if i have a 400w digital ballast and i purchase a 250w hps because the 400w was too hot will the 400w ballast work on the 250w hps light?
It will most likely explode. You have to match the ballast to the bulb. If you didnt have to, there wouldnt be multiple ballasts in the first place.
i read that you can use a lower w bud with a higher w ballest but not a higher wat buld with a lower ballest.
You can use it if your ballast is dimmable to a lower wattage. I have a 600 watt Lumatek ballast that works with 400 and 600 watt bulbs. Is the heat an issue because you're growing in a very small space?
lumatek are the best balast made..i also have one but mine is a 400 running a 250..they are digital so they will run both bulbs.
a little trick i learned when i set up my cabinets...i use a cooltube with a 6" duct fan blowing air out my chiminey...put the intake inside the tent...it will pull alot of heat out of the cabinet as well as cool the light.