Traffic Signal and Street Light Information Sheets
Willis Lamm
1/6/14
  Preserving Historic
Street Lights

Concepts for improving the
efficiency of historic and
vintage street light systems

Part Three

  Retrofit
Field Trials

Please note: This feature is a continuation of a report that originates in Part One.

Finding a "friendlier" light.

While this was not an extensive trial, we did try a few alternatives to 175 watt mercury vapor bucket type illumination for area and private roadway lighting. The MV lamps were at least seven years old. As a result both their lumen output and CRI had declined. One of the buckets had been partially painted to reduce trespassing light.

The experiment involved replacing the MV luminaires with salvaged NEMA style pendant incandescent lamps to compare with the MV lamps being removed. The object was to produce a comparable level of safety and longevity with a more cost-efficient and pleasing light source.

The NEMA pendant lamps were outfitted with CMH and CFL lamps for dusk to dawn operation. The results were encouraging.

70 Watt CMH lamps provided a nearly incandescent quality light that was not harsh or annoying. CMH initial lumen output is less than the initial lumen output of the 175 watt MV lamps, however the higher CRI appeared to make the overall light produced more useful, as expected. CMH is clearly a practical option with incandescent lamps that will accept a retrofit kit.

CFL lamps provided the most surprising results. 68 watt lamps installed in NEMA pendants having rippled glass diffusing globes produced light similar to 4000 lumen series incandescent bulbs. The larger light-producing surface of the CFL produced a "smoother" light through a rippled glass globe.

68 Watt 4200 Lumen CFL in a repurposed Westinghouse AK-10 pendant lamp
Even distribution of light against the diffusing type globe

One interesting comparison involved comparing the performance of 68 Watt CFLs with 405 Watt incandescent lamps in GE Form 79 luminaires with 205 globes and Line Material Spherolites. (Both types are the classic "gumball" design.) Both types were placed in operation in the same area. While the 405 Watt incandescent lamps produced more light in terms of lumen output, they produced significantly more glare that as a practical matter interfered with the effectiveness of the light being produced. The much larger light producing surface of the CFL produced a relatively even illumination of the diffusing globe which in turn reduced glare and provided more uniform light distribution.

Globe removed, showing concentrated source of light - 405 watt incandescent lamp.

85 Watt 5500 lumen CFLs approached the usable output of a comparative 405 watt 6630 incandescent lamp. We didn't acquire a 105 watt 6900 lumen CFL to try as we didn't need that high of a light output, however it is reasonable that this screw-in retrofit would produce slightly greater initial light than the 405 watt incandescent and still be comparable at the end of its service life.

CFL installed in a modified series Line Material with Teardrop diffusing globe.

We did not observe any particular anomalies while using alternative light sources within diffusing type globes as they rely primarily on internal deflectors to reduce light output on the "house side" of the luminaire and otherwise tend to distribute light relatively evenly. Our observations led us to conclude that CFLs were well suited for luminaires that did not rely on refraction to direct as well as limit the output of light.

Refractor Globes

Refractor globe luminaires proved to be more challenging. Their refactor facets are designed to receive light from a more pinpoint source (an incandescent filament.) A full length spiral type CFL tended to produce glare similar to the 175 watt MV bucket unless the socket was readjusted deep into the luminaire head.

Same spiral CFL installed in a Line Material with Spherolite refracting globe.

The excessive glare problem associated with refracting globes was alleviated by going to a non-spiral CFL or shorter LED retrofit that limited the size, but also affected lumen output. The image above was taken of a lamp equipped with a 68 Watt CFL installed at 14 ft. elevation. The glare issue also tended to be reduced when the height of the luminaire was increased.

The most glare-free light output with respect to refractor type luminaires were produced by CMH retrofits as their light sources are more compact. CMH would most likely be the most desirable replacement for applications requiring greater than 4,000 lumens in refractor type luminaires.

Since NEMA luminaire components are interchangeable, we also could swap reflector-globe units to make the most efficient use of various light source / globe combinations based on the light distribution that we desired from each lamp.

Other Experiments

In the shop we experimented with a various retrofits in about a dozen vintage luminaires. We could generally find a retrofit for any purpose.

"Daylight" CFL in a GE Form 175 produced a more MV like color.
This turn of the century GE Form 6 with a Holophane "Wide Spread" dual prismatic
refractor actually produced better light with a CFL than with an original incandescent bulb.

