Fluke has a new outlet tester, ST120+, and it’s priced at a reasonable $20.
The Fluke ST120+ tester is an electrical troubleshooting tool that can detect common receptacle wiring issues, such as when there’s an open ground, or the hot and neutral are reversed.
It also has a GFCI test function.
As with other receptacle testers, the Fluke ST120+ has a 3 LED indicator lights, and a code legend printed on the front.
There’s one more feature – a toggleable audible alert that beeps when power is detected. Fluke says the tester will still beep when plugged into a miswired outlet. This should come in handy for identifying which circuit breaker shuts power to the outlet.
Note: This does NOT have non-contact voltage detection.
Lowe’s started carrying the Fluke tester last year, but it only recently appeared at other retailers. Lowe’s website still shows an “exclusive” label above its price, which explains why we haven’t seen it anywhere else until now.
$20 seems reasonable for what you get, especially given Fluke’s excellent reputation. The ST120+ is larger than most other outlet and GFCI testers I have seen and used, but still compact.
Shown here is an older Klein outlet tester, with the plug at one end and indicator lights at the other. This is a standard design and represents what most receptacle testers look like, although some will be missing the GFCI test button.
The Fluke design, with the plug at the back and lights on the front face, is new to me, but I don’t see why it wouldn’t work just as well. It also has a gentle curve behind the lights, which could help with readability from above.
If you want to spend less, there’s also the ST120, which has all of the same features except for the beeping function. The ST120 is priced at $15.
If you want to spend even less, you can find a Gardner Bender outlet tester with GFCI trigger function for under $10 at Amazon.
The concept for this is great and normally Fluke hit a home run but this has two flaws that annoy me enough to regret buying it.
Firstly, the form factor takes up two outlets so if you are testing circuits with something that needs to remain plugged in you have to remove whatever else is plugged in first. That’s the main reason I don’t use mine much.
Secondly, the alarm is too quiet and you definitely won’t hear it outside at the panel, or if the breakers are a few rooms away or doors are closed. It also has an annoying high frequency that makes you want to turn it off. Oh and third, its form factor prevents it fitting into a shallow tool cabinet drawer where all my testers sit so it invariably ends up getting misplaced.
The Klein you pictured (model #RT600) is my favorite GFCI tester but sadly they don’t make it any more.
I have this Klein tester and the pigtail makes it very convenient, although it’s double the price.
Question for you Dave.
I very much like the pigtail, looks to be very convenient. But like you said, twice the price for the pigtail.
I never thought about it, but I could easily make a short pigtail which I could use with any of these testers when needed.
Does this model (RT310?) have any other additional function or are you paying strictly for the pigtail?
I’m no electrician – but the RT310 advertises itself as both a AFCI and GFCI tester
Its the AFCI that makes it special. Testing GFCI is easy, draw a load between hot and ground, an LED or resistor on a switch can test this. Testing AFCI requires some work to test. I’m not sure what method this uses to simulate an Arc Fault. I assume there is a timing circuit as high inrush current would be bad if the AFCI was faulty.
So, you plug this in and if there is an arc fault detected, it will let you know.
A bad arc fault which is almost constant, it will detect. What about an intermittent arc fault by a loose wire strand or a screw which is just getting slightly loose; if you plug this in and check it the next day, it will tell you that there was an arc…even if it happened 4 hours ago?
I only use self-testing AFCI breakers. So I guess you can test if the self-test is faulty? Hmm.
OK, so the AFCI works like the GFCI test, you press the test button, and it then lets you know that yes or no, there is an arc fault.
The outlet tester is straight forward, whatever lights you get, that is the situation…. like reverse polarity, it is, or it isn’t. The GFCI test is also similar in that either the GFCI is properly working or properly wired….or it isn’t.
What about the AFCI, there must be many times you get a negative reading for an arc, but if someone plays with a plug and outlet, it could arc if a screw is just loose enough to hold a wire but not properly tight
The AFCI detection is in the circuit breaker. It is monitoring the branch circuit at all times and trips if it detects arcing. These testers simulate an arc fault, which will cause the AFCI to trip if it is working correctly.
