 range, so a dual-range unit makes sense as a one-stop tool for the non-specialist. Basically, it’s better to have the capability and not use it, than to need it and not have it.
In deciding which models to test, we researched units at Amazon, Home Depot, and Lowes. We also keyed in on reputable manufacturers of electrical tools. From that, we narrowed our list down to seven.
We ran a few tests to determine the overall usefulness and sensitivity of each tester. First, I shut off a single breaker at my electrical box and tried to discover which of the 35 wires coming out of it was the dead one. After that, I took a dead wire and saw how close I could get the tool to a live wire and still have the tester read negative. In addition to those structured tests, I used the testers as I wired some outlets, and installed some dimmer switches, a cooktop, a ceiling fan, and a few pendant lights.
After researching the topic, talking to an electrician, and spending hours testing seven leading models, we recommend the Klein NCVT-3. The NCVT-3 has a very intuitive indicator light, a nice on/off button, and an onboard LED that works like a little flashlight. This is a great feature, seeing as the lights may not be working too well when you’re checking wires for voltage. It is also compatible with tamper-resistant outlets, now required by code. The NCVT-3 has a battery life indicator and a durable body that protects its sensitive electronics from a fall of up to 6½ feet.
Most of all, the NCVT-3 is very easy to use. It’s a dual-range unit, so it can detect standard voltage (outlets, regular wiring) as well as low voltage (doorbells, thermostats, irrigation wiring). Most testers detect only standard voltage. Unlike most other dual-range models, it switches between the ranges automatically without the use of a fussy sensitivity dial. An LED bar graph at the side of the tool indicates which voltage you’re dealing with. A low voltage detection lights up the lower two orange lights and standard voltage lights up one or more of the upper three red lights. Many companies sell separate high- and low-voltage detectors, but for the non-specialist, it makes sense to have them in a single tool, particularly if it works as easily as the Klein.
The LED flashlight is a high point of the NCVT-3. In my own basement, the wires are stapled to the ceiling above the fluorescent lights, so even with the lights on, it’s hard to work with the wires. Of the two models with an onboard flashlight, the NCVT-3’s is the only one that can be operated independently from the testing function, which is really nice. When the tester is activated, a series of beeps and blinking lights occur and it’s nice to be able to sidestep that if you’re just trying to use the flashlight. Our runner-up selection, the Milwaukee 2203-20 Voltage Detector with LED also has a flashlight function, but it comes on only when the tester is activated, so no matter what, you have to listen to the beeps and there is no way to shut the flashlight off, even if you’re working in a well-lit room. The NCVT-3 LED is also brighter than the Milwaukee.
The NCVT-3 also has a very durable feel to it. According to the manufacturer, it can withstand a fall of 6½ feet, so if you get a case of the dropsies, this model will give you a shot at survival. In addition, the buttons are all sealed and the cap of the battery compartment is gasketed, so the NCVT-3 can handle a little rain and dampness. Klein has a video of the tool where it looks like it’s under a steadily dripping faucet.
When we asked electrician Mark Tierney if there were any manufacturers he would recommend to a homeowner, he told us that the “the one that has been the most reliable is the Klein.” He also likes the models that come with the LEDs saying that for a homeowner, “they would get two great features in one tool.”
For battery life, Klein says that the two AAA batteries will provide 15 hours of continuous tester use and six hours of continuous flashlight use. This is plenty for the occasional user, and like we said, it’s nice that there is a battery indicator light, so that you’ll know when it is getting low.
And we’re not the only ones that like the NCVT-3. Clint DeBoer, writing at ProToolReviews, says that the tool “is as close to a no-brainer as you can get if you even occasionally do electrical work.” He concludes his review with, “This is a well-designed tool that does what it’s supposed to and does it well. Pick one up. You won’t regret it.”