Practical Considerations

Our "test environment" is the high desert. Summer temperatures can exceed 100 degrees (F) while winter lows can approach -20 degrees (F.) At certain times of year we can experience sustained high winds with occasional gusts approaching 80 MPH - strong enough to rip polycarbonate buckets off MV luminaires. While the retrofitted luminaires did not experience constant vibration from heavy traffic, they did have to perform through a range of harsh environmental conditions.

The retrofits are in their fourth year of continuous service without experiencing a failure. (They actually have proven more reliable than new LED luminaires installed nearby by DOT.) Nonetheless there were a few issues were revealed that warrant consideration.

When selecting a CFL, initial start-up illumination data is important. CFLs that had more "instant on" characteristics seemed to experience the least loss of light output during extremely cold weather. In fact the change in light output in those lamps was barely noticeable.

Conversely the CFLs that required a significant warm-up period to come to full brilliance suffered a noticeable loss of light output when temperatures fell below 20 degrees (F.) These CFLs were generally in the lower lumen range, installed in low level luminaires used for path lighting, and their reactions to low temperatures seemed to increase with the age of the lamp. Therefore for outdoor use in colder regions, understanding the temperature related operating characteristics of CFLs being considered is important.

With one luminaire we experienced the loosening of a large CFL during windstorms. This phenomenon was attributed to the age of the socket. It seems feasible that an older luminaire that experiences a great deal of traffic or wind vibration should have its socket inspected during a retrofit. We found that a dab of 3M automotive trim adhesive applied to the lamp thread produced sufficient adhesion to prevent vibration-caused loosening but the lamp could still later be removed for replacement or servicing.

We have recently started trying 1,600 and 3,000 lumen LEDs. Our initial experience has been good as they eliminated the cold weather dimming issues associated with the lower intensity CFLs and their CRI is nearly equal to that of the CFLs. The LEDs are available in both warm and cool color temperatures for either security or traffic use. This is the first year of the LED trial so comparative longevity can not yet be calculated. However, so far the LED experiment appears to be encouraging.

For lower output reflector lamps (< 2000 Lumens) outdoor rated A21 LEDs perform well.

Conclusions

As a public employee I retrofitted incandescent luminaires to HPS and CFL lighting to achieve lower cost-per-lumen service as far back as the early 1980s. While I don't claim to be an expert, based on actual successes and failures I can assert that a well conceived retrofit project can be undertaken at reasonable costs and produce long-term operational savings.

After experimenting with alternatives to luminaire replacement over the past few years, it is clear that there are many appropriate situations where retrofitting existing luminaires can be both low cost and energy saving means for extending the service life of infrastructure that citizens and ratepayers have already paid for.

The availability of affordable isolation transformers from such manufacturers as OV-20 Systems opens a whole new world for improving the efficiency and service lives of series circuits, potentially saving hundreds of thousands of dollars in underground circuit and luminaire replacement.

Companies such as Ray-Lite produce a wide range of glass and polycarbonate diffusing and refracting globes that will fit most vintage luminaires at reasonable prices, providing an opportunity to match a retrofit light source with an appropriate globe in order to produce the most usable light with minimum glare and annoyance.

The intent of this feature is not to discourage the installation of better lighting technology where it is needed and where funds are available. However with dwindling resources available to maintain incandescent systems, we need to be aware that affordable and functional alternatives exist. Many vintage systems were designed to provide lower intensity high CRI lighting, and those designs can be sustained.

The experiments described here were not extensive or completely conclusive, but they do illustrate that before an agency spends vast sums in stripping out and replacing entire lighting systems, some investigation may be justified in looking at affordable and functional alternatives, even if just to extend the lives of circuits and luminaires until a complete overhaul of streets and utilities is scheduled.

Colorado Boulevard Arroyo Overpass, Pasadena, CA.


Continue to Replacement Globe Interchange Information

Return to Part Two

Return to Part One


For more information on how series circuits work, please see
Understanding Series Street Light systems


SAFETY FIRST!

When restoring any electrical equipment please always focus on safety first. The information presented here is basic and for illustrative purposes only. Your equipment and installation conditions may warrant taking additional precautions. Therefore the material presented here is not intended to supersede the recommendations of a qualified electrician who is familiar with your specific project and environmental conditions.


If you have comments, see an error or think of something that should be added to this section, please
Email me.


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