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3x3x8 400 or 600 Watts?

Discussion in 'Grow Room Design & Setup' started by HelloAll, Mar 2, 2013.


    HelloAll Member

    Hey guys,

    About to bite the bullet and place a pretty large and comprehensive order at greens.

    I'm swaying towards the Secret Jardin DR90. The dimensions are 90x90x180cm.

    Would you advise me to get a 400 watt bulb for this area, or 600? I can't really afford any more than a high powered 5 inch Ruck fan which pulls 365cm3 of air. Also will buy a simple Euro Reflector for these reasons 1. Cool tube loses some light. 2. Cool tube or a air cooled hood may overheat my fan as hot air is going directly to fan 3. Euro reflector has an open ended design so I assume are cooler than a closed hood system 4. Can adjust flaps to direct the light more efficiently to the grow area inside the tent.

    I don't want to buy another inline fan as I want to keep my order under £600 and I am already at approximately £550. I will buy an oscillating clip on fan as well.

    Also bare in mind I will be 'growing' in a 2x2" or 60x60cm area inside the tent, and in this space I will SOG 9 plants in 6.5 litre pots. As the light will be directly under the 2x2 tray and as the 400 watt bulb outputs 56,000 lumens this would provide 14,000 lumens per square foot to the tray if I direct the light well unless I am confusing things.

    Could anyone kindly advise me on whether I would easy handle a 600 watt bulb in that area or is it just a waste of electricity? The cost difference between 400 and 600 is negligible.

    In both cases I will be buying a dimmable ballast.

    To be honest I am leaning towards 400 watt. This is because 1. it seems to me that the 600 watt is overkill 2, the 600 watt ballast can only be dimmed to 360 while the 400 can be dimmed to 250 and therefore I have more ability to save electricity during veg period, and 4. more control over heat during the hot summer days as I could reduce to 250 watts.

    But reading these and other forums people swear by 600 and claim it produces far superior yields as well as being able to penetrate the canopy much better.

    Please help!

    The tent will go into a basement which has a small opening at street level which will allow fresh air into the room. I will vent straight up to the wooden floor boards on top the basement as as there are gaps in the wood and it would help heat the house as well. Any thoughts on this? Could rotting be an issue?

    mr2shim Well-Known Member

    Go with the 600w. I run a 400w in a much smaller area and if I could cool the 600w I'd be growing with it.

    HelloAll Member

    Thanks a lot for the reply mr2shim.

    What are your grow area dimensions and what temperatures do you usually experience inside the tent? Also what kind of locale do you reside it (hot, temperature, cold?).

    You really don't think the temperatures will be too high with the 600 watt bulb then?

    Also what is your grow medium, grow style (sog, scrog?) and average yields?

    Huge thanks again for your reply.

    nick88 Well-Known Member

    With a 2x2 area, the 400w is plenty light. The 600 will cause you more trouble with heat issues than the extra 200w would benefit. More is not always better
    knotmyself likes this.

    mr2shim Well-Known Member


    Usually 64-80

    It gets pretty cold here in the winter, bitterly cold actually. Summers are quite warm. Last year we were hitting 90's almost every day.

    You can check out my current grow or previous grow for more info. Current is in signature.


    If you're growing in a 2'x2' 400w is plenty. Your title says 3'x3' for that I'd say 600w

    budbro18 Well-Known Member

    Sorry to but in but id agree with mr2shim

    I run a 600 watt in a 4x4x6.5 grow tent and i can keep it pretty cool. temps outside are pretty low 20-40 but the tent stays a constant 65-75

    In the summer i use a window AC to cool over 1000 watts of lights and other things and i can stay fine with a low electricity bill.

    If you do get the 400 though i would recommend a metal coil HPS ballast and a CMH bulb

    Best bang for your 400 watts
    knotmyself likes this.

    neonknight420 Well-Known Member

    400W will be perfect.
    knotmyself likes this.

    knotmyself Member

    Have to agree, go with the 400, I just got a 600 and put it my 3x3x8 and Iv got to tell you heat is the issue now. Im having to leave doors open, fans blowing...and still around 90 in there... 600's put off a lot of heat bud. I wish I woulda thought about that before I got it. Good luck!

    budbro18 Well-Known Member

    get a 6 inch inline fan and the air wont have time to heat up haha

    thats what i use to keep mine cool and it does even with the ambient room temp being about 70
    209 Cali closet grower

    209 Cali closet grower Well-Known Member


    HelloAll Member

    Hey guys thanks all for pitching in. needless to say I'm still undecided.

    Yes I am getting a 3x3 tent but the tray and pots will be in the middle pf the tebt in a 2x2 area. so I will only need to illuminate a 2x2 area. The extra space is to give the ladies some breathing room.

    D can I expect to yield from a 400 watt bulb and a 600 watt bulb respectively,

    HelloAll Member

    Hey guys thanks all for pitching in. needless to say I'm still undecided.

    Yes I am getting a 3x3 tent but the tray and pots will be in the middle of the tent in a 2x2 area. so I will only need to illuminate a 2x2 area. The extra space is to give the ladies some breathing room.

    Does anyone have an idea what I can expect to yield from a 400 watt bulb and a 600 watt bulb respectively? Baring in mind that I am a novice and will be using organic soil and nutrients? Is 200g from the 400 watt a realistic and achievable target or will I be looking more at 100?

    budbro18 Well-Known Member

    Its easy to calculate how much youll get.

    take the # of watts and cut it in half.

