Using State-of-the-Art Screw-Based Lamps

Oct 1, 2007 12:00 PM, By James R. Benya, P.E., FIES, FIALD, LC, Benya Lighting Design

How to overcome obstacles encountered in retail and commercial lighting environments

The cost of high-technology lighting is widely acknowledged as a barrier to the greater use of advanced sources in retail and other commercial lighting applications. Compared to the first cost of basic halogen display lighting, state-of-the-art metal-halide (M-H) and fluorescent lighting systems can increase initial costs by 300% to 500% with payback periods often exceeding five years.

For feature displays and special items, such as jewelry, the objective is to raise the light level on merchandise to about 200 footcandles or more. As long as the object is not too large — or the distance is not too great — the 25-watt ceramic M-H lamp can meet many of these retail display lighting requirements.

Meanwhile, there are a lot of stores out there where track lighting is the only option. Offering an inexpensive and flexible design approach, track and track fixtures have been popular for decades, especially when energy was cheap (prompting many store owners to fill their tracks with PAR-38 and R-40 incandescent flood lamps). But with a ceramic M-H track light with integral ballast costing more than $200, the low-cost track option was just about wiped out.

It would seem that a practical solution to the problem would be some sort of self-ballasted lamp that could be screwed into existing track lighting systems. After all, compact fluorescent lamps (CFLs) with integral ballasts and medium screw bases are a well-established concept for residential and hospitality lighting — but not so for general commercial and retail lighting (especially for directional and display lighting). CFLs lack the punch needed to create dramatic retail lighting — largely because screw-based products were developed for the residential market, and the lamp characteristics were optimized for this use. As a rule, most products today are low-cost, moderate efficacy consumer products that produce warm-toned blobs of light. Until now, retailers either had to pay the high price of lighting fixtures or the high price of energy to power these systems.

However, exciting new PAR-38 screw-based lamps have been introduced within the last year that you can install in low-cost track lighting systems, saving retailers about half of the energy normally used by standard halogen lighting systems. In fact, you can install a combination of self-ballasted ceramic M-H and CFLs in low-cost track luminaires for 60% to 65% less than regular HID and fluorescent track lighting equipment. Depending on electric utility rates, payback periods in most areas of the country can be quite a bit less than five years.

The self-ballasted HID lamp

In 2005, a revolutionary new product — the 25-watt, self-ballasted PAR-38 ceramic M-H lamp — was introduced. Its comparatively low cost of about $60 in moderate quantities makes a competent and efficient modern display luminaire out of ordinary, low-cost track or recessed lighting. Compared to a conventional M-H track system, this lamp creates a display lighting system for less than half the cost.

For general display lighting, the objective is to raise the light level on merchandise to about 30 to 50 footcandles above the ambient light level. For special displays, 70 to 100 footcandles are needed. For feature displays and special items such as jewelry, 200 footcandles or more are expected. Table 1 (click here to see Table 1) shows that the 25-watt ceramic M-H lamp can meet many of these retail display lighting requirements. In other words, the 25-watt lamp is a good option for retail and display lighting, including jewelry, as long as the object is not too large or the distance is not too great.

The problem with these lamps is that they are not really suited for general and ambient lighting. Unless being used for display, a softer and wider spread lamp is needed. Fortunately, the new PAR CFL lamp is a perfect mate.

The professional-grade PAR-38 self-ballasted CFL lamp

Rather than using an inexpensive reflector lamp, these “professional” lamps employ a PAR-38 aluminum reflector, which improves the appearance and the performance of the lamp, offering better heat dissipation for the internal ballast. Table 2 (click here to see Table 2) compares the performance of the ceramic M-H “wide flood” to the professional-grade PAR CFL and consumer-grade CFL.