Even though the NCVT-3 has been released for only a few months, the feedback on it is positive overall. At Home Depot, it has a rating of 4.4 stars with seven reviews, and at Amazon it comes in a little lower at 3.5 with six reviews. Most of the negatives at Amazon are from people who like the tool but are disappointed that it cannot be inserted into an outlet. As we described above, this is not an issue because it can still detect the current, only displaying it as low voltage (and making it compatible with code-required tamper-resistant outlets). To truly confirm standard voltage on an outlet, it’s easy enough to unscrew the cover plate and place the tip of the tool at the side of the outlet where the wires are.
The NCVT-3 is unique because it cannot be inserted into an outlet. At first glance, this seems like a problem, seeing as most other non-contact testers read power from an outlet only by being inserted into one of the openings. The reality is that because it can read low voltage, the NCVT-3 can still pick up the current from the outside of the outlet, which is essential when dealing with tamper-resistant outlets, now required by electrical code. To insert a plug in one of these outlets requires equal pressure on both prong openings (it’s a safety issue for children). With these outlets, a traditional non-contact voltage tester doesn’t always work because it can read only standard voltage. As Bruce Kuhn, Klein’s director of product development, test and measurements products, told us, “If you make a tester like this sensitive enough to detect voltage on the ‘outside’ of a tamper-resistant outlet, it will be too sensitive in a crowded electrical box that contains several hot wires.”2 Because the NCVT-3 is designed to detect standard and low voltage, when it is placed at the openings of a live tamper-resistant outlet, it picks up the standard voltage, but from a distance, displaying it as low voltage, still confirming that the outlet is live.
The NCVT-3 has the control buttons on the side, which is something Tierney told us to watch for. He warned that models with a side button easily turn on when they’re in a pocket, which is not only annoying, but also speeds up battery drain. One redeeming difference with the NCVT-3 is that the buttons are flush with the surface; most buttons like this stick out from the side of the tool and it’s easy for them to accidentally be activated. I spent a day with the NCVT-3 in my pocket, and it didn’t turn on once.
The NCVT-3 also has no mute option, but it’s quieter than other testers we looked at.
If the Klein is not available, we recommend the Milwaukee 2203-20 Voltage Detector with LED. It has many of the same features as the Klein NCVT-3, but the flashlight isn’t as bright and can’t be used independently of the tester. It also makes an incredibly loud beep (no mute option). This could be beneficial on a noisy job site, but after I spent 45 minutes checking wires in my basement, the volume was enough to drive me a little nutty.
Still, the Milwaukee can detect the low and standard voltage, and there is no manual toggle between them, so it’s as simple to use as the NCVT-3.
We tested the Klein NCVT-2 ($20), which is very similar to the NCVT-3 except that it doesn’t have the LED; the on/off button is proud of the case (so it is likely to turn on in a pocket); and the case doesn’t have as durable a feel. It is also a dual-range model that automatically detects between the two ranges.
The Greenlee GT-16 ($22) and Sperry VD6505 ($15), which we also looked at, use a dial to select the sensitivity between low and standard voltage. During our testing, we found that when there were multiple wires in the area, those models would pick up the signal from other wires, making it difficult to know when we had the sensitivity dialed down to detect only the wire we wanted. It was tough to get the hang of the sensitivity dial and much preferred the simpler interface of the Milwaukee and Kleins.
The Greenlee TR-12A ($24) has a two-prong design, made specifically for use with tamper-resistant outlets, but it reads only standard voltage and not low voltage, so we feel the NCVT-3 is more useful.
The Klein NCVT-1 ($17) detects only standard voltage. I’ve owned one for years and have always found it to be accurate and reliable, but it makes sense to get a model that can detect low voltage as well.
Fluke, a very popular and highly regarded manufacturer of electrical equipment, does not make a dual-range unit.
Tip: If you have an old house or apartment, there is a strong chance that your electrical panel is mislabeled (I have yet to live in a house that has had anything close to a properly labeled panel). It’s time-consuming to sort it out, but a non-contact voltage tester can speed up the job. Shut down all of the breakers but one, then go around the house checking to see what’s live. Once you figure that out, label the breaker, and move on to the next one.
(Photos by Doug Mahoney)
Originally published: August 19, 2015