The lowest cost ballast option may not always be the most practical. Using sign ballasts that operate many applications can simplify inventory needs and reduce costs. As long as the actual application is within the ballast’s published range, you can be confident with its performance. If the lamp application is listed on the ballast label, then it has met and passed all of the UL testing requirements.

Do not experiment by using a ballast that you happen to have in stock in an application slightly outside of the performance range. The sign could perform fine in the shop, however you’re asking for trouble in the field. Using a non-listed combination of lamps will void the UL coverage. Ballast overheating, excessive lamp end blackening, hard starting, short lamp life or short ballast life are a few of the possible field problems caused by using a ballast that is not rated for the application. Typical service calls for a plastic sign cost several hundred dollars. Saving a few dollars by using a “close enough” ballast is not wise in the long run.

Application and Installation Factors
Temperature has a critical impact on the performance of a sign. Light output is a factor of the mercury vapor pressure inside the bulb. The colder the lamp is, the lower the light output. Cold lamps are also more difficult to start. Magnetic sign ballasts are rated for reliable starting down to minus 20 degrees Fahrenheit. At temperatures below that, it can be difficult to start the lamps.

Another factor that can cause erratic starting is a poor ground. More importantly, grounding provides added safety. Sign ballasts are designed under UL standards for protection from shock hazard, however certain conditions of ballast failure at end-of-life can result in shorts. An ungrounded sign is a potential hazard and can give misleading symptoms when looking for sign faults. Always disconnect the power before servicing a sign. Service work should only be performed by qualified personnel and in compliance with OSHA guidelines for safe electrical practices.

The two main enemies of the ballast are heat and moisture. The ballast will generate heat during operation and by design should not exceed 90 degrees centigrade at the hottest spot on the ballast case. Higher operating temperatures will shorten the ballast life and could result in thermal cycling. To maintain normal operating temperatures, the ballast should be mounted against a flat surface of heavy gauge metal, such as a structural part of the sign, and it should be mounted far away from other sources of heat, such as other ballasts and lamps. A lamp will generate about three-fourths of the heat in a plastic sign. The ends of the lamp are the hottest part, so the ballast should be mounted as far away from the lamp ends as possible. To help reduce moisture the sign should be well vented without allowing water to enter.

High or low line voltage can have a major impact on the life of the sign components. Low voltage does not generally impact a ballast life, yet it can result in inadequate filament heating during starting, shortening lamp life. High line voltage can result in shortened life for both the ballast and the lamps. It is recommended that corrective measures be taken if the voltage is less than 110 or higher than 125 on a nominal 120 volt circuit.

That’s a quick thumbnail sketch of what a sign ballast is, and some application issues that might arise. It is important to recognize that the sign industry and its governing body are anything but static. Restrictions on the size of signs are commonplace and limits on energy consumption are starting to be enacted. Overall, the industry is changing with the times. Over the last few years, there has been a shift in product mix towards the smaller ratings and an increased interest in the use of alternative lamps, such as the T8 high output. Electronic sign ballasts also are growing in popularity. These developing products show a great deal of promise and will become more important as our industry and the application installation challenges continue to evolve.

Editor’s note:

Mr. Bobbitt is Vice President of Sign and Neon Products, Universal Lighting Technologies Inc. Please forward all reader inquiries to:

Universal Lighting Technologies Inc. Marketing Communications Manager 26 Century Blvd. Suite 500 Nashville, Tenn. 37214-3683 1-800-BALLAST www.universalballast.com webmaster@universalballast.com