I agree with the point about the noise, I have mine off permanently.
If you like the RT600, a similar model comes with the ET310 breaker finder. It just adds a finder transmitter which shouldn’t affect anything if you’re just using it as a GFCI tester, but I like that it docks into the back of the circuit probe.
The form factor on it makes more sense when you see some of the other country models, a lot of those plugs are pretty large.
I agree though, the design is also asking to be broken in transport too. I like the inline versions better. Klein has one with a very basic digital voltage meter, where it reads like a Clamp meter or DMM would. Kobalt has one too but it’s readout is fake, if there’s any voltage present it will read “120V.” Here’s the Klein: https://www.homedepot.com/p/Klein-Tools-GFCI-Electrical-Outlet-Tester-with-LCD-RT250/313832938
What I’d personally recommend is getting a circuit breaker finder because those come with an outlet/GFCI tester and add more capabilities for minimal cost. Klein, Uni-T, Extech, Sperry, among others make them. I like the Extech because it is adjustable (I bought mine on sale for $24): https://www.amazon.com/Extech-CB10-Circuit-Breaker-Finder/dp/B0014FNWJG
I agree – this Fluke tester is inconvenient to keep in a bag, and the audio function is simply useless (unless the outlet is in the same room as the service panel).
Reliance makes one that’s also sort of a dud in terms of being bag-friendly (it’s very large) but it makes up for that by being ear-shattering, really. Around $30 at Amazon.
Fluke says it the tester…
Thank you, *fixed*!
Has anybody used the Klein tester with the digital display?
HD has it currently priced around the same as this Fluke. Was wondering if the digital display adds any value to the traditional three lights that are on the tester.
I’ve got one. It’s noticeably bulkier than a standard outlet/GFCI tester… And it only has two lights, green for “good”, red for “bad” and the display shows the error. Definitely takes a few seconds longer to use than a standard tester. If it’s the only tool I’m carrying, it’s nice to have to verify proper voltage… But if I’m carrying it in my meter bag, it becomes redundant. The biggest downside is that it’s battery operated, and that also adds significant weight.
I have started using one of these. I actually like it less than the less complex ones, mostly because I forgot to turn it on half the time. It also needs batteries, which will probably be annoying when they die on site. All in, it probably takes 10 seconds instead of 3 seconds to check of a plug is wired correctly -annoying but trivial difference in the grand scheme of things.
The only functionality the digital display adds is the voltage at the plug. This is nice to see, and you can watch voltage fluctuate when the AC turns on. I’m sure there are some cases where this can be useful.
I end up grabbing the more simple RT210 tester most of the time just because it is easier and faster to use.
Only bought this a few months back. But I love it. I got to give my old simple tester to my building super, because he loves using them all over the apartments to ensure that the correct recepticals are connected to the correct breakers in each apartment’s breaker box. Turns a breaker on, and the tester doesn’t light up in the room it is supposed to be in? Gotta work on that receptical.
As to Me having the RT280? It’s a Godsend. I mean that with no blasphemy to anyone of devout faith. For me, this receptical tester is a thousand times easier. I’m colourblind, I’ve talked about this before on the page, and some people may be sick of hearing it. But a simpler one has lights that are not only not red or yellow, (the only colours I can see.) but that shine bright enough that the light bleeds into the sections that aren’t actually illuminated during the test, throwing me off as to what is actually working, and what isn’t.
Enter the RT280. As mentioned, 2 lights. Correct, and Wrong. Clearly marked. Plug it in, it has batteries installed, so the screen stays persistent when you pull it back out. So, if it just lights up Correct (Again, Clearly individual, no bleeding over to the “Wrong” light.) then one quick pull takes no time at all to know everything is A-Okay.
If it wires up wrong (again, colourblind, sometimes that wiring is not the standard black/white/ground combo, that can be a problem for me.) Wrong lights up, obviously all its own, and a yank of the tester into the hand shows exactly what was done wrong. A quick swap later, based on what you read on the screen… Correct Wiring! I love the Klein RT280. Will I ever be a pro electrician? Not likely, but I can at least do some home built stuff, without my weird eyes stopping me. And honestly? I think I paid $30 CAD for it. Full electronic gadget for $15 USD? For all I gain, I cannot find any sort of downside to this Receptacle Testor!
