Help-600 MH to 315W CMH-burn out two of them

I’ve replaced a 600W MH with a 315WCMH twice now and both times the bulb burned out in a second.
I didn’t change the wattage, just kept ballast set at 600…
Should I set the ballast for 400W. My ballasts won’t go any lower than 400.
What should I do? Can’t afford burning out bulbs at $60 a pop.

The ballast has to match the bulb. Not just the wattage but also the type of bulb. Look at the bulb manufacturer’s website to find the right ballast. Also look at the ballast manufacturer to see the bulbs it can run.


You can’t run a CMH in MH ballast a CMH draws 345w at start up than drops to 315 even at 400w you are running nearly 125% also CMH have a different start arc than either MH/HPS (need a proper ballast) buy a 400w HPS/MH bulb or get right ballast otherwise kill 315’s everytime even if you get it to start wouldn’t last


Doh, that really sucks. The others have you set, match ballast with bulb.

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They do make MH bulbs that work with an HPS ballast, which is good if you go old school and run MH and then HPS for flower. You just need the standard magnetic HPS ballast. But you have to buy the right kind of MH bulb for that. I think it’s called a “retrofit bulb”. Most MH bulbs need their own ballast.

I assume CMH is yet a different ballast, that only works with CMH. What ever you do buy, the ballast types and wattage have to match or else POOF!