How to Lock Out a Breaker Using a Circuit Breaker Lockout Device

A breaker in the OFF position does not prove that a circuit is safe to work on. Before working on or near exposed deenergized electrical parts, workers must follow the applicable isolation and lockout/tagout procedure, and a qualified person must verify absence of voltage at the parts to which employees will be exposed.

A compatible breaker lockout device helps prevent operation of the selected breaker while the lockout/tagout procedure remains in effect. The installation method depends on the breaker's handle design, pole arrangement, available clearance, and the manufacturer's instructions.

Key Takeaways

• Apply the OSHA requirements appropriate to the work. Section 1910.333(b)(2) addresses electrical isolation, lockout/tagout, and verification, while 1910.147 covers hazardous-energy control during machine servicing within its scope.

• A properly installed breaker lockout device helps prevent operation of the selected breaker, but it does not independently establish that all electrical parts are deenergized.

• Select a breaker lockout device based on handle design, tie-bar configuration, opening dimensions, and available clearance, not pole count or breaker protection type alone.

• For electrical work, a qualified person must verify absence of voltage at the circuit parts employees will be exposed to; a locked breaker or equipment tryout alone does not prove they are deenergized.

 

What Is a Circuit Breaker and How Does It Work?

A circuit breaker is an electrical switch designed to automatically stop the flow of electricity when a fault, such as an overload or short circuit, occurs. Breakers are installed in electrical panels, where they connect the main bus bars to the individual circuit wires that distribute power throughout the electrical system. Each breaker monitors the electrical current flowing through its circuit. If the current exceeds safe levels, the breaker "trips" and opens the circuit to stop the flow of electricity.

Traditional circuit breakers are mechanical switches that operate with a spring-loaded mechanism and a thermal or magnetic trip unit to detect faults and disconnect power. Modern circuit breakers, on the other hand, often include electronic trip units and more precise sensors. These allow for faster response times and better coordination with complex electrical systems.

Circuit Breakers vs. Fuses vs. Disconnects

Circuit breakers, fuses, and disconnects are all devices used to control and protect electrical circuits, but they work differently:

• • Circuit Breakers
    • Automatically trip to stop power during an overload or short circuit.
    • Can be reset after the fault is cleared.
    • Commonly used for ongoing circuit protection and easy restoration.
  • Fuses
    • Contain a metal wire that melts when overloaded, permanently breaking the circuit.
    • Must be replaced once blown.
    • Provide simple, one-time overcurrent protection.
  • Disconnects (Safety Switches)
    • Manually isolate equipment from the power source.
    • Do not trip automatically.
    • Used for maintenance or emergencies to provide a visible break in the circuit.

 

Breaker Features That Determine Lockout Device Compatibility

How to Lock Out a Breaker?

For electrical work on conductors or equipment in electric-utilization installations, OSHA 29 CFR 1910.333(b)(2) addresses deenergizing, lockout/tagout, and verification. OSHA 1910.147 applies to hazardous energy control during machine servicing within its scope. Follow the requirements that apply to the work being performed.

To lock out a breaker, identify the correct circuit, shut down the equipment, and isolate the required energy sources under the equipment-specific procedure. With the breaker OFF, fit a compatible lockout device and secure it with your personal safety padlock and tag. Check that the device is firmly seated, then complete the required isolation verification before work begins.

Since breaker designs vary, choosing the correct breaker lockout device matters. Be sure to check out our Breaker Lock Solution Guidelines to find the right TRADESAFE Breaker Lockout Device for your specific breaker model and number of poles.

 

How to Install a Breaker Lock?

The steps below cover fitting the lockout device. Use them within your equipment-specific lockout/tagout procedure, which must also address other energy sources, stored energy, and verification. Choose the instructions for your device and follow its manufacturer’s directions.

Clamp-On Breaker Lockout Devices

A clamp-on circuit breaker lockout is available in different sizes to accommodate medium to oversized circuit breakers without lockout holes in the toggle switch. Follow these steps for a proper clamp-on circuit breaker lockout installation:

1. Put the circuit breaker in the OFF position.

2. Place the clamp-on circuit breaker lockout device over the circuit breaker switch toggle.

3. Rotate the thumb wheel clockwise to secure the lockout device.

4. Close the lid and attach a lockout tagout padlock and tag to secure the lockout.

Universal Circuit Breaker Lockout Devices

The TRADESAFE universal circuit breaker lockout fits compatible tie-bar handles up to 7/8 inch thick. Check the handle dimensions and available clearance before fitting it. To install it:

1. Put the circuit breaker in the OFF position.

2. Position the device on the compatible tie-bar handle.

3. Tighten the thumbscrew until the device is firmly seated.

4. Insert your safety padlock through a compatible shackle hole on the side of the device, then attach the tag.

Miniature Circuit Breaker Pin Lockout Devices

Miniature circuit breaker pin lockouts secure compatible breakers through designated openings. For TRADESAFE models, Pin-In Standard uses inward-facing pins and accommodates up to 1/2-inch hole spacing; Pin-Out Standard uses outward-facing pins and accommodates up to 3/8-inch hole spacing; and Pin-Out Wide uses outward-facing pins and accommodates up to 11/16-inch hole spacing. Verify the breaker's opening configuration and the device's fit dimensions before installation. For these push-button models:

1. Put the mini circuit breaker in the OFF position.

2. Press the button to move the pins into the installation position.

3. Align the pins with the breaker’s compatible openings, then release the button to engage them. Check that both pins are seated.