    You can get that many grams if youre a newb. So thats kind of my minimum baseline in predicting yeild.

    HelloAll Member

    Seriously? 'Cuz after searching around most people that ask get told that it's more like .3-.4 grams per wat. .5 grams per watt is apparently for a pretty decent grower. What are your yields, light, medium and grow method, budbro?

    CaliClosestGrower. I'm looking into that at the moment. Thing is I was going for the Lumatek ballast because they have a 5 year guarantee and the Exolux ballast you pointed me to only has a single year guarantee. The Lumatek 600 watt dimmable ballast can only be reduced to 360, and 400 which isn't any different at all. Having a 250 option may be helpful during the hot summer months and if I ever deicide to veg in the tent... The Exolux can only be reduced to 300 watts by the way.

    nick88 Well-Known Member

    A 4x4 is a lot bigger than 2x2

    prosperian Well-Known Member

    My advise, based on your requirements above, buy a 400W light with an enclosed fixture. Absolutely use a cool tube with an in line exhaust fan to control heat and to keep the light tucked tight at 12" to the canopy. Forget about the open reflectors and your items aboove 1-4. My grow room is 2 X 3 and I run a 400W. 600W would be overkill.


    Grow Room


    bigv1976 Well-Known Member

    Run as much light as you can cool. If you can run the 600 and keep your temps under 85 then go for it.

    HelloAll Member

    Nice looking plants propserian. What kind of dried yields are you getting and are using the SOG method? Soil or?

    bigv1976. Do you think I will be able to cool a 600 watt light with my setup? And surely there's a point where there are too many lumens and most of the light is just wasted? Isn't there an ideal number of lumens per square feet? I mean isn't the sun 10,000 lumens per square feet?

    bigv1976 Well-Known Member

    Sounds like you read stuff. Very rare here. It makes me much happier to help. There is a point of diminishing return on light but I dont think it is so pronounced that you should pay it too much mind. To answer the question about cooling a 600 in your set up it would depend mostly on ambient temps. My ambient temps are around 60 and I can easily cool a 600 in a small space. With the proper fan your temps shouldnt climb about ambient by much more than 10 degrees so if your ambient temps are no more 70-75 you should have no problem cooling a 600.

    Jozikins Well-Known Member

    In a 2x3 space I used to make some banging ass buds with a high lumen 400w with a nice compact narrow hood for excellent light penetration, now I grow in a larger area and use 600w with a wide hood for a larger foot print, but it sacrifices a lot of penetration and I'll be going back to a narrow hood. Nice thing about euro hoods is they are adjustable, nobody making air cooled hoods is willing to put a batwing in a a/c housing because it'd lose way too much market on the fixed a/c hoods. But I still suggest a/c hoods because it makes heat so easy to control, and with a 400 or 600, you do not need to worry about toasting your buds. If you live in a real cold area and can keep your tent cold, you will get more UVB from using a batwing or euro hood, which would be cut out by the lens of the A/C hood.

    But you know what, you can find 400w digital ballasts from a good name brand for dirt cheap if you look around. Some of my best all time yields (gpw) were way back when I first started in that 2x3 space as a hydro experiment. I used the 400w because I didn't want to burn up a bunch of electricity experimenting with DWC. I don't have any of my old journals laying around so I couldn't tell you what I was getting, but it was pretty good, probably around .85gpw, or .87gpw, or something like that sounds right.

    Don't get me wrong, if you went with a 600w, they are the most efficient. 400w has really come up in the last few years, like the Digilux and SunMasters, which are really bright at first, far brighter than comp, but burn out much faster (I say it's totally worth it.) I love 600w, and when I couldn't make the decision at first, I just bought a NexGen 400w/600w switchable ballast. But I tell you, I got two of them and they both burned up on me at least once or twice. The most recent replacements have been going strong for 2 or 3 years now. I'm just glad I had a very reliably designed magnetic ballast to back it up (BTW you can only use ceramic MH in a magnetic ballast,) I don't normally use that mag ballast except for experiments because magnetic is a pain in the ass to deal with, except when you need something dependable, haha.

    This is your first grow right? I haven't ever used or talked to anyone using Jardin, but I hear they are good, whatever has the very best roof supports is what I recommend! Expensive lesson I learned, 2 or 3 times over!

    What are you going to grow in? Soil, soiless, hydro? It's all great, just keep your containers up off the concrete in the basement, and keep your humidity down. I personally think the basement is by far the best place to grow pot, and strategically picked my current place because it was the only house with a basement in my area, it's a small basement, but I have a decent sized window to the outside that I draw lots of fresh air through. Lots of fresh air really helps in a basement, and is really required for any grow.

    Are you in a forested area or or a area with a lot of foliage on the ground year around? A area with lots of farm land? If yes, or even still if no, highly consider a high quality filter for your air intake to prevent mold. I'm in a area with lots of foliage on the ground year around, and PM is always a threat in my garden. I plan to replace the filters soon when I scale down my garden in the next two months.

    Have you purchased your nutrients yet? I recommend if you are starting off to get some cheap, easy, and super effective. For small gardens I highly recommend Technaflora's Recipe for Success, it's a 35 dollar nutrient kit and for the money I've never seen such a small kit be so effective. Follow it's directions at 50% basically allt he way through and it's hard to fail. PH and PPM testing equipment is mandatory in any grow as well.

    Probably a lot more info than you asked for but let me know if you have any other questions and good luck growing!

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