CMH Question

[slohemian]

Does anyone know the optimal dimensions for a 250w CMH horizontal bulb? I am going to customize my footprint to maximize efficiency. How about the otpimal footprint for a 400w CMH?

Reason i want to know is so i can have a good idea of how many clones i can throw in under them to flower.

 

[Guest]

I am using a 400W CMH in a 2'D x 3'W x 5'H box. 10 clones.

 

[slohemian]

gotchu, sounds great. thats almost the same dimensions as the one i want to build. The dimensions of mine may look something like this: width 24-36" depth 22-24" height not sure?

Reason for being unsure of height is bcs of venting and how tall my sensi star will get. If i take 1 clone per week i can do a 1 clone harvest perpetual cycle. sounds mighty fine

 

[slohemian]

QUESTION::

with a 250w horizontal cmh, whats the max footprint it could cover in plants...


my depth dimension is set at 22", what width would maximize a 250w CMH?

EDIT: the 22" can not be changed. Here is another Q, say i upped it to a 400w, what would the width change to then?

 

[PurplePotion]

You can have up to 75W/sq. ft. without CO2.. as long as you can cool it properly. Do the math :smile:

 

[slohemian]

thats not what im askin man

 

[PurplePotion]

thats not what im askin man

But it is. You have a fixed depth. You only have one missing vector. Simple algebraic equation.

50W/sqft is common among MJ growers not using CO2, so let's use this number.

So, you're aiming for 50W/sqft, and you have a 250W lamp.
With 250W, you'd be aiming for 5sqft.

X is your missing vector. 11/6 is your depth in feet.

(11/6)ft*Xft=5sqft
Divide 5 by (11/6) to find X.

5/(11/6)=~2.73 ft.
X=2.73 ft.

Same thing with a 400W, except you'd be aiming for 8sqft.

Your reflector and surrounding material determines your footprint for the most part.

 

[slohemian]

Oh alright, i didnt know u'r variable of 50w/sq foot is good.

 

[PurplePotion]

Yeah.. 50W/sqft is common, but like I stated previously, you're okay up to 75W/sqft. Just make sure you can cool it

 

[green_tea]

what are you suggesting to push WITH CO2?

100W/sq ft?

 

[wygram]

400 CMH on 2' x 2' area = 100w/sq_ft
Nothing bad about it.

 

[PurplePotion]

400 CMH on 2' x 2' area = 100w/sq_ft
Nothing bad about it.

Doubt your yields would be as great compared to having it spread out to 50-75W/sqft. Not saying that it's bad, but .. You can only shove so much light and so many plants in a certain area.

Here's a thread I turned up for you guys. Be sure to read all of it.. not just the first couple posts!! http://www.icmag.com/ic/showthread.php?t=84397

 

[slohemian]

So what would you say is the best wattage per foot?

 

[PurplePotion]

50-75. Anywhere in that range is fine.. just make sure you fill up your canopy and are able to keep your temps in check