Volume 16, Number 4
Aug 1992

Selecting Fluorescent Lamps for W Output

Control of W exposure in spaces illuminated with fluorescent lamps can be problematic, even when W filtration is used. When W filters are used, the use of a low-W lamp is desirable since it will further reduce W levels, will reduce the damage from accidental misuse of W filtration, and will extend the life of any W filters used. To increase the likelihood that a low-W lamp is actually installed, a "standard" fluorescent lamp with low-W (less than 2% or 75 IlW/lumen output) should be selected. This reduces the chance of confusion and substitution when a non-standard special lamp is specified. Further, the chosen lamp should be used throughout the building or institution, even in non-collection spaces.

Since lamp stocking and procurement can be hard to control, and since use of separate lamps in different parts of the same building will rarely occur, it is a good idea to only have one type of reasonably-priced lamp used in the building.

Common "standard" lamps usually include White (W) Warm White (WW), Deluxe Warm White (WWX), Cool White (CW), Deluxe Cool-White (CWX), Daylight (D), and other specialty lamps from General Electric, Philips (Westinghouse), and Sylvania.

Manufacturers' lamp data available is summarized in Table 1 for 4-foot fluorescent lamps from the three major lamp manufacturers supplying lamps in the US. Most of the lamps are conventional T-12 lamps, while some are the thinner T-8 lamps, the two are not interchangeable.

The table shows the Sylvania Warm White (WW) and Cool White (CW), and the General Electric Deluxe Warm White (WWX) lamps to be the lowest in total W output. These three lamps not only have the lowest total W output but are below the 75 IlW/lumen criterion often used to select light sources in museums, libraries and archives.

Please note that the "same" lamp from different manufacturers can vary greatly in W output. For example, the GE Cool White lamp has almost twice the W of the Sylvania Cool White lamp; the Philips Warm White lamp has much greater W than the Warm White lamps from GE and Sylvania, although their Ultralume has less W than the "equivalent" GE SPX lamps, and the Deluxe Warm White from GE is one of the lowest while the "same" lamp from Philips is the highest with almost four times the W output (!). Specific manufacturer data must be used to select lamps; lamp types cannot be switched between manufacturers if W output is a concern.

Note that sometimes more expensive lamps with a "better" spectrum, such as the GE "SP" lamps, may be substantially higher in W. Energy-saving lamps, such as "Econo-Watt" and 'Watt-Mizer," may tend to have a high W output and although they can be considered, it is not likely that they will be among the low W lamps.

LAMP PROCUREMENT. The institution should consider a procurement process where bidders submit W output (WA, WB, and WC) of lamps to be provided. Lamps should be selected for lowest W below a certain arbitrary maximum price point per lamp. The price point should be selected to at least include the Sylvania Warm White, Cool White and GE Deluxe Warm White lamps.

NEW DESIGNS. For lamps where recent data is not available, the design professional selecting the lamps should secure W output (watts emitted below 380 nm) and lumen output of lamps specified, and submit them for approval.

W sleeves or another form of W filtration should also be used in any collection areas, for further W removal and as backup against lamp substitution. The combined cost of the standard lamp and a W filter sleeve should be less than a custom low-W lamp.

CUSTOM LOW-W LAMPS. Where specific color temperature or color rendering is required for a particular display, the institution could then use a custom low-W lamp as available from Varilux, and others, where specific color characteristics can be specified, where lamp replacement can be controlled, and the cost premium will be on a limited number of lamps.

Author's note: We invite interested parties to send us information on any other lamps for inclusion in an updated version of this table. Please send the lamp name, and the manufacturer's printed information listing the "total watts radiated under 380 nm, " "total visible watts," and "total lumens." The lumens should be noted as either initial or design. An updated table will be offered for publication on a regular basis.

1. Total Visible Watts are net of any UV component.

2. Total Lumens is the "design lumens" from the Philips data, and 90% of the "initial lumens" in the Sylvania data.

3. Sylvania data sources: Engineering Bulletin 0-341 0689 Table 1 "Energy Emission of Selected 4-Foot Lamps in Arbitrary Color Bands in Watts"; Large Lamp Catalog (for lumen output).

4. GE data source: GE "Spectral Output in MilliwattslLumen and Watts" sheet, dated 11 August 1990.

5. Philips data sources: Figure 17, Guide to Fluorescent Lamps dated June 1988; Lamp Specification and Application Guide, dated