Circuit breaker finder
Klein Tools ET310
Transmitter-and-receiver pair that maps an outlet to its breaker, with a receptacle tester built into the transmitter.
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Best for
Labeling a panel without two people and a lot of shouting
Specifications
| Method | Plug-in transmitter + handheld receiver |
|---|---|
| Extras | Built-in GFCI receptacle tester |
| Operation | Auto-learning: scan the panel once to learn it, then again to find the breaker |
| Voltage | 90–120 V AC circuits only |
Specifications as published by Klein Tools. Confirm against the current spec sheet before buying — manufacturers revise models without renaming them.
What's good
- Turns panel labeling from an afternoon into an hour
- Doubles as a receptacle tester, so it replaces a tool rather than adding one
What's not
- 120 V circuits only — it won't trace a 240 V breaker
- Tight, densely packed panels still take patience — follow the learn-then-scan sequence exactly
Our verdict
The tool that pays for itself the first time you label a panel properly. An accurate directory is required by the NEC and it is the single cheapest safety improvement most homes can make. See our panel labeling guide for how to record the results so they survive the next owner.
Compare with the alternatives
- Klein Tools NCVT-3P — confirming a circuit is dead before you open a device or box
- Fluke 1AC-A1-II VoltAlert — a simple, rugged live/dead check on 120 v and 240 v branch circuits
- Sperry Instruments GFI6302 — checking every outlet in a house quickly for miswiring
- Klein Tools RT250 — diagnosing voltage drop or a flaky circuit, not just wiring order
- Fluke 117 — anyone who will do this more than once a year
- Fluke 323 — measuring what a hardwired circuit actually draws, even in a crowded panel