Ballasts: 6 of 21

Most T-12 lamps today are operated on Rapid Start ballast. Almost all new T8 installations are Instant Start ballasts.

In a Rapid Start ballast the electrodes (cathodes) at each end are heated by a 3-4 volt supply before the arc occurs across the length of the lamp. The electrodes are kept hot during lamp operation; this uses up a few watts.

In an Instant Start lamp the electrodes are not separately heated; this saves a few watts. Today 80% to 90% of T8 ballasts in the field are Instant Start ballasts.

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Summary: Use Instant Start ballasts except in situations
where lamps are frequently turned on and off.