While the M-H lamp is good for highlighting, the CFLs excel at ambient lighting, general lighting, wallwashing, and other lighting applications where a broad beam of light is desirable. Visually, the effect of either CFL is extremely similar to a 75-watt reflector lamp, with comparable candlepower and lumens. Between the two fluorescent options, the advantage of the professional lamp is efficiency; you're able to use about one-third fewer fixtures and fewer watts to achieve the same footcandle level. From a life-cycle cost standpoint, the less expensive reflector lamp will cost more than the PAR lamp in added energy, relamping, and fixture costs.

Fig. 1. Room (left) with general downlighting using 25-watt ceramic M-H lamps on track. Room (right) with general downlighting using 23-watt PAR CFLs lamps on track. Note that ceramic M-H lamps are not recommended for use in existing recessed lighting fixtures.

When used for general lighting, you can install all lamps on track in low-cost lampholders. Very comparable results occur: At about 1 watt per square foot, a relatively even ambient light of about 30 to 35 footcandles is achieved, which is suitable for many different uses. The rooms, however, look a lot different. The M-H lamps tend to create more pools and shadows while the CFLs produce a softer and more even wash (Fig. 1).

Fig. 2. Wallwashing (left) with track using 25-watt ceramic M-H lamps and wallwashing (right) with track using 23-watt PAR CFLs.

When used for wallwashing, the technical performance of the lamps is also very comparable. As rendered in Fig. 2, with track luminaires mounted about 30 inches from the wall and 4 feet on center, both lamps produce average light levels on the wall (not including ambient contribution) of about 20 footcandles, average in the critical area between +42 inches and the ceiling with uniformity of about 6:1 (max:min). But again, the visual appearance is much different. The M-H wash is striated and spotty while the compact fluorescent wash is smooth and even.

Given that the performance of the two lamps is technically similar in these two common uses, the CFL offers several key advantages over its ceramic M-H counterpart: significantly lower cost; smoother, more even effects; immediate start and restrike; choice of color temperature; and dimmable version of CFL available.

The complete solution

A good lighting design would generally use a combination of lamps — the CFLs provide fill light and washes, and the various ceramic M-H lamps provide feature/general display lighting. Major advantages of the mixture include lower first cost and having a majority of the system capable of coming right back on after a power “blip.”

What's important about this pairing is the ability to provide high-efficiency display and general lighting from ordinary track or consumer-grade can lights. Because both lamps offset 60-watt to 75-watt tungsten sources, you can literally screw in a responsible display lighting system operating at about one-third the original wattage to existing PAR-38 fixtures. Assuming a 50/50 mixture of CFLs and ceramic M-H lamps, the payback period could be as short as one year in 24/7 businesses, and less than two in those with more conventional hours. For energy code compliance, you can also use these products on track lighting systems with inline current limiters to achieve cost-effective retail lighting systems.

Benya is principal of Benya Lighting Design in West Linn, Ore.

Sidebar: Weighing Wattage

Can a self-ballasted ceramic metal-halide (M-H) lamp be made using a higher wattage lamp? After all, if the 20-watt ceramic M-H can out-perform 50-watt MR16 and even 60 watt HIR lamps, then a 40-watt ceramic M-H lamp could be used instead of 80-watt to 100-watt halogen lamps.

Unfortunately, the answer is probably not. The 25-watt lamp package allows the integral ballast to operate at sensible temperatures, but a higher wattage lamp and ballast will probably get too hot and fail prematurely. For the present time, the low-cost, self-ballasted M-H PAR lamp for all intents and purposes appears to be limited to 25 watts.

Sidebar: What About LEDs?

Some LED products have been promoted as an alternative to halogen display lamps. However, at present, there are no inexpensive LED products that perform well in comparison to the CDM and CFL lamps discussed here. Moreover, heat-related issues of LED lamps with present technology prevent a practical, PAR-38 LED with comparable lumen output and candlepower to either of these lamps.

For the foreseeable future, the only real competition to these PAR-38 lamps will be from fixtures with separate lamps and ballasts, but it will take some clever packaging and much lower component prices before they can compete economically with these screw-in based lamps. However, things are changing rapidly. Within the next year, a practical LED product may be introduced.