Cool Tool Alert: The Klein Circuit Breaker Finder/GFCI Tester at Last Best Tool

Brendan Lamothe

Key Takeaways

  • The tool simplifies finding the right breaker for a specific circuit.
  • It doubles as a GFCI tester to detect common outlet problems.
  • The Klein Tools ET310 is a cost-effective investment at approximately $40.

Overview of Klein Tools Digital Circuit Breaker Finder

Tool Components

The Klein Tools Digital Circuit Breaker Finder comprises a transmitter and a receiver. The transmitter plugs into an outlet and sends a signal through the electrical circuit. The receiver detects this signal, helping you identify which breaker controls the specific outlet.

Here's a brief overview of the components:

  1. Transmitter:

    • Plugs into standard outlets.
    • Functions as a GFCI tester.
    • Equipped with a trip switch to test GFCI circuits.
  2. Receiver:

    • Handheld device designed for easy use.
    • Moves along the breaker panel to detect the transmitter's signal.

Design and Ergonomics

The design focuses on user-friendly features. The receiver's shape ensures a firm grip, allowing for precise navigation along the breaker panel. The overall setup is intuitive, minimizing the need for additional tools or assistance.

Key design features include:

  • Ergonomic grip: Ensures secure handling.
  • Compact size: Easy to maneuver in tight spaces.
  • Clear indicators: Provide visual cues for signal strength and GFCI status.

This tool streamlines the process of identifying circuits and troubleshooting electrical issues, making it a valuable addition to any toolkit.


Circuit Identification Process

The Klein Tools Digital Circuit Breaker Finder consists of two main parts: a transmitter and a receiver. Begin by plugging the transmitter into the outlet you wish to test. Turn on the receiver and move it slowly up and down the breaker panel. The receiver identifies the specific circuit connected to the transmitter by detecting signal variations.

  1. Plug the transmitter into the outlet.
  2. Power on the receiver after the transmitter is plugged in.
  3. Move the receiver along the breakers.
  4. Look for signal changes indicating the correct breaker.
  5. Verify by flipping the identified breaker off and on.

GFCI Testing Capability

This tool not only locates circuits but also tests GFCI outlets.

Steps for GFCI Testing:

  1. Plug in the transmitter: Insert it into a GFCI outlet.
  2. Test for faults: The device can detect wiring issues, indicated by the pattern of lights.
  3. Trip the GFCI: Use the trip switch to test the operation of the GFCI circuit.
  4. Reset as needed: Ensure the transmitter is powered back after each test cycle.

The tester identifies common wiring problems and helps ensure GFCI outlets are functioning correctly, providing an extra layer of safety in your electrical system.

Practical Applications and Benefits

The Klein Tools Digital Circuit Breaker Finder, model ET310, offers several practical applications and benefits for anyone dealing with electrical systems.

Accurate Circuit Identification

Using both a transmitter and a receiver, this tool allows you to precisely locate the circuit breaker associated with a particular outlet. This eliminates the guesswork and potential hassle of manually flipping breakers while trying to identify the correct one.

GFCI Testing

The built-in GFCI tester provides additional functionality. You can easily identify common wiring problems and test GFCI outlets directly. The tool will indicate potential issues through a series of lights and allow you to trip the GFCI circuit using the trip switch.

Common Problems Identified by GFCI Tester:

  • Open Ground
  • Open Neutral
  • Open Hot
  • Hot/Ground Reversed
  • Hot/Neutral Reversed

Simplifies Troubleshooting

Previously, you might have relied on methods like walkie-talkies or running extension cords to identify circuits. The Klein Tools ET310 simplifies this by providing a clear and direct way to find the right breaker without additional help or cumbersome setups.

Cost-Efficient and Convenient

Priced at about $40, this tool is a cost-effective solution compared to standard GFCI testers, which can cost between $10 and $20 and often lack the ability to trip the GFCI circuit. Investing in the ET310 not only saves time but also provides better value in the long run.

Potential for Personal Utility and Profit

You might even consider renting this tool to neighbors, potentially turning it into a small source of income. For instance, a simple $5 rental fee is a small investment for quality and accuracy in circuit identification and GFCI testing.

Easy to Use

The ET310's design ensures ease of use. You plug the transmitter into the outlet, power up the receiver, and then move it along the breaker panel until the signal indicates the correct breaker. The tool then helps you confirm the circuit by cutting power to the transmitter and repeating the test.

