Newb with a couple questions

[Riverwart]

Hello, 1st post, here.
trying to get equipped to make an attempt @ growing. Looking to do 1, maybe 2 autos in soil. Have planned out the particulars, but I have 2 questions before moving forward.

1. Choosing a light. Very small grow space. Going by the "50-60" watts per square foot calls for 150"ish" watts. I am planning to go LED with the hope of using 1 light fixture. Will add strips if needed, but would prefer not to. My question is this:
Can I use a dimmable 300w light with the intensity dialed down in a space that calls for 150w. In other words, does a 300w turned down half way= the potential to "light-bleach" a plant as a 150 at full strength. Thinking a bigger light will be more useful in a larger space down the road, but dont want to torch my plants in my current space. Light will be recessed into top with cooling fans outside of grow space. The specific light Im interested in is a viparspectra dimmable 300w, but completely open to suggestions.
2. Ventilation
Grow container will be outside, completely shaded. Daytime temps tend to run upper 80's with high humidity. Plan is to have short passive intake(2-3' straight-run of 4" duct hose/pipe) drawing air from the air-conditioned indoors. Was thinking of going with 6" exhaust line/6" duct fan to pull air out. Is it crazy to think this could possibly move enought air in a 2'x2'x3.5' closed, air-sealed space?

any input or suggestions are most appreciated very much
thanks for reading.

[Campesino]

Is the grow space you are planning only 2'x2'x3.5'?
You can put a Viparspectra 300 in a 2'x2' space, but not if it is only 3.5' tall. If you plan to use LEDs you will need a much taller space.

I don't really understand your ventilation question. However, if you plan to use passive ducting, it should be larger than the active exhaust. But to give specific advice, we need to know the dimensions of your grow space and you may need to reconsider height.

[Riverwart]

Thanks for your response!
Growspace is 44gal brute can stacked 2-high.
For ventilation, trying to pull enough air from indoors (air conditioned & dehumidified) thru a 2-3' intake-line to keep the temp closer to the inside temp of house than the temp outside where the can is going to be sitting. Wondering how big of a fan I need & what size venting would it take to keep enough cool air coming in to offset the heat the can will be resting in.

[Campesino]

Again, What are the dimensions of the grow space?

[Campesino]

For venting:
6" line from house to Grow space, Passive
4" Exhaust fan ~200CFM

The exhaust fan will pull air through the passive intake.

[Campesino]

I should say, The exhaust fan will create negative air pressure in the grow "barrels" which will pull air through the passive air intake.

To tell you anything about lights we need actual measurements. I am not loving the two barrel idea/

[Riverwart]

Round refuse bin. 24" diameter, 42" height.

[Campesino]

So about 84" total height, or that is already the total height?

You are not going to want to put more than one plant in there, but if total height is 84" you could put a Viparspectra 300

[9fingerleafs]

Go CFL. You are building a space bucket

[Pyro1711]

I agree with 9fingerleafs CFL will also run cooler than the LED light which should help keep your bucket temp down.

[Redwasp]

Yes it sounds to me like your making a space bucket. Ive never tried that but heard decent success stories for the space. I know others may disagree but my plants in the veg