Metal Halide Remote Ballast Configurations for High Temperature Environments|
Article - May 4, 2017 By LarsonElectronics.com
Metal Halide Remote Ballast Configurations for High Temperature Environments
According to a 2004 research paper conducted by the National Electrical Manufacturers Association (NEMA), most luminaries, including metal halide lamps, are designed and tested for environments with an average ambient temperature of 25°C. For hazardous locations with abnormally high ambient temperatures, such as oil and gas facilities, chemical plants and high-temperature laboratories, lights must be specially engineered to minimize risks associated with prolonged exposure to high heat.
For explosion proof metal halide lamps, this practice involves strategically installing the ballast away from the lamp – typically in a controlled location with lower temperature levels. Although modern metal halide ballasts are designed with active heat dissipating features, exposure to excessively high temperatures could easily decrease the lifespan of the lighting component. An increase in 10°C beyond the temperature threshold of the ballast could decrease its lifespan by roughly 50 percent.
Functions in Lamp Operation
To understand the importance of remote ballasts one must know the significance of the lighting component. During start up, metal halide ballasts regulate the proper starting current and voltage. Additionally, it limits the current to the lamp. Without this action, the lamp would destroy itself by drawing colossal amounts of current, resulting in premature failure (explosion).
In some cases, metal halide ballasts may serve as a transformer (inside the ballast) to meet the required voltage levels needed for lamp operation. For example, metal halide units that start up at 240 volts will need a step-up in voltage if the available voltage is too low (120V).
Due to the crucial features of metal halide ballasts, the NEC stresses the importance of overheating protection in the form of cutout devices. In the event of overheating, a switch cuts out power until the temperature normalizes. When the temperature decreases to normal levels, the device restores power, reactivating the ballast and lamp. This repetitive action is known as “cycling” and is also applicable to fluorescent luminaries (Class P ballasts – established by UL as a standard for indoor ballasts, with a case temperature threshold of 110°C for normal operating temperature of 90°C).
Advantages of Remote Ballasts
Installing metal halide ballasts away from other working components can help preserve lighting performance. By keeping temperatures cool, flickering and other abnormal functions are greatly reduced. Operators may also choose to remotely install metal halide ballasts to decrease sound disruption in locations that are sensitive to noise, such as movie sets and audio sampling facilities. For lighting installations in tight spaces, the ballast may be mounted in a different (spacious) location. This is also advantageous during maintenance, since it allows workers to trouble-shoot the lighting component with minimal disruption.
A reason why operators may choose to proactively monitor the ambient temperature of the ballast’s location is due to warranty disputes. It is common practice for manufacturers to offer specifications surrounding the maximum ambient temperature thresholds of ballasts. Exceeding this range, according to a report from the National Lighting Product Information Program (Volume 8 Number 1, May 2000), could potentially cause the warranty of the product to be void.
Not all hazardous work locations with high ambient temperatures require the use of remote ballasts. With proper cooling and ventilation, as well as consistent airflow surrounding the unit, businesses can avoid needing to separate the ballast away from the lamp. To know if your facility requires the application of remote ballasts, it is recommended to perform testing in the live environment prior to installation.