As an Amazon Associate, Akermin earns from qualifying purchases. Product links on this page are affiliate links.
KLEIN TOOLS · Klein Tools ET310KIT AC Circuit Breaker Finder Kit | Electric Tester, GFCI Tester, Leads, Adapters and Case
View on AmazonPrice and availability are shown on Amazon and can change at any time.
A two piece breaker finder: a transmitter that plugs into the outlet you are tracing and a receiver you sweep across the panel, which gives visual and audible indications when it is over the right breaker. The transmitter also works as a ground fault outlet tester, and the kit adds a light socket adapter, a three prong to two prong grounding adapter and an alligator clip adapter for bare conductors. The receiver is stated to work on 90 to 120 V AC circuits, and that single figure is the whole buying decision, because it excludes every 240 V circuit in your panel.
One quantity in five bullets, and it is the right one
Count the numbers in this listing. There is 90 to 120 V AC, and there is a three prong to two prong adapter. That is all. No sensitivity, no range, no battery life, no dimensions, no tolerance, no measurement category.
Normally that would be the complaint. Here it is worth starting from the opposite direction, because of all the figures a breaker finder could have published, the voltage window is the one that actually changes who should buy it. Sensitivity affects how long the sweep takes. The voltage window decides whether half the circuits in a domestic panel are reachable at all.
So the listing is thin, and it is thin in a way that still answers the first question. That is better than the common pattern in this category, where five bullets of adjectives surround a tool whose limits you discover on site.
The rest of the page is descriptive rather than specified: accurate identification, clear indications, hassle free locating. Those sentences tell you what the tool is for. Only the voltage range tells you where it stops.
Why every 240 volt circuit in the panel is out of scope
A North American domestic panel is fed by two line conductors and a neutral. Ordinary outlet and lighting circuits take one line and the neutral, giving 120 V nominal, and sit on a single pole breaker. Heavy loads take both lines, giving 240 V nominal, and sit on a double pole breaker that occupies two slots.
The transmitter is the half that has to be connected to the circuit under test, and the published window stops at 120 V. So the circuits you cannot trace with this kit are the range, the oven, the clothes dryer, the water heater, a well pump, a workshop compressor and an electric vehicle charger. Those are also, inconveniently, the circuits most often mislabelled in a panel.
It is worth being clear that this is a limitation of the method rather than a defect. Finding a double pole breaker needs either a transmitter rated for the higher voltage and a matching receptacle pattern, or a hard wired connection at the appliance, which is a different class of tool and a different safety conversation.
It also explains why the bottom of the range is 90 V rather than 100 or 110. A 120 V nominal supply sags under load and varies with distance from the transformer, and a long branch circuit feeding a working appliance can sit well below nominal. Publishing 90 as the floor says the transmitter keeps working on a tired circuit, which is the realistic case. Our explainer on what a measurement category rating means covers the other half of plugging an instrument into live wiring.
How a transmitter and receiver pair narrow a breaker down
Understanding the mechanism changes how you use it, and the listing does not explain it.
The transmitter does not send a radio message. It superimposes a coded low power signal on the circuit conductors themselves. That signal runs back through the branch circuit to the breaker, and every conductor carrying an alternating current produces a magnetic field around itself that varies with the current. The receiver is a tuned coil listening for that particular code in the field.
Three practical consequences follow. First, you are locating the conductor, not the switch, so a strong indication can appear over a neighbouring breaker whose cable happens to run alongside the target on its way into the busbar. Sweeping in both directions and watching for the peak rather than the first response is how you deal with that. Second, the signal weakens with distance and with intervening steel, so working with the panel cover off, where that is safe and permitted, gives a far clearer result than sweeping a closed door. Third, nothing about the method requires the breaker to be on the same phase as anything, which is why a single transmitter can find any 120 V circuit in the box.
Against the alternatives, that is a lot less invasive than switching breakers off one at a time and walking back to see what died. Our comparison of circuit breaker finders looks at how the indication schemes differ between units.
The transmitter earns its keep twice over
The design decision worth praising is putting the ground fault outlet test inside the transmitter.
The transmitter is already going into the outlet. It already has to reference line, neutral and ground to inject a signal, which is precisely the wiring configuration a receptacle tester reads. So the ground fault test adds almost nothing to the tool and gets performed on every job instead of on the jobs when you remembered the other device. Protective devices that have never been exercised are the ones that seize, so a test you actually run beats a better test you skip.
The three adapters answer three separate access problems rather than padding the box. The light socket adapter covers the common case of a ceiling fixture on a circuit with no accessible outlet, which otherwise means pulling a switch plate. The three prong to two prong adapter covers older ungrounded receptacles, where the transmitter still needs a return path. The alligator clip adapter covers a conductor with no receptacle at all, such as a junction box or a device you have disconnected, which is also the only route to a circuit that does not terminate in a standard outlet.
Taken together, the kit is less about the finder and more about the number of places you can attach it. That is usually what decides whether a tool gets used.
The blank rows on a breaker finder specification
| Question a buyer asks | The answer in the bullets |
|---|---|
| Which circuits is it rated for | 90 to 120 V AC |
| How does it indicate a match | Visual and audible cues on the receiver |
| Does it test ground fault devices | Yes, built into the transmitter |
| Can it work from a light fixture | Yes, light socket adapter supplied |
| Can it work on an ungrounded outlet | Yes, three prong to two prong adapter supplied |
| Can it work on a bare conductor | Yes, alligator clip adapter supplied |
| Sensitivity or depth through a closed panel door | Not stated in the listing bullets |
| Behaviour with tandem or arc fault breakers | Not stated in the listing bullets |
| Handling of a shared neutral on a multiwire circuit | Not stated in the listing bullets |
| Battery type and expected life | Not stated in the listing bullets |
| Measurement category rating of the transmitter | Not stated in the listing bullets |
| Whether it traces a de-energised conductor | Not stated in the listing bullets |
Two of those blanks are worth more than the others. The missing measurement category rating is awkward on a device whose whole purpose is to be plugged into a live circuit, and a category rating is the only figure that describes what an instrument survives when the supply throws a transient at it.
The tandem breaker question is the practical one. Panels in older houses are frequently filled out with tandem breakers, two switches sharing one slot, and their conductors enter the box inches apart. That is the hardest case for a magnetic pickup and the one a buyer with a full panel will meet immediately. Silence on the point is not the same as failure, but it leaves you to find out.
The kit this replaces, and the one it does not
Buy this if your work is 120 V branch circuits in homes and light commercial buildings and you keep meeting unlabelled panels. The voltage floor at 90 V suits a real circuit under load, the transmitter does two jobs, and three adapters mean you can inject a signal from a fixture, an old ungrounded outlet or a bare pair, which covers nearly everything a domestic panel feeds.
Do not buy it as your only tool if you regularly work on 240 V appliance circuits, because the stated range excludes them and those are the circuits most often labelled wrong. Do not buy it for a 230 V system, since neither the voltage window nor the outlet pattern fits. And do not expect it to follow a cable: identifying a breaker and tracing a dead conductor through a wall or under a lawn are different problems, and the second one needs a tracer, as our round up of circuit tracers explains.
Within the window it publishes, this is an honest and well equipped kit. The one number on the page is the one you have to read.
Recommended Tools
Products shown because their documented specifications fit this guide. Price and availability are on Amazon and can change.
Frequently Asked Questions
Will this find the breaker for a 240 V circuit?
Not according to the one figure the listing publishes. The receiver is described as locating breakers on 90 to 120 V AC circuits, and a 240 V circuit is outside that window. The transmitter is the part that has to live on the circuit and inject the signal, so the limit is about what you can safely plug it into rather than what the receiver can hear. That puts the range, the dryer, the water heater and an electric vehicle charger beyond this kit.
How does a breaker finder actually identify the right breaker?
The transmitter plugs into the circuit and superimposes a coded signal on it. That signal travels back along the circuit conductors to the panel, and any conductor carrying an alternating current radiates a magnetic field around itself. The receiver is a tuned inductive pickup: swept along the row of breakers it responds most strongly over the one whose conductor carries the code. You are not detecting the breaker, you are detecting the cable behind it, which is why sweeping slowly and repeating the pass in both directions matters.
Will it work on a 230 V supply outside North America?
The stated range says no. A 230 V nominal circuit is roughly double the top of the published window, and nothing in the bullets describes a second range or a selectable mode. There is also a physical problem before the electrical one, since the transmitter is built around a North American grounded outlet and the kit includes a three prong to two prong adapter for that pattern. Treat this as a tool for 120 V nominal systems.
What does the GFCI test in the transmitter add?
It uses a trip that was going to happen anyway. The transmitter has to be plugged into the outlet whose circuit you are tracing, so putting a ground fault test in the same body means you check the protective device and the wiring condition at the same outlet, on the same visit, without reaching for another tool. A ground fault device that has never been exercised is the one most likely to have seized, so a test you will actually perform is worth more than a better one you will not.
Is a breaker finder the same thing as a circuit tracer?
No, and the difference is whether the conductor is live. A breaker finder of this type needs an energised circuit to plug into, and answers one question: which breaker feeds this outlet. A tracer puts its own signal onto a dead conductor and follows the path of that conductor through walls, floors or ground, which is a different job needing a different instrument, such as an underground wire locator for buried runs. If your problem is the route of a cable rather than the identity of a breaker, this is the wrong tool.
What would you want the listing to publish?
A sensitivity or depth figure, so you know whether the receiver works through a closed steel panel door. The behaviour with tandem breakers, where two switches share one slot, because adjacent conductors are the hard case. Whether it distinguishes a shared neutral on a multiwire branch circuit. The battery type and expected life in both halves. And a measurement category rating, since the transmitter is a device you plug into a live outlet.
Affiliate disclosure: Akermin earns a commission from qualifying Amazon purchases made through links on this page. Our editorial picks are based on documented specifications and owner feedback, not commissions.