Understanding the Ballast Bypass (Type B) LED Retrofit
In commercial and industrial lighting upgrades, the ballast bypass—commonly referred to as a Type B retrofit—is the preferred method for converting fluorescent fixtures to LED. By removing the ballast from the circuit, facilities eliminate a common failure point and allow LED tubes to operate directly from line voltage.
This approach improves reliability, reduces energy loss associated with aging ballasts, and simplifies long-term maintenance. Proper execution, however, requires a clear understanding of tube wiring configurations and fixture socket requirements.
Role of the Ballast in Fluorescent Fixtures
A ballast is a legacy electrical component used in fluorescent lighting systems to regulate current and provide the initial voltage required to start the lamp. Over time, ballasts become a primary source of flicker, audible noise, and fixture failure.
LED tubes contain their own internal drivers and do not require a ballast. Removing the ballast eliminates unnecessary power losses and reduces the number of components that can fail.
Planning a Type B LED Retrofit
Before any wiring changes are made, the LED tube wiring configuration must be confirmed. Type B LED tubes are available in single-ended and double-ended designs, and each requires a different wiring approach.
- Type B (Direct-Wire) LED tubes
- Non-contact voltage tester
- Wire cutters and strippers
- Commercial-grade wire connectors
- UL-recognized retrofit warning labels
Power Isolation and Safety
All power must be de-energized at the circuit breaker prior to opening the fixture. A non-contact voltage tester should be used at the fixture to verify the absence of voltage before accessing internal wiring.
Failure to properly isolate power presents serious shock and fire hazards in commercial retrofit work.
Removing the Existing Ballast
After removing the fluorescent lamps and raceway cover, the ballast and associated wiring will be exposed. Cut the supply and lamp wires as close to the ballast as practical and remove the ballast from the fixture.
Ballasts manufactured prior to 1979 may contain PCBs and must be handled and disposed of in accordance with hazardous waste regulations.
Wiring Tombstone Sockets for LED Tubes
This step is critical and depends on the LED tube design.
- Single-Ended Type B LED Tubes: Line (hot) and neutral conductors are connected to opposite pins on the same tombstone. Non-shunted sockets are required. The opposite end of the fixture provides mechanical support only.
- Double-Ended Type B LED Tubes: Line conductors are connected to one end of the fixture, and neutral conductors are connected to the opposite end. Shunted sockets are commonly acceptable in this configuration.
All connections must be mechanically secure and electrically insulated, with no exposed conductors.
Labeling and Final Verification
Once wiring is complete, affix the retrofit warning label inside the fixture housing. This label is required by electrical codes to alert future maintenance personnel that the fixture is wired for direct line voltage and is no longer compatible with fluorescent lamps.
After reassembly, restore power and verify proper operation. LED tubes should illuminate immediately without flicker. In large installations, light levels should be confirmed using a lux meter to ensure compliance with applicable workplace illumination standards.
Related Commercial Lighting Categories
A properly executed ballast bypass retrofit simplifies fixture wiring, improves reliability, and creates a long-term LED lighting system suitable for demanding commercial and industrial environments.
Frequently Asked Questions
What is a ballast bypass Type B LED retrofit?
A ballast bypass, also called a Type B retrofit, converts a fluorescent fixture to operate LED tubes directly from branch-circuit line voltage by removing the ballast from the circuit. This removes a common failure point, reduces ballast-related losses, and simplifies long-term maintenance.
What does a ballast do in a fluorescent fixture?
A fluorescent ballast regulates lamp current and provides the required starting conditions for the fluorescent lamp. As ballasts age, they can introduce flicker, audible noise, overheating, and intermittent lamp operation. LED tubes do not require a fluorescent ballast because the tube contains its own internal driver electronics.
What should be verified before starting a Type B retrofit?
Confirm the LED tube wiring configuration before any wiring changes. Type B tubes are commonly single-ended or double-ended, and the fixture wiring method must match the tube instructions. Also verify fixture condition, lampholder integrity, conductor insulation condition, and available grounding continuity within the fixture.
How do you isolate power safely before opening the fixture?
De-energize the branch circuit at the breaker, apply lockout and tagout procedures when required, and verify absence of voltage at the fixture using appropriate test equipment before touching any conductors. Do not rely on wall switches as a primary means of isolation in commercial retrofit work.
How is the ballast removed during a retrofit?
Remove lamps and the raceway cover, then identify the supply conductors and ballast leads. Disconnect or cut the ballast leads as close to the ballast as practical, remove the ballast mounting hardware, and clear the compartment for re-termination of the remaining conductors according to the LED tube wiring diagram.
Why does tombstone socket type matter in a ballast bypass retrofit?
Tombstone lampholders can be shunted or non-shunted, and the internal contact design determines whether line and neutral can be terminated safely at the same end of the lamp. Using the wrong lampholder type for the tube wiring method can create a short circuit or energize unintended parts of the fixture.
How is wiring handled for single-ended Type B LED tubes?
Single-ended Type B tubes take both line and neutral at the same end of the lamp, with one conductor landing on each pin. This requires non-shunted lampholders on the powered end so the two pins remain electrically isolated. The opposite end of the lamp is typically unpowered and functions as mechanical support only, per the tube manufacturer’s instructions.
How is wiring handled for double-ended Type B LED tubes?
Double-ended Type B tubes supply line to one end of the lamp and neutral to the opposite end. In many fixtures this can work with shunted lampholders, but compatibility is determined by the tube’s installation instructions and the existing fixture wiring topology. Each lampholder end should be wired so that pins receive the intended conductor without cross-connection.
What connections must be checked before reassembling the fixture?
Verify that all splices are made with approved connectors, conductors are fully inserted and mechanically secure, insulation is intact, and no bare copper is exposed outside the connector body. Confirm equipment grounding continuity to the fixture body and that lampholders are mounted securely with no cracked housings or loose terminals.
Why is labeling required after a ballast bypass retrofit?
After a direct-wire conversion, the fixture is no longer compatible with fluorescent lamps and may have line voltage present at lampholders in a way that differs from the original design. A retrofit warning label inside the fixture alerts future service personnel that the fixture has been modified for direct-wire LED operation and supports safer maintenance practices.
What should be verified during commissioning?
Restore power and confirm immediate lamp operation without flicker or intermittent shutdown. For commercial environments, confirm illuminance at the task plane using a light meter where required to ensure the retrofit meets the facility’s performance targets and applicable workplace lighting requirements.
Brandon Waldrop
As the lead technical specialist for our commercial lighting technical operations, Brandon Waldrop brings over 20 years of industry experience in product specification, outside sales, and industrial lighting applications.
His career began in physical lighting showrooms, where he focused on hands-on product performance and technical support. He later transitioned into commercial outside sales, working directly with architects, electrical contractors, and facility managers to translate complex lighting requirements into energy-efficient, code-compliant solutions.
Today, Brandon applies that industry experience to architect high-performance digital catalogs and technical content systems, helping commercial partners streamline the specification process and deploy lighting solutions with total technical confidence.