4. Attach a lockout tagout padlock through the lockout device hole to complete the lockout.

Tie Bar Lockout Devices

A tie bar lockout device is specifically affixed to multi-pole breakers that have tie bars connecting two or more toggles. To install it correctly, here’s what you need to do:

1. Place the mini circuit breaker in the OFF position.

2. Position the metal clip under the tie bar and between the poles.

3. Rotate the thumb wheel clockwise to secure the lockout device onto the circuit breaker.

4. Insert a TRADESAFE padlock through the hole to secure the device in the locked position.

Breaker Blocker Kit

A breaker blocker kit uses adhesive-backed mounting rails and a blocking rod for compatible oversized or irregularly shaped 480/600V breaker switches. Check the mounting space and breaker configuration before installation. For the linked TRADESAFE kit:

1. Put the circuit breaker in the OFF position.

2. Prepare the mounting surface and install the two adhesive-backed rails beside the breaker according to the kit instructions.

3. Position the red OFF-position blocking rod through the rails so it restrains the breaker handle in the OFF position.

4. Secure the assembly with compatible safety padlocks and attach the required tag.

5. Check that the rails and rod are secure before completing isolation verification.
   

The green rod holds a compatible breaker ON; it is not the rod to use for this OFF-position maintenance lockout.

Common Mistakes in Using Breaker LOTO Devices and How to Avoid Them

In the lockout tagout of circuit breakers, one common mistake is not fully engaging the breaker lock device’s mechanism. I once visited a manufacturing facility where the authorized employee applied a breaker thumb-screwed type lockout device, but didn’t tighten it securely. It slipped off when the panel was bumped, leaving the breaker off but unlocked.

This confused some workers who thought the circuit was back in service, while others believed it was still under maintenance. Luckily, no one was hurt, but it was a close call that led to a retraining session for the entire crew.

Another frequent error is using the wrong lockout device for the type of breaker. If the wrong type is used, the breaker handle might not be fully restrained, which gives a false sense of security and defeats the entire purpose of the lockout. Remember, the right lockout device depends on the type of breaker, the toggle style, and the environment you're working in.

 

How to Ensure a Successful Lockout

Checking that the lockout device is secure, verifying that the equipment cannot restart, and testing for absence of voltage are separate checks. Locking out one branch breaker does not necessarily deenergize the panel, its supply-side components, or adjacent circuits.

For electrical work, a qualified person must use suitable test equipment to verify that the circuit parts employees will be exposed to are deenergized, including checking for possible backfeed or induced voltage. Other exposed electrical parts must be treated as energized unless they have also been properly isolated and verified.

I've seen workers skip voltage verification after applying the lockout device. Some assume that once the breaker is turned off and locked, the circuit is safe, especially if the panel is labeled. In reality, labeling can be inaccurate, or the wrong breaker may have been locked out, leaving the circuit still energized. In other cases, teams rush to complete the task and see voltage testing as an extra step rather than a requirement.

Expert Insights

“In my experience, the only safe way to test that electrical equipment is safe to work on is using a voltage indicator, in conjunction with a proving unit, before and after testing for dead, to prove the voltage indicator is working correctly. Non-contact devices, such as volt sticks or pens, cannot be relied upon for this purpose. If you’re going to put tools or your hands on any electrical equipment, you need to be absolutely certain it’s safe to work on before you touch it…” — Mark Platten, a Commissioning, Compliance & COHE Manager with over 35 years’ experience, shared his thoughts on “What are the Most Effective Ways to Verify Electrical Lockout and Tagout Procedures?”

 

Breaker LOTO Installation FAQs

How do you disable a breaker?

To lock out a breaker, identify and isolate the correct circuit under the applicable procedure, place the breaker in the OFF position, and apply a lockout device compatible with its handle configuration. Secure the device with the required padlock and tag, then complete the prescribed verification steps. For electrical work involving exposed circuit parts, a qualified person must verify absence of voltage at the parts employees will be exposed to before work begins.

How to unlock a breaker lock?

Normally, the employee who applied the lock and tag removes them. If that employee is unavailable, removal must follow the employer’s specific procedure under the applicable OSHA requirements, including checks to locate the employee and informing them before they resume work. To unlock, remove the padlock and tag, then take off the breaker lockout device. This should only be done after the work is complete, and it’s been confirmed that it’s safe to re-energize the equipment.

Can one lockout device fit all breakers?

No. Lockout devices must match the specific type and size of the breaker. For example, miniature circuit breakers often require pin-in or pin-out devices, while multi pole breakers with a tie bar need a tie bar lockout. Using the wrong device may fail to secure the breaker properly, compromising safety.

Is it OSHA compliant to use non-branded lockout devices?

OSHA does not require breaker lockout devices to come from a specific brand. Under 29 CFR 1910.147(c)(5), lockout devices used within that standard's scope must meet applicable requirements for durability, standardization, substantial construction, and identification. The device must also be compatible with the breaker and used as part of the employer's applicable energy-control procedure. Choosing a particular brand does not, by itself, establish OSHA compliance.

What happens if I skip installing a lockout device during repairs?

Failing to apply required lockout/tagout controls can expose workers to unexpected re-energization, electric shock, arc flash, and potentially fatal injuries. OSHA generally requires a lock and tag on disconnecting means used to deenergize fixed electrical equipment covered by 29 CFR 1910.333(b)(2), subject to specified exceptions. When a tag is permitted without a lock, additional protective measures may be required. Always follow the requirements applicable to the equipment and work being performed.