HPS light fixture

[JdoubleU]

I had a problem with a out side light pole that was blinking on and off every 20 seconds or so. The ballast said that the lamp should be a high pressure sodium 70watt. The owner had put in a 35watt lamp. I put the 70 in and it worked fine. Why can't the fixture take a lower wattage?

 

[charlie]

. . . Why can't the fixture take a lower wattage?

I am a long way from a knowledgeable person about this subject but, I believe, the ballasts are designed for the lamp and they will not work well with different lamps than what they were designed for. You have raised and interesting question.

 

[nakulak]

I believe that the ballast was overheating, the thermal cutout was turning it off, (repeat)

 

[iwire]

I had a problem with a out side light pole that was blinking on and off every 20 seconds or so. The ballast said that the lamp should be a high pressure sodium 70watt. The owner had put in a 35watt lamp. I put the 70 in and it worked fine. Why can't the fixture take a lower wattage?

The job of the ballast is to limit the current that can be supplied to the lamp. A 70 watt ballast will allow to much current to flow into the 35 watt lamp. The 35 watt lamp will run bright and as mentioned by nakulak it will run hot and cycle off and on.

 

[JdoubleU]

Thank you. That makes since