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Can you replace a 250 watt lamp with a lower wattage lamp without changing to a lower wattage ballast
 

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:blink:

You must not understand the question.
Maybe, but I have changed many 400 watt lamps to 300, or so watts. I have also changed 400 watt lamps to 250 without a problem that was reported. To me a ballast is just a transformer that will supply what is required up to its rated wattage and then start heating up. To have it supply a lower wattage would seem to make it run cooler. Am I misunderstanding?
 

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Maybe, but I have changed many 400 watt lamps to 300, or so watts. I have also changed 400 watt lamps to 250 without a problem that was reported. To me a ballast is just a transformer that will supply what is required up to its rated wattage and then start heating up. To have it supply a lower wattage would seem to make it run cooler. Am I misunderstanding?
The ballast also limits the current to the lamp.
 

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To me a ballast is just a transformer that will supply what is required up to its rated wattage and then start heating up. To have it supply a lower wattage would seem to make it run cooler. Am I misunderstanding?
A ballast is a current limiter, and is made to match the lamp.

Using undersized lamps will mean the ballast will supply to much current to the lamp possibly leading to an glass shattering failure.

Now, there are some energy saving lamps like 320 watts that can be used in 400 watt fixtures but the lamps are designed for that and the ANSI codes match


Click this link for more info about ANSI codes http://www.kolmart.com/HID-ANSI-Code-Guide_b_3.html
 

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Yes, the glass would most likely explode in a million pieces sending chards of razor sharp glass into someones cornea
That is a common failure when the lamp is at it's "end of life", or the fixture is rated for one type of lamp and someone installs another type.
 
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