I picked up a sunsystem 250w HPS lamp yesterday for $75 on craigslist. It's one of these ballas/reflector combo lamps. It works great but when I get it down close to my plants, say 12 inches from the top of the soil, the temp reading right at the top of the soil goes to 95 degrees. Is this pretty normal or should I be looking to move the lamp back further? I had it 3 or 4 feet up over night last night and temps were mid 80s. To get an idea of how the temps change further from the light I put the thermometer on the floor and got 89 degrees, so 95 at soil level with light 12 inches from dirt, and 88 on the floor, which is about 10 inches lower than the soil. I can't air cool this hood without some extensive work, it has no vents on top to put a flange in. It also has no glass, but it does have rails to slide glass into. Any thoughts? If this is normal with a HID lamp then I'll just let it ride like this. When the plants are taller it would only be the very top that is in that kind of heat. I'm sure everyone deals with this problem....I'd just like to know the best way to handle it. Thanks!
Sounds like you need fan blowing across the light. Even with an enclosed reflector I have fans blowing across. If it was ME I would buy this http://www.walmart.com/catalog/product.do?product_id=9219112 and suspend it level with the hood.
I can buy glass for the reflector, would that help contain the heat? It does't seem reasonable to me to slide the glass piece in with no exhaust of the heat. Would that be bad for the ballast/bulb?
I wouldn't seal it off without some type of exhaust like you have stated. Granted these lights run on the street enclosed, I just do not know enough about your system. I understand they make lamps but I didn't know they had hoods,sockets, and ballasts. All I can really say is 95 is TOO hot, hopefully someone else will chime in with experience. Define extensive work ? Maybe you can rig up some ventilation through the hood after adding a glass...
Well it's sheet metal. You have me thinking now I'd need to cut a hole in the end of the hood and add a flange of some type to add an exuast tube. I could also just add a 12v PC fan to the inside of the reflector exhausting air out while the light is on. I suppose a combination fan/flange would be appropriate as well. Mostly is the cutting and drilling of the sheet metal reflector housing that's "extensive" because I don't have the tools required to do it. Here's a pic of the light I have : http://www.midwesthydroponics.com/products/images/lamps_lights/cat_6.jpg
I cut the hood and installed a 12v 92mm server fan blowing outward. I'll get the glass for it if I need to and I think I can get a 3" ducting flange that I could screw to the outside to add a 3" exhaust line if needed. Hopefully what I've already done is good enough. Here's to cooler temps: