Florida House Aglow with Lighting Retrofit

Danny Parker is a principal research scientist and Lynn Schrum is a research assistant at FSEC.

However, the household had a lot of miscellaneous plug loads, including three TVs, two VCRs, six ceiling fans, a home computer system, electric clocks, a dishwasher, and a vacuum cleaner (see Phantoms Strike Miami). In order to keep these miscellaneous loads from distorting the data, we installed individual time-of-use light loggers or plug loggers on each of the lighting fixtures in the home to establish the actual on-time of each. This let us assess how monitoring pure lighting loads compared with calculating energy savings by subtraction.

We began light logger monitoring on August 8, 1995. We didn't have enough lighting loggers for all the lamps in the house, so we had to capture the pure lighting loads by metering two groups of fixtures at different times.

We inventoried the home's lighting, and found 40 lamps on 26 switches with a total connected load of 2.5 kW (see Table 1). In general, the lighting consisted of incandescent A-lamps of various wattages.

Researchers learned some lessons about placing loggers in enclosed fixtures. This logger continued to function, even after melting in an incandescent fixture.

Outdoor lights offer big potential savings, but pose problems for retrofitting and monitoring. These lamps were retrofitted using a motion sensor which provided some savings in the early evening. However, the residents usually overrode the control, and left the light on all night. To add to the problems, a dead moth on the photosensor disrupted the logging.

In Miami, the shortest day is 10.6 hours and the longest is 13.7 hours, a 23% difference in available daylight hours. We found greater loads during the month of December due to holiday lighting (see The Electric Bill That Stole Christmas). The residents took a ten day vacation in July, which combined with longer days to reduce lighting use in that month. Eliminating these exceptional months, the variation in use between June and November was 24%.

The connected household lighting load dropped from 2.5 to 1.1 kW--a reduction of 56%. In order to examine savings, we continued to log energy use for another six months.

Project installers were aided by the wide array of bulbs now available for retrofit purposes. This 5-inch triple tube 15W CFL worked well for several tight corners.

Converting the lighting fixture over the dining room table proved an insurmountable challenge. This is an attractive fixture that is used to illuminate the table's centerpiece. Its dimmer controls a low-voltage miniature 50W halogen PAR. This fixture is frequently left on for long periods of time--an average of 9.4 hours per day--and is seldom dimmed.

At first, we planned to provide a motion sensor control to turn off the fixture when no one was present. However, the switch wiring was in a solid concrete wall, making installation difficult, to say the least. We couldn't install a CFL in the fixture because the residents desired continuous dimming. CFL dimming ballasts that use conventional dimmers have since become available.

There was a second dining table in the Florida room, a glassed-in porch common in our state. The lamp over this table was less frequently used and proved easy to retrofit. We replaced its 60W incandescent globe with a 15W CFL globe.

In the monitoring, we encountered difficulties using the light loggers on outdoor fixtures. A significant number of false positives were recorded on exterior fixtures during the day. At first, we believed this could be avoided by using the logger's built-in sensitivity adjustment to dull the photometric element so that it operated only when the lights were on. However, the sun can be very bright--obviously brighter than the researchers' anticipations! Fortunately, we were able to correct our data--on days when the lights appeared to have gone off in the morning and back on at midday, we were fairly sure that the sun was interfering with the loggers. Another outdoor light logger became ineffective when a dying moth, attracted to the fixture at night, fell onto the photosensor.

We recommend other sensing methods, such as clip-on current transducers, for anyone attempting to monitor outdoor fixtures. Transducers do not depend on light to show whether a fixture is on or not; when it senses current passing through lamp wiring, it records that the light is on.

Deck the halls with CFLs...

We also learned about the danger of placing the loggers too close to lamps. By accident, we melted one of the loggers in the 180W incandescent kitchen drum fixture. Amazingly, the logger continued to take useful measurements for the entire period. Even so, such circumstances could create a fire hazard. 

The occupants responded positively to most of the changes. However, a CFL globe with a magnetic ballast was unacceptable for the Florida room dining table due to its annoying start up flicker. (This same lamp worked fine in the garage.) Similarly, the ten year old boy who frequently uses the second bathroom was at first surprised by the half second required for the electronically ballasted CFLs in the vanity lighting to start up. The mother preferred the retrofitted kitchen task lighting and saw no effective difference in the other fixtures. The father noticed no real change in lighting quality, in spite of his stated preference for a well-lit home (see They Like It, They'll Pay, and It Works).

The family was dissatisfied with the outdoor-lighting motion sensors until they realized that they could override the controls to keep the lights on. This proved to be a weak link in the overall retrofit. The new front-porch lighting was higher wattage than before, and the motion sensors were usually overridden during evening hours.

Similarly, the outdoor-lighting retrofit in the rear included a porch light with a motion sensor that was frequently overridden. The occupants left the light on from midnight until morning after the retrofit, although they hadn't always left it on before. The motion sensor retrofit saved little electricity except in the early evening hours.

Therefore, we recommend that retrofitters install CFLs or other more efficient lighting in outdoor fixtures rather than depending solely on motion sensor control. We could have obtained added savings of nearly 1 kWh per day by substituting two 15W CFLs for the two 60W incandescents lighting the front porch.

One place where motion sensors might have been appropriate was the den, but we did not install them there. The father frequently leaves table lamps on for many hours in the den with no one in the room.

We estimated savings from the retrofit in two ways. In the first method, we compared the metered lighting and plug loads from June 20 to December 10, 1995 (before the retrofit) with the loads from December 13, 1995 to June 20, 1996 (after the retrofit).

Figure 1. Average whole house lighting and miscellaneous energy demand before and after the retrofit. The subtractive method of determining savings assumes that the change is entirely caused by the lighting retrofit.

The second method we used for estimating energy savings was more traditional. We knew the wattage change for each fixture we retrofitted. We also knew the average daily use of each fixture, thanks to the lighting loggers. We multiplied the wattage change by the hours per day the fixture was on.

Unfortunately, the dead moth threw off the data for the outdoor rear fixtures only two days after the light logger was set up. As previously described, the motion sensor control of the front porch lighting was largely overridden and few savings were observed there. Thus, this method of estimating the savings did not account for any change in the outdoor lighting from the retrofit. Light logger data was not available for two altered fixtures due to a project oversight. Also, we logged most of the fixtures during summer and early fall, missing the high-use period in the middle of winter.

This method, therefore, gave us a very conservative estimate of lighting energy use. Nevertheless, it showed a 47%, or 5.2 kWh per day, reduction in lighting energy use, amounting to 1,900 kWh per year.

Depending on the estimation method, the simple payback on this retrofit was between two and three years, for a simple rate of return of about 40%.

However, it can be difficult for auditors to concentrate on heavily used lighting fixtures, since it's hard to know which fixtures are used more than two hours per day. This article was adapted from Danny Parker and Lynn Schrum, Results from a Comprehensive Lighting Retrofit, FSEC-CR-914-96, available from the Florida Solar Energy Center, 1679 Clearlake Road, Cocoa, FL 32922-5703. Tel:(407)638-1000.In our study the individual fixtures were metered, but most retrofitters will not have the benefit of such information for the homes they deal with. Fortunately, data from other studies provide insight into the typical hours that fixtures are used in various rooms.

The usage in our house was similar to the typical patterns found in the Tacoma study and other studies that preceded it. All of these emphasize the need to address outdoor lighting energy consumption. A simple rule of thumb, which our results bear out, is that all incandescent lights outdoors, in kitchens, and in living rooms are good candidates for replacement. Of course, circumstances differ in individual homes, and this should only be used as a guide to provide a better match to actual needs.

We sought the maximum possible savings, so we chose not to concentrate on high-use fixtures, but to install CFLs wherever they could fit. Had we followed the above advice (changing lighting only outdoors and in the kitchen and living room), we would have saved about 3.3 kWh per day, 30% of the household's lighting energy use, at a cost of only $168 for 11 CFLs. This strategy would have missed lucrative opportunities in the garage and den, but overall performance still would have been good--a $96 annual savings and a 1.7-year payback.

This article was adapted from Danny Parker and Lynn Schrum, Results from a Comprehensive Lighting Retrofit, FSEC-CR-914-96, available from the Florida Solar Energy Center, 1679 Clearlake Road, Cocoa, FL 329922-5703.
Tel: (407)638-1000.
 

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