June 02, 13
High Bay Lighting Features & Strategies
- High Bay Lighting Features & Strategies
The authoritative Illuminating Engineering Society of North America (IESNA) designates high bay lighting as 25 feet or higher and low bay lighting as less than 25 feet, although these heights may vary by manufacturer. Sometimes a skeletal framework is erected to house the lamp fixture. However high bay lighting is defined, it is typically utilized in big box retail, industrial, manufacturing and warehouse spaces.
Beginning in the 1960s these large areas have been illuminated by high-intensity discharge (HID) lighting technologies and more specifically metal halide (MH) systems, owing to the very bright and clean light it emits with high quality color rendition. In the past they were favored over incandescent and fluorescent lamps because MH lamps produce more visible light per unit of energy (a higher luminous efficacy) consumed. MH lamps also feature a relatively long lifespan of ~20,000 hours. But they do not have dimming options; the color rendition can degrade or change after extended use and are not designed for frequent on-off cycling. Most importantly, light output and efficacy decline as the lamp is used, thus requiring periodic re-lamping to regain its initial rating.
A new generation of MH systems is known as pulse-start metal halide. Long used in low-wattage MH lamps, pulse-start technology is now available in higher wattages up to 1000W. Compared to its predecessor, pulse-start MH lamps produce higher light output, feature higher lumen maintenance, are 15% more energy efficient, emit a whiter light and recycle more quickly. Pulse-start lamps also perform better in environments subject to temperature extremes. Its main drawback concerns the fact that it cannot be used with standard magnetic ballasts, thus requiring compatible pulse-start ballast refitting.
In today’s quest for higher energy efficiency and sustainability, lamp manufacturers have rolled out specialized T-8 and T-5 HO (high output) fluorescent fixtures as alternatives to HID in indoor applications. These products can deliver the same performance as traditional HID lighting up to a height of 35 feet but with greater lamp efficacy and energy efficiency. These specialty lights utilize high-intensity fluorescent (HIF) fixtures with specifically designed reflective capabilities. With advances in amalgam technology – the combination of certain metals with mercury inside the lamp – HIF can now produce maximum output levels over a wide range of temperatures. HIF for high bay applications has several distinct advantages over traditional HID: lower energy consumption, lower lumen depreciation rates (thereby reducing periodic re-lamping), better dimming options, faster startup and restrike, better color rendition and less glare. Thus for many applications, HIF combines cost savings with superior performance over traditional HID.
A new low-cost strategy for high bay lighting has emerged in the form of high efficiency plasma (HEP) lamps. They use half the power and cost half as much as comparable ceramic MH lamps. These electrodeless lamps potentially have a very long life with lumen maintenance of 90% throughout life, stable color, dimmable to 20% and a fast turn-on/hot restrike capability.
These are the most conventional options for high bay lighting. Care should be taken to find the best technology for optimum results as each environment has its own specific requirements.