Klein Tools RT390 Circuit Analyzer with Large LCD, Identifies Wiring Faults, GFCI and AFCI Tester, Voltage Drop, Displays Trip Time

I got the Klein RT390 mainly to look at voltage drop; I have one GFCI outlet and no GFCI or AFCI breakers. Given that, I probably didn’t stress the analyzer as much as some of the other reviewers did. I’m also not a practicing electrician, so I haven’t given the unit heavy use. My rating is based on using it for only a day, and it’s something I probably won’t be repeating on a daily basis. So I cannot really comment on reliability.The RT390 greatly simplifies measuring voltage drop by giving results at three different loads—12 A, 15 A, and 20 A—with the press of a button. The results are displayed for five minutes, even if the cable is disconnected, so it’s easy to take the analyzer to a computer to record the results; I put them into a spreadsheet that does some additional calculations, like estimating the length of the circuit under test.The detachable cable is handy. The one supplied can be a bit short for some applications; I got a 2′ 14 AWG cable for some harder-to-reach locations; you probably could go a bit longer without serious problems. I also got a NEMA 5-15P to IEC C13 adapter (https://www.amazon.com/dp/B0CT7HB42J) for direct plug in.It’s nice that Klein provide a case, but unlike most Fluke cases, the case isn’t padded and isn’t very protective—I would not want to drop it. The RT390 costs as much as many multimeters, so it’s worth protecting. To address this, I got a Jinmei EVA hard case (https://www.amazon.com/dp/B0C24N9Z5W).Testing Ungrounded DevicesAs has been noted by some others, the analyzer will not perform any tests with “incorrect” wiring, so out of the box, it cannot be used on ungrounded receptacles or lamp sockets. But it’s simple to work around this if a good ground is available. I have a grounding wire that plugs into a grounded receptacle. I’ve used it to properly ground an antistatic mat; many of the better antistatic mats include such an adapter. I made mine from an old extension cord, but it could easily be made with green wire and a plug. I only extended the grounding conductor. I retained the neutral blade on the plug to keep the plug from spinning in the receptacle; I cut off the line blade and taped over it to minimize any chance of something unpleasant happening. If you make an adapter from scratch, connect only a green wire, and there should be no problemFinding the Source of a Voltage DropAs supplied, the RT390 is mainly aimed at testing receptacles. But what to do if the load test shows an unacceptable voltage drop? The logical approach is to test points closer and closer to the supply to try to see where the problem starts. On some circuits, the available test points nearest the supply may be light fixtures or switches—so plugging into a receptacle won’t address the problem.Testing a Light FixtureThe analyzer cable is inserted into a 3-wire to 2-wire plug adapter inserted into a socket adapter, and the grounding wire is connected to the grounding tab on the plug adapter. It’s a bit trickier if there aren’t any grounded receptacles handy, but a grounding wire can be connected to some other reasonable ground is available. I didn’t need to do this, so I can’t comment on what constitutes a “reasonable” ground.Do be aware that while a socket adapter (https://www.amazon.com/dp/B0CDRFPD9G) accepts a 3-wire plug, it does not provide a protective ground because there is no ground in the socket to which it can connect.A Problem I’d Never Have Thought to InvestigateDoing a test on a light fixture above a kitchen sink was revelatory. With my grounding hack connected, the RT390 happily … refused to do the test because the line and neutral were reversed. A check with a DMM confirmed that the socket threads were energized—and apparently have been for 70 years (I guess this stuff wasn’t taken too seriously in the era of 2-wire nonpolarized plugs). Arguably not the world’s worst safety hazard, but if one were to screw in a bulb with the socket energized and manage to touch the threads, it might not be fun. Especially if water had been splashed on the floor. After the fixture was correctly wired, the analyzer was glad to complete the test. Had the analyzer not been so fussy, I’d never have thought to test the fixture for correct wiring.Testing a Switch or Other Connection PointConnection to switch terminals requires some improvised wiring. Some manufacturers—such as Ideal—offer an IEC C13 to alligator clip adapter (https://www.amazon.com/dp/B000R99RFI); here again, the RT390’s detachable cord is mighty handy. When connecting something like this to a switch or to light-fixture wiring, it’s imperative to take the utmost care to avoid a short circuit or even connections so close as to allow arcing. Watching a Fluke video on arc faults should convince that great care is indicated when making such connections.It’s possible to make an alligator-clip adapter; an internet search should find some examples. If doing so, you should be very careful, especially with alligator clips that aren’t fully insulated like those on the Ideal SureTest® adapter. It′s something I’m not willing to risk.A Low-Cost AlternativeYou can do a surprisingly good job with an inexpensive power meter (such as a Kill A Watt; I have the P4400) and something like a hair dryer, but it can be a bit tedious, and there’s limited choice of loads. Unlike a Kill A Watt, though, the RT390 doesn’t show the actual current; I’m not sure the nominal loads are adjusted for voltage drop. I’m not sure it really matters, though. Results with the RT390 track pretty closely with those with the Kill A Watt and hair dryer.ConclusionThere are other testers—like the Extech CT270 (https://www.amazon.com/dp/B0058ELNFY)—that provide more information for a lot more money. And there are others that cost far more than that; some—like models from Ideal and Amprobe—appear to have been discontinued. For someone who’s not an electrician, even the RT390 is arguably massive overkill. Many simple testers will check for correct receptacle wiring; every home should have one. But it is nice to know if you have excessive voltage drop, especially in an older building. And especially if you strongly suspect that you have some marginal wiring. The RT390 makes that testing a breeze.

Great tool. Does exactly what it is supposed to. High quality and a fair price.

Works great, just what I need for troubleshooting

I found this outlet tester to be incredibly reliable, providing me with a sense of security when working on minor household projects. Its user-friendly design made it a breeze to use, and I particularly appreciated the sleek blue color it came in. This tool not only made testing outlets a simple task but also gave me peace of mind knowing that I was working in a safe environment. I highly recommend this outlet tester to anyone looking to ensure the safety of their electrical systems at home.

This meter performs the same functions as meters costing twice as much.

Loved the feature shows voltage drop and help a lot to diagnose a faulty circuit

works good

Bought this to do load testing on old non grounded outlets. Won’t work by itself. I made a male to make ground plug(see picture). Just need a grounded outlet somewhere, use extension cord and plug into bottom side of same outlet. Worked fine, can also use this setup to test gfci and afci. The adapter should only extend the ground lead so as NOT to be a suicide cord. Test the grounded outlet first to verify its wire correctly ( not hot ground reverse ). This is just a temporary setup to supply the ground that the tester is looking for BEFORE running its test. I am not an electrician. If uncertain or not familiar with electricity leave it alone.