Hi,
The 500W halogen light on my drive has just failed for the nth time.
I'd like to save some energy and lamp costs by replacing with a sodium light of some kind (ideally with a dusk sensor), and on a timer.
Problem is that all the sodium lights I can find are ugly, looking more appropriate to prison perimeter security or perhaps use on offshore oil installations.
Example:
David
You can buy 18W SOX luminaries from your local electrical wholesaler that will be more than adequate for lighting the average domestic drive. They look not dissimilar to square bulkhead lights, but mounted horizontally, with the glass facing down. Personally, I prefer 2 x 9W or 4 x 9W low energy floodlamps, which have shorter start-up times.
Colin Bignell
A little better:
You could use a luminare (fitting) for an ordinary lamp, and mount the control gear remotely. The easiest way to get all the bits is probably to buy a luminare like the one you identified, and then butcher it for parts. If you go this route, keep the cable between the control gear and the lamp as short as possible, and beware high voltage pulses are used to start these lamps (long cable dulls the high voltage pulse and can cause RFI). Go for a luminare rated in excess of the power consumption of the lamp (at least 100W, and preferably 150W) as the sodium lamp will prefer running a bit cooler than a filament lamp. Any reflectors in the luminare for use with high pressure discharge lamps must be of the specular type (as shown in that Screwfix picture), and not plain polished which can cause arc tubes to overheat if it reflects the heat back onto them (which is the exact opposite of what you ideally want for a halogen lamp).
Oh, and these lamps are only suitable for timed and/or dusk to dawn operation, not PIR (movement) sensors.
SOX (low pressure sodium) have a particularly long run-up time, typically 9 minutes for the larger sizes (never played with the low power ones, but might be a bit faster because they aren't as efficient). SON (high pressure sodium) are significantly faster at around 2 minutes (just measured a 250W one -- 70W is probably not much different).
Neither is any use if you want instant-on, hence my comment about PIR usage.
What about the colour of the light?
SON is much more appealing (or should I say less unappealing) because it has a better colour spectrum. See
David
SOX is just the two yellow sodium lines, so there's virtually no colour discernable.
SON is a peachy colour (a sort of very warm white). The colour is built up up from broadened sodium lines due to high pressure operation, mixed with mercury lines which is also present in the arc tube.
Another option is metal halide, which is white, commonly available as warm white (2700K) suitable for nighttime use, and higher colour temperatures (4000-5000K) for supplementing daytime light in shop displays.
Efficiency of these three lamps runs in opposite direction, with SOX the most efficient (although the small ones less so), and metal halide least efficient.
Probably about the same. I have them outside my factories.
I've never measured them, but you are probably right. I use them as high bay lights inside one factory, with HF fluorescents on the same circuits to provide some instant light at switch-on.
The OP's suggestion of a dusk sensor and timer suggests that instant-on is not important.
Colin Bignell
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