The other problem with this Klein is that it’s nearly impossible to use for outlets installed ground up.
“Receptacle swivel adapter” although I doubt you’ll be able to find a UL-listed one.
When you unplug it it shows the last reading until you reset it
It absolutely works fine, regardless of orientation. As I said, you plug it in, and look for the Correct/Wrong light. You only need to look at the results on-screen if there’s a fault.
For that? There’s batteries in it, and it stays on screen until you turn it off, or store it to memory. There’s a button for that. And if you want to recall the last result, it’ll be there the next time you activate it, but before you test anything with it.
So it really is fine no matter what. Plus, you can use straight-single-socket power cords (like the ones you find with a Computer Tower, or other large Computer equipment) modified with a standard receptical instead of the Power Supply socket. They also make them simply for outdoor use, with just a straight socket and plug on either end. If you’re lucky, you can get them with an angled plug so you can fit even closer into tight spaces. Then just test through the extension.
The RT20 is remarkably versatile compared to the standard 3 light configuration.
You could probably use one of the 12″ or smaller extension cords?
Looks like a nice upgrade from one of the old school Red-Amber/Orange outlet tester. The bright lights, and nice color difference will make it easier and safer to use. I wonder if the old school testers used orange/amber and red due to availability, or cheapness.
A lot of designs have incandescent mini bulbs, with colored plastic lenses.
The Fluke has LED indicator lights, which allows for easier color selection. But, I expect this also requires step-down and AC to DC voltage conversion, which is likely a big part of the reason for the tool’s larger size.
You got me curious enough to check my old tester, and it has tiny incandescent lights indeed. That explains a lot of stuf. Thank you very much!
Umm, aren’t they actually neon bulbs?
The LED lighting on the Fluke is great for remote inspections. Last year, most of our final inspections were done over Facetime, and I used this because the lighting was much easier to see over video.
If you do electrical for a living you should be using an Extech CT70 which does everything the Fluke does but also test for voltage drop on 15A and 20A circuits. It also measures voltage, frequency (for generators) and line impedance.
Building inspectors should be using the CT70.
Building inspectors should be using any tester that actually has a label on it that “GFCI TEST NON FUNCTIONAL IF GROUND NOT PRESENT”.
I’ve found many who do not understand the concept.
I am curious why since a GFCI does not require a connection to the grounding conductor to operate. Is it part of the internal circuitry of the tester?
If the receptacle is installed in the correct orientation, then the lights will be pointing at the floor.
Where is that in the NEC?
This Fluke looks nice. I have a 2 Kleins, including the LCD display model mentioned above, plus a couple of other brands. They are all similar and rarely will one of these stop working.
John++E brought up 2 good points, as much as I trust and like Fluke products, I would opt for another model over these if I needed to get one.
I was looking online at this Fluke model and wondering if someone can explain something to me. Both the ST120 and the ST120+ come as such as well as another model that adds -LW. Such as ST120-LW and ST120+-LW.
What is the LW?
Hmm, maybe it is an older model making this one actually “new”. Mine from 2021 is an ST120+-LW.
I don’t think it is a new model. I went to various electrical shops online. When I search Fluke ST120, I get 4 results….ST120, ST120-LW, ST120+, and ST120+-LW.
Thing is read through the descriptions and specs and do not see any mention of anything additional or different for the -LW models.
Maybe it includes text on the packaging that it is “Lowe’s exclusive”. Or it is carded differently?
Did you buy it at LoWes?
Lots of manufacturers will add a little bit to a model number to indicate who sold it.
No, I have not bought it, I just saw it on 3 different online vendors that specialize in electrical equipment and have nothing to do with Lowes. Google Fluke st120-LW or st120+-LW and you should see the LW versions available at many vendors online.
Is this really new? I’ve had one since June of 2021.
New to me, then? I spotted it last holiday season at Lowe’s, but didn’t see it anywhere else. It then disappeared and reappeared recently.
Since you say you have one, how do you like it?
Pretty much as other posters have commented… the form factor is weird for storage. The beeper is annoying. The LEDs are great for video remote inspections, and even if the receptacle is oriented properly, the LEDs do not really point “down”. The build quality is great, so for the price I think it’s a good deal. Despite fitting weird in my tool bag, I still carry and use it (along with the Klein ET310 breaker tracer with tester), with older ones (like Sperry, Klein) being left in my box at home. I usually carry the lead extenders for use with the breaker tracer and those can be used with this it doesn’t block the receptacle. They’re a pigtail extension, a lamp base adapter, and spring clips to a receptacle. Anyone testing or tracing circuits should have them to adapt to non-receptacle outlets.
10 hours ago
So, you plug this in and if there is an arc fault detected, it will let you know.
A bad arc fault which is almost constant, it will detect. What about an intermittent arc fault by a loose wire strand or a screw which is just getting slightly loose; if you plug this in and check it the next day, it will tell you that there was an arc…even if it happened 4 hours ago?”
No, this won’t detect arc faults. It will test a breaker that has arc fault detection.
Yes, I understand now. I saw a comment last night…maybe JoeM, which basically stated like you. This tests if your arc fault breaker is working, in the same way that the GFCI also, lets you know that your GFCI breaker/outlet is working.
I don’t believe it is to test your breakers or GFCI receptacles. It’s to test if the receptacle has GFCI/AFCI protection (to ensure code compliance). The breakers and receptacles have test functions on them already, but that doesn’t mean that receptacles that require protection are actually protected (think receptacles protected from another GFCI, or receptacles in a bedroom that must be protected by AFCI).
It’s for verification of receptacles that aren’t obviously protected.
Simply tests if it is GFCI compliant. Doesn’t actually test for faults in GFCI or AFCI. This thing literally just tests if you have wired a receptacle correctly. You can push the test button, and it’ll run to see if there is some sort of breaker or power protection somewhere along the line, but unless that receptacle literally has the test and reset safety buttons that have a built-in breaker, this will not trigger a GFCI or AFCI test. And yes, it will display a number at which the receptacle is set to trigger an overload cutoff.
If you’re wondering… I just tested the Klein RT280 on a power receptical I built into my desk, simple standard type. Then I went to the bathroom where there was a GFCI safety triggered receptacle. I ran the test on both, the one under my desk blinked “Correct” for a while, and spat out some numbers it was set to (it appears to be 6Amps it will cut out at my desk… Dunno where the breaker is for that, I have that receptacle built into the desk like a power bar, which is plugged into another power bar with a circuit breaker… but that plugs into an old UPS that needs a new battery, and that plugs into the wall, which would be connected to the breaker box. Since my entire room did not cut out during the test, I can only think the GFCI test reported there was a breaker on the power bar and old UPS that were passing the test. And didn’t test all the way to the Breaker Box.) and then the Bathroom was a receptacle directly in the wall, set to pop if too much moisture causes a circuit fault for whatever is plugged in. Testing the GFCI on that receptacle with the RT280 caused the built in receptacle to pop the safety, just like hitting the test. While it was still plugged in, it gave tons of info on how much amperage it took to trigger the circuit breaker in the receptacle, plus how effective it was at cutting over from “Correct Wiring” to “Faulty Wiring” as one would expect from a cut off circuit. Pushing the Reset button on the receptacle then switched the tester back to “Correct Wiring” as is normal.
And to whoever thought this Klein RT280 doesn’t work well for recepticals not in the ground-up position? The bathroom receptical is ground to the left, two receptacles standard side by side, mounted normally, GFCI test buttons between receptacles. The RT280 works in any orientation. It also needs to be powered on before plugging it in, so there’s no excuse in the world for thinking it can’t be used with the screen facing away from you. It holds the reading when you pull it out of the receptacle, and you just have to look at the screen. It isn’t powered by the receptacle you test, so there’s no excuse to think it has orientation limits.
I’ve had one for about a year or so not new… Also someone said it’s annoying to have to unplug things because it needs both outlets .. How do you change the out let if it’s bad? I just unplug everything.