Technologies > PULSE-START METAL HALIDE

 

Description: Pulse-start metal halide (MH) lamps offer the advantages of standard (probe-start) MH lamps, but minimize the disadvantages. They produce higher light output both initially and over time, operate more efficiently, produce whiter light, and turn on and re-strike faster. Due to these characteristics, energy savings can be realized via one-to-one substitution of lower-wattage systems, or by taking advantage of higher light output and reducing the number of fixtures required in the space. Ceramic arc tube (CDM or CMH) pulse-start lamps can be specified for superior color performance and color control qualities in color-critical spaces such as atria, lobbies, retail, etc. When combined with an electronic pulse-start ballast, energy savings are increased.

Many retrofits of high-bay spaces currently involves fluorescent as a suitable candidate. Pulse-start MH systems are also a suitable candidate for these spaces. They are optimal in environments where ambient temperatures fluctuate or are extreme or in applications where facility professionals want to minimize lamp and fixture maintenance requirements. For retail environments, the sparkle of the HID point source is often preferred to the more muted appearance cast by fluorescent lamps.

The footcandles per watt performance of pulse-start or ceramic MH with a high-performance dome and electronic ballast is very similar to T5HO or T8 with electronic ballasting and good reflectors, according to Stan Walerczyk, LC, Principal of Lighting Wizards. Because MH ballast pricing is declining, T8, T5HO and electronically ballasted pulse-start MH high-bays may cost nearly the same, he adds. Although some of the electronic dimming MH ballasts can cost significantly more, their flexibility and performance can often provide the best total solution in some applications.

Saving Energy: A pulse-start system produces marginal wattage savings versus a probe-start system, so why should pulse-start be considered a good cost-saving alternative? There are several ways to significantly to reduce energy costs by switching to pulse-start.

First, because pulse-start lamps produce higher light output initially and over time, fewer fixtures are required to achieve the desired maintained light level. As a result, it may be economical to design or redesign the lighting system for fewer fixtures.

Consider a 100,000-sq.ft. application with a 20-ft. fixture mounting height and a target maintained light level of 50 fc. In this application, 290 standard 400W MH fixtures would be needed. Or 208 pulse-start 400W fixtures could be used, with a 30 percent savings in capital and operating costs.

The second option is to choose the 320W pulse-start lamp, which produces about the same amount of light output as a standard 400W lamp. Using the same example, we could use 290 standard 400W MH fixtures or 290 pulse-start 320W fixtures, a savings of about 20 percent.

Table 1. Comparison of 400W probe-start MH system with 400W pulse-start systems. Energy savings can be realized by reducing fixture count due to higher light output, or one-to-one replacement using 320W pulse-start systems. Source: Advance.

	400W Probe-start MH	400W Pulse-start MH Magnetic Ballast	400 Pulse-start MH Electronic Ballast
No. Lamps	1	1	1
Service life	20,000 hours @ 10 hours/start	20,000 hours @ 10 hours/start	20,000 hours @ 10 hours/start
Initial lamp light output	36,000 lumens	42,000 lumens	42,000 lumens
Ballast	Probe-start magnetic	Pulse-start magnetic	Pulse-start electronic
Ballast factor	1.0	1.0	1.0
Initial system light output	36,000 lumens	42,000 lumens	42,000 lumens
Lamp watts	400W	400W	400W
System watts	458W	452W	425W
Relative system watts	100%	99%	93%
Initial system efficacy	79 lm/W	93 lm/W	99 lm/W
Mean lumens	23,500 lumens @ 40% of lamp life	32,800 lumens @ 40% of lamp life	36,000 lumens @ 40% of lamp life
Lumen maintenance	65%	78%	78%
Relative maintained light output	100%	139%	153%
Maintained system efficacy	51 lm/W	73 lm/W	85 lm/W
Color rendering	65 CRI	65 CRI (80-90+ with CMH lamp)	65 CRI (80-90+ with CMH lamp)
Starting Time	4 minutes	2 minutes	<1 minute
Re-strike Time	10 minutes	4 minutes	4 minutes
Color temperature	3000-4000K	3600-4000K (3000-4200K with CMH lamp)	3600-4000K (3000-4200K with CMH lamp)

Disadvantages: Pulse-start lamps cannot replace existing probe-start lamps without changing out the ballast to a compatible pulse-start ballast, meaning the ballast also must be changed out in a retrofit, presenting a higher initial cost. On the other hand, this can be viewed as an opportunity to specify a dimming electronic ballast and maximize energy savings and shorten the payback through scheduled dimming, daylight harvesting and occupancy-based dimming. If the ballast cost jeopardizes acceptance of the project, energy savings can still be realized by instead considering 360W energy-saving standard MH lamps on the existing ballast.

In some applications, fluorescent may offer quality advantages compared to point sources. MH lamps can be less comfortable to look at directly, which can disadvantage MH in applications where occupants must look up (such as in a gym, playing a sport such as volleyball). As point sources, the light of MH lamps can also be easily blocked by large moving objects, such as a forklift loading or unloading pallets in high warehouse racks.

See also:

Ceramic Metal Halide Lamps

HID Electronic Ballasts

Metal Halide Tracklights

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