Hullo, IF YOU WANT TO SKIP THE STORY AND JUMP STRAIGHT TO THE QUESTIONS, THEY'RE AT THE END OF THIS SEGMENT. I got a set of 400W HPS ballasts for free and decided to veg under one of them with a 400W MH bulb. It worked beautifully for three weeks. The temperature ran a steady 85 humidity 60% ... the plants were loving it. It was closet grow-op paradise. Then it all came crashing down! First ... the bulb burnt out. Like I said, it only took three weeks (500 hours). Around the same time the ballast stopped working (as I had a set of HPS bulbs that came with the lights I was able to confirm this). I made a reasonable determination that the MH bulb burnt out because it was being used in a HPS ballast. So maybe my mishaps are helping to set some sort of precedent. Next, I've determined (after reading that MH bulbs run HOT HOT HOT) that since mine was keeping so cool ... it had to be because it was in the wrong ballast? Also, I think the ballast is cooked because it's not working. I'm no electrician, I'm a framer ... so uh, I can build something to take my mind off my worries. So I switched out the ballast and ran a 400W HPS bulb in it instead. The next morning when I checked in the temperature in the room was pushing 100. I put a small air conditioner right next to the plants and a few more fans, and when I got home from work the plants were almost dead and it was close to 45 degrees Celsius in there. Yikes. Took the HID lighting right out (and the AC). At this point my plants are not under direct light, but I have 2x T5s starting seedlings up on the shelf above and there's enough resonant light so that it's not dark. It's also cold in there now. Poor plants . Too lazy for pics so let me describe what it looks like: standard wardrobe closet grow. Plants on floor with HID light about 20" above them hanging from a custom bracket mounted on the wardrobe shelf. Shelf is 12" from top of wardrobe ... seedlings and clones sit on shelf under T5s which are mounted on ceiling. Seems straightforward enough. I am going to kill my cat The veg room was kinda scrapped together. Venting is okay ... (there is active exhaust + air filter). Remember these are warehouse lights so a cooling tube is out of the question because they're not set up that way. They're meant to hang and have a big shroud. Flower room is fine. Beautiful. Not even in use yet. It's another closet wardrobe. 400W HPS Hortilux with a bathroom fan extracting air right next to the light and blowing out through a filter. Secondary fan blowing directly onto the bulb. Passive air intake (starting with 4" in lower corner might cut hole bigger depending). Air tight room. Thanks for reading. So what I'm wondering is ... what can I do for veg light at this point? I am supposed to be buying a 400W Metal Halide ballast from a guy today ... for $30 with a bulb included is not bad. A few questions: 1. Can I put a 250 W MH bulb in a 400W MH ballast? Internet generally says yes to this, but, there are those naysayers. 2. Is 250 W going to get hot enough to turn the room into an El Salvadorian heat wave? The space is about 3' X 1.5' area ... and 4' of height, with the tallest plant reaching within 18" of the bulb. I'm going to mount a fan and have it blowing directly on the bulb. 3. Should I just buy compact fluorescent? Thanks for the advice!
do me a favor and take a picture of this fixture... i am a commercial electrician, and i can tell you how to wire it so that you can put the ballast outside of the tent *which will help with the heat issues* also if it is the type of fixture i think it is, you could drill a couple of 4-6" holes in the side of the shroud and basically make an air cooled reflector. being an electrician, ive got a few of these high bay fixtures laying around myself (thank god for remodels ^_^ ).. pictures help though.
Mor'nin OK so I took a few shots. The one with the light actually installed is my flower room, which is not in use yet, but has been tested and is well ventilated and properly cooled (I think). The Metal Halide light that I'm considering basically looks just like the light I currently have. The pic is from Kijiji. My poor plants Also, the veg room setup. As you can see, at one point in time I happily had a light hanging from the shelf. Are you telling me there is a way to house the ballast externally AND wire the socket so it can be brought farther away from the ballast? Let's say I was less than eager to totally remodel the veg room (*sigh ... again!) and wanted to hang a MH bulb right where I was previously hanging the entire fixture. If you could talk me through that I just might roll with 400W.
oops, and to clarify: The reason why I had the light hanging in the first place is because the shelf is being used for clones and seedlings. There are 2x T5 mounted on ceiling. The resonant light from those are basically the only light the plants are getting currently.