high pressure sodium

Old 07-12-03, 08:21 PM
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high pressure sodium

What causes a high pressure sodium light to cycle on and off about every five minutes? Ballast, bulb, or transformer? Thanks.
Old 07-13-03, 06:57 AM
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Many have a thermal cutoff switch. Is it lamped properly? Has it been working before, or is this a new install? They may be sensitive to brownouts.
Old 07-13-03, 08:31 AM
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Could be a cut-out switch like Ron mentioned, or might just be a bad bulb. Ever seen a street light that is going bad, they cut on and off until they just burn out completely.
Old 07-13-03, 11:29 AM
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This is a typical end-of-life condition for an HPS lamp called "cycling". You can often observe this phenomenon in streetlights. Replace the bulb quickly when you see this happening, since you are placing undue stress on the ignitor, which is the capacitor-looking device near the socket. This device provides a high voltage pulse to establish the arc in the lamp. These too can fail over time, since they are only rated for a certain number of starts.
Your problem is most likely just the lamp, though. Be sure to replace it with one of identical wattage.

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