Mercury vapor lamps have been used for decades to provide high intensity lighting in industrial, commercial and street lighting applications. Over time, the magnetic ballasts that operate these lamps can fail or wear out. Replacing the old magnetic ballasts with newer, more energy efficient electronic ballasts can save energy and extend the service life of older mercury vapor fixtures.
Reasons for Replacing Mercury Vapor Ballasts
There are several reasons you may need to replace a mercury vapor lamp ballast:
- The ballast has failed completely and the lamp will not start. Older magnetic ballasts can simply wear out over time.
- The lamp flickers, does not reach full brightness, or cycles on and off. This indicates the ballast is failing.
- You want to upgrade to a more energy efficient electronic ballast. Electronic models can save 20-30% in energy usage.
- The lighting system is being upgraded and you need to match new ballasts to the existing lamps.
Replacing bad magnetic ballasts with new electronic ballasts can extend the service life of older mercury vapor fixtures and save on energy costs.
Ballast Compatibility Considerations
When replacing a mercury vapor lamp ballast, you need to select a new ballast that is compatible with the existing lamps. Key factors to consider are:
- Lamp wattage - Match the new ballast to the wattage of the installed lamps. Using a ballast with a higher wattage rating than the lamps can result in premature lamp failure.
- Lamp type - Mercury vapor lamp types include clear, phosphor-coated, self-ballasted, and subminiature lamps. Choose a ballast designed for your specific mercury vapor lamp type.
- Number of lamps - Make sure the new ballast is rated for the number of lamps it will operate. Many mercury vapor fixtures have multiple lamps per ballast.
- Input voltage - Select a replacement ballast designed for your input voltage (120, 208, 240, 277, 480 VAC, etc).
- Dimming - If dimming capability is needed, select a dimmable electronic ballast. Magnetic models do not allow dimming.
Always review the lamp-ballast compatibility specifications before selecting a replacement ballast. The ballast must match the lamps for proper and safe operation.
How to Replace Mercury Vapor Ballasts
Replacing a mercury vapor fixture's magnetic ballast with a new electronic ballast is a relatively straightforward process:
Turn Off Power
- Locate the circuit breaker or fuse powering the mercury vapor fixture and switch it to the OFF position. Use a multimeter to verify power is OFF before proceeding.
Access the Old Ballast
- Remove the fixture's lens, hood, or enclosure to access the lamp sockets and ballast. In some fixtures the ballast is mounted externally.
- Label all lamp socket wires to identify their connections.
- Disconnect the input power wires to the ballast. Often these are labeled LINE and LOAD.
- Disconnect all lamp socket wires from the old magnetic ballast.
Install the New Electronic Ballast
- Mount the new electronic ballast in place of the old one. It may require new mounting holes.
- Connect the ballast input wires to the incoming LINE and LOAD wires.
- Connect the lamp socket wires to the corresponding ballast output wires.
- Ensure all connections are secure. Use wire nuts or terminal blocks as needed.
Restore Power and Test Operation
- Restore power at the circuit breaker or fuse.
- Verify proper lamp operation. Electronic ballasts operate lamps at higher frequencies which may produce audible noise.
- Reinstall the fixture covers once operation is verified.
With the correct ballast matched to the lamps, the mercury vapor fixture should now operate efficiently with the new electronic ballast. Proper lamp-ballast compatibility helps ensure optimal light output and service life.
Benefits of Electronic Ballasts
Upgrading from magnetic to electronic ballasts for mercury vapor lighting provides several benefits:
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Increased energy efficiency - Electronic ballasts can reduce energy usage by 20-30% compared to old magnetic models. This provides ongoing savings in electricity costs.
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Longer lamp life - Electronic ballasts operate lamps at higher frequencies which optimizes lamp performance and extends service life.
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Faster start times - Electronic ballasts start lamps more quickly, reaching full brightness faster than magnetic ballasts.
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Ballast life - Electronic models typically last 50,000 hours compared to just 20,000 hours for many magnetic ballasts.
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Ballast noise - Electronic ballasts generally produce less audible humming or buzzing noise.
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Dimming - With a compatible dimmable ballast, light levels can be adjusted. This allows tuning lighting for changing needs.
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Safety - Electronic ballasts avoid the heavy use of wires in magnetic models, improving electrical safety.
While requiring a higher initial investment, new electronic ballasts save energy and operating costs over time while optimizing lamp performance in aging mercury vapor fixtures.
In summary, with some electrical safety precautions and matching the proper ballast to the lamp specifications, DIYers can successfully replace mercury vapor ballasts and breathe new life into older fixtures. Choosing electronic over magnetic provides efficiency and performance advantages. The result is upgraded lighting at lower long term cost.