Lamp Operation


All fluorescent ballasts and lamps are not alike. Each ballast must be designed to operate a particular type of fluorescent lamp.

T4, T5, T8, T10, T12


The T designation refers to the diameter of the glass envelope of the lamp in eighths of an inch. Thus a T8 lamp is one inch in diameter, a T12 lamp is one and one-half inches in diameter.

Lamp Bases:

The other consideration in lamp definition has to do with the method of termination. Miniature and medium bi-pins are used in preheat and rapid start lamps. A few instant start lamps are available with medium bi-pins that should not be used on rapid start circuits. Single pins are used for most T12 instant start lamps. Dual rated T8 lamps are an exception to this rule. Double recessed contacts are used for high output (HO) and very high output (VHO) rapid start lamps.

Single ended lamps (compact fluorescent) utilize several different base configurations usually containing a designation includes the letter G.

Ballast Lamp Mismatch:

If ballasts and lamp types are mismatched, poor or no performance will result. This may include starting problems as well as shortened lamp and/or ballast life (incidentally, mismatching may void safety listing and ballast or lamp warranty). Pre-heat, instant start and rapid start lamps have different electrical needs and the matching ballast is designed to supply those needs.

Disclaimer: This information is intended to be general in nature and is not complete regarding ballasts or lighting fixtures. You should consult a qualified electrical engineer for specific applications. See our Terms and Conditions of sale and our warranty which are controlling and supersede this data.