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SOX-E Economy Low Pressure Sodium |
The principle difference is the improved thermal insulation. Firstly, it employs an infra-red reflective coating with a slightly higher tin concentration, which increases the number of charge carriers in the film. This in turn improves its infrared reflectivity without impacting the visible light transmission. In addition, the thermal insulation at the U-bend end is improved. It is not practical to apply the infrared coating to the domed end of the outer jacket, so instead a metal heat-reflective disc was added at this point.
Consequently, if each of the former SOX lamps is equipped with the improved IR coating and end disc, less input power is required to bring the arc tube up to its optimum wall temperature of 260C. Since lamp voltage remains about the same, the lamp current must fall to bring about this decrease in wattage. Always, the low pressure sodium discharge is at its most efficient for the lowest possible current density in the discharge space. So naturally the reduced current in SOX-E lamps enables them to run more efficiently, and pose a good energy-saving alternative to standard SOX.
Despite the increased efficacy, the total lumen output of each physical lamp size is reduced on account of its much lower wattage rating. Thus re-lamping SOX to SOX-E results in a fall in light output. However this was felt to be acceptable since many installations had become over-lit when the higher flux SOX superseded SO and SOI types 20 years earlier.
| Manufacturer: | The General Electric Company of England PLC | |
| Lamp Power: | 26 Watts | |
| Lamp Current: | 0.61 Amps | |
| Lamp Voltage: | 79 Volts | |
| Cap Type: | BY22d | Mycalex Insulator |
| Bulb Finish: | Indium Tin Oxide | Soda-lime glass |
| Bulb Type: | Inner: TU-14 x 32 | Outer: T-50 |
| Overall Length: | 311 mm | 12¼ inches |
| Light Centre Length: | 180 mm | 7 inches |
| Arc Length: | ||
| Electrodes: | CCC-4 Black Tungsten | BCT emitter |
| Atmosphere: | Na | 99% Ne, 1% Ar | Outer: Hard Vacuum |
| Luminous Flux: | 4,030 lm (@ 100 hrs) | 3,900 lm (lighting design) |
| Luminous Efficacy: | 155.0 lm/W (@ 100 hrs) | 150.0 lm/W (lighting design) |
| Colour Temperature & CRI: | CCT: 1700K | CRI: Ra-44 |
| Chromaticity Co-ordinates: | CCx: 0.574 | CCy: 0.425 |
| Burning Position: | Horizontal ± 15° | |
| Rated Lifetime: | 10,000 hours | to 75% survival |
| Warm-up & Re-strike Time: | 15 minutes | Instantaneous |
| Factory: | Shaw, Oldham | England |
| Date of Manufacture: | 1985 | |
| Original & Present Value: | ||