This tool is highly recommended for anyone who frequently works with electrical breakers or wants to ensure the safety and functionality of their GFCI outlets.

Operational Guide

Initial Setup

  1. Plug the Transmitter into the Outlet: Begin by plugging the transmitter into the outlet powering the light or device you want to trace.
  2. Power Up the Receiver: Once the transmitter is plugged in, switch on the receiver. Remember to reset the receiver each time you flip the breaker.

Transmitter and Power Considerations

  • Dual Functionality: The transmitter acts as a circuit finder and a GFCI tester.
  • GFCI Testing: Use the trip switch on the transmitter to test GFCI outlets. This can help identify faulty outlets and diagnose common wiring issues.
  • Signal Strength: When identifying the correct breaker, ensure the transmitter remains powered, as shutting off power weakens the signal.

Circuit Finder Usage

  1. Initial Scanning: Slowly move the receiver down past all the breakers to start the learning process for detecting the transmitted signal.
  2. Identifying the Breaker:
    • Observe for any change in the receiver signal as you move past each breaker.
    • If the receiver picks up a signal and the light or device turns off, you've likely found the correct breaker.
  3. Verification:
    • Restart the transmitter and repeat the process to confirm the correct breaker.
    • Ensure the device remains operational to maintain a strong signal for easier identification.

By following these steps, you can efficiently locate specific circuits and test GFCI outlets using the Klein Tools ET310 Digital Circuit Breaker Finder.

Tool Limitations and Clarifications

When using the Klein Tools Digital Circuit Breaker Finder, you should be aware of a couple of key limitations. First, the receiver does not test for live electrical power. Avoid assuming that the receiver can detect active voltage just by proximity. This tool is purely for locating circuits and identifying GFCI issues.

Important Points to Consider:

  • Transmitter and Receiver Setup: The transmitter must be plugged into an outlet, and the receiver needs to be powered on after the transmitter is connected. If you switch the breaker on and off, you'll need to reset the receiver each time.

  • Signal Strength: Once the breaker controlling the outlet is turned off, you may notice a weaker signal from the transmitter. This happens because the transmitter no longer has power. Always restart the receiver in these cases to continue accurate detection.

  • Secondary Tools: This device should not replace your non-contact voltage tester. Always use the appropriate tool to ensure safety when dealing with live circuits.

In summary, understanding these limitations and clarifications will ensure effective and safe usage of the Klein Tools Digital Circuit Breaker Finder.

Comparative Analysis and Pricing

Comparing the Klein Tools Digital Circuit Breaker Finder (ET310) to standard GFCI testers highlights several distinctions. The ET310 includes both a transmitter and a receiver. Additionally, it serves as a GFCI tester with a trip switch to test GFCI circuits or outlets.

Design and Features Comparison:


Klein Tools ET310

Standard GFCI Tester


Transmitter and Receiver

Typically one unit

GFCI Testing

Yes, with trip switch

Yes, but often without trip switch

Circuit Identification

Yes, identifies specific breakers

No, does not identify breakers

Voltage Detection

No non-contact voltage detection


Price Range



Additional Features

Combination of functions

Basic GFCI testing

The ET310 is priced around $40 at major retailers, making it a reasonable investment for its multifunctional capabilities. Standard GFCI testers, which generally lack the ability to identify specific breakers and may not include trip switches, range from $10 to $20.

Benefits of Klein Tools ET310:

  • Multifunctional Tool: Combines circuit identification and GFCI testing.
  • Ease of Use: Simplifies identifying which breaker controls a specific outlet.
  • Additional Utility: The trip switch tests GFCI circuits effectively.

Considering these factors, the Klein Tools Digital Circuit Breaker Finder is a valuable tool for anyone dealing with electrical breakers frequently. The added utility and functionality make it worth the higher price point compared to basic GFCI testers.

Closure and Additional Tips

Always remember to power up the receiver after plugging in the transmitter. Reset the receiver every time you click the breaker on and off. It's essential for accurate readings.

Pay attention to signal strength. When moving the receiver down the breaker panel, note any changes. A clear, consistent signal suggests the correct breaker.

The ET310 is not a non-contact voltage sensor. Don’t use it to test for active electrical power.

Keep in mind that standard GFCI testers don't have trip switches. Investing in the ET310, which includes this feature, offers more functionality.

Consider renting your tool to neighbors. It could potentially earn you some extra cash.

For reference:

  • Price: Approximately $40
  • Model: Klein Tools ET310
  • Features: Circuit breaker finder, GFCI tester with trip switch