250 MH / 400 HPS installed in the same reflector - distance question.

Discussion in 'First Time Marijuana Growers' started by wunschshrek, Apr 20, 2006.

  1. Hello everyone,

    My first grow is about 18 days old, and up until now they have been growing with a 250 watt MH light. Tomorrow (april 20th haha) my 400 watt HPS bulb and ballast is going to be delivered.

    I am installing them both in the same reflector, on opposite sides (MH in the top left, HPS in the bottom right)


    So it is a total of 650 watts.

    How far away would you have the lights from my plants? There are three plants and are roughly 20 days old.

    Secondly, out of curiosity, how much more heat can I expect from this new setup in comparison to now with just the 250 watt MH (which does not give off much heat IMO). The reason I ask is because this grow is being done in my walk in closet in my room, and I currently leave the door open so the plants can get plenty of C02, and I don't want it to heat up my room to much as I like it nice and cool myself, can't stand a hot room. If it gets to hot for me to be comfortable I have the option of closing the closet door, there is a AC duct in the ceiling and 16' fan which should take care of the heat, the only concern I have is not enough CO2 for the plants with my closet door closed.

    Thanks again,
    Sorry for rambling im sure I made my questions much longer then they should be haha.
  2. that reflector is going to be HOT. I would keep it off your plants by about 24". Rule of thumb is to put your hand under it at the level of your plants and if after 60 seconds, your hand is too hot, then it's too hot for your plants.

    I would recommend venting your hood and hooking up some ducting and a Vortex fan to it to suck the heat right out and into the attic.
  3. Hello and thanks for your comments up4anything,

    I will see what happens tomorrow, I am pretty confident I could install a vent coming off the top of my reflector with a exhaust fan if needed. I would just like to add though that there is a central air duct in the ceiling pumping out 65 degree air, and I bought a air coniditioner that I put in my room (the plants are in my closet about 15 feet away from the AC, but I keep my room door closed and closet open), and I have that set on 62. With the 250 MH I have now I can literally keep it two inches above the plants because thats how cool its staying, even the reflector is currently almost cool to the touch (however i once lighlty brushed my skin up against the bulb, youch!).

    So yeah hopefully it doesnt get to bad because I really hate being hot, especially when im sleeping :mad: Last thing I want to do is start sweating and shit just sitting in my room lol.

    Thanks again for your input and for listening to me ramble, I will use your hand test method and find the right length for me.
  4. yeah, you can cool all you want, but it's way more efficient to exhaust the hot air directly out of the reflector's hood - this will take the load off the A/C and help out the power bill quite a bit.
  5. Hi! Here's my situation, it may give you some idea what to expect...

    I have a 400wMH + 600wHPS combo light - Both lamps are under 1 reflector hood. The reflector hood has 4" holes, and I have a 265cfm squirrel cage fan connected to the hood with vent hoses cooling the light. The hot air is vented out the other side of the hood through another duct hose then vented outside the room. Room size is a 3.5' x 3.5' x 6.5' closet in my nice cool air conditioned basement.

    Currently I can only the run the 400w MH light in the room with the door closed. Temp stays around 78.4 degrees 29% humidity. If I turn on the 600w HPS + 400w MH lamp the temp starts rising by about 4 degrees an hour. The HPS runs signifigantly hotter than the MH. Even by itself, the HPS cannot be used with the door closed.

    An air conditioner will prob work to keep your heat down, but man your electricity bill is gonna be astronomical. Just running the two lamps at the same time will prob make your current bill almost double. Sorry about the long post, but I hope it helps.

    Cheers - HippyChic
  6. Thanks for the reply up4anything and hippychic,

    Well I got everything installed and it has been on for an hour now. I have it about 8 inches above my tallest plant, I can keep my hand about 4 inches away from the bulb and even there it is not really to hot for my hand, but im playing it safe and just going to keep it around 8 inches away and I am watching them very close for anything negative.

    Thanks again, I am going to start a grow journal now tomorrow for these three plants :hello:

    With the orange light, it appears I have a slight spider mite / white fly problem. I saw one or two flying tiny white bugs since the first day, but I never saw any damage until now with the orange glow it makes it stand out. I am going to spray the plant now with a mixture of soap, garlic, clove and red pepper I saw in another post. Atleast I caught it pretty early as it is only on 4 or 5 leaves out of all three of my plants, probably the size of a nickel all together from all three plants worth of damage.

    Best wishes and happy growing!
  7. id personally say to use the mh until your done with the veg stage,,,, and then put it away,,, and use only the hps light,,,,, you are overkilling here,,,,, that 400 hps will do you wonders without the excess heat from that 250,,, if shading is a problem down the road,,,then supplement your light with the 250... i will supplement mine with my flouros when im in between germination stages,,,they are on now at angles to reduce my shady spots,,just my 2 cents:hello:
  8. Thats allright I will use both, thanks for your input though. Heat currently isnt an issue, the central air and AC is keeping it cooled to 75 in my cloest, and im being generous with 8 inches above as even 3 inches away with my hand felt fine.

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