Posted On 26 Sep, 1969 By admin On Blog
With some sign ballasts tipping the scales at almost 20 pounds, they look as different from household ballast as a Lincoln Navigator does next to a Cooper MINI. Inside however, they’re just ballasts.
By Eric Bobbitt
The ballast performs three main functions. To facilitate starting, the ballast provides controlled energy to properly heat the lamp filaments. To operate the lamp, the ballast delivers the proper voltage to start and maintain the arc. And third, once the lamp is lit, the ballast limits the flow of current to the value established to ensure proper lamp operation.
~~
There are some specific aspects of sign ballasts that bear mentioning. UL concerns, sign ballast selection and application and installation factors are discussed below.
UL Designations
Sign ballasts incorporate a number of symbols and notations on their label that are easily recognized. There may be markings on the label that are not self-explanatory, such as Class “P”, Type 2 and HL. These are United Laboratories (UL) designations that indicate that the ballast meets certain industry requirements.
For the past few years, sign ballasts have been equipped with UL class “P” thermal protection. Class “P” is a requirement of UL standard 2161. Ballasts labeled with class “P” use an internal device that disconnects the ballast from the supply line if the internal temperature of the ballast coils reaches 105 degrees centigrade. Once the ballast cools down, the device automatically resets and normal operation resumes. If ballast is thermal cycling (repeatedly turning on and off as it heats up), it is due to excessive heat. The trigger could be high voltage fluctuations, loose ballast mounting, ballast approaching end of life or other causes.
Sign ballasts are generally manufactured using “UL Type 2 Outdoor” cans. A Type 2 can has a special coating to resist rust. The Type 1 can, used for general lighting applications, does not. Type 2 cans may be used in plastic sign applications without putting the ballast in a separate metal enclosure. “Type 2” does not mean weatherproof, but they do provide some moisture resistance.
Another UL marking on many sign ballasts is “HL”. The HL notation means that the ballast has no sparking components exposed to the air and is suitable for use in hazardous locations. “HL” is a typical requirement in the petroleum industry. All sign ballasts manufactured by Universal Lighting Technologies are UL class “P”, Type 2 and HL listed.
Choosing the Correct Sign Ballast
Selecting the proper sign ballast for your plastic sign application should be a relatively easy task. The normal sign ballast is rated for 120-volt input and operates 800 mA high output (HO) T12 lamps. Sign ballasts also are available for slim-line lamps or other voltages such as 277, however the vast majority of the installations are 120 volt HO. Typically lamps are operated in series (six lamp ballasts are two three-lamp series circuits, in parallel). With series wiring, the lamps are part of the circuit, so if one lamp fails, none of the lamps on that circuit remain lit. In signs using multiple ballasts, adjacent lamps will often be operated by different ballasts to avoid a large dark spot should one lamp fail.
The variables used to select the proper ballast are the number of lamps being operated and the total lamp footage. For example, the Universal Lighting Technologies’ SignaÔ sign ballast 256-448-800 will operate any one-, two-, three- or four-lamp combination of T12 800 mA lamps covering 8 (minimum) to 16 feet (maximum) total lamp footage.
Economies of scale and application are important in selecting the proper sign ballast. Sign ballasts have wide application ranges that often overlap. For example, Universal Lighting offers five different ballasts that operate two four-foot lamps. However, the most economical choice is the SignaÔ sign ballast 256-248-800, which is rated for any one or two lamp combinations of T12 800 mA lamps with total lamp footage of 3 (minimum) to 8 feet (maximum) lamp coverage. As a general rule, the most economical choice is to select the ballast where the actual application matches the maximum limits of the ballast. A ballast for one or two-lamps is generally less expensive than a ballast for one-, two-, three- or four-lamps, and a ballast that operates up to 16 feet (maximum) is less expensive than one that operates up to 24 feet. Choose the closest match as long as you don’t exceed the published lamp footage range.
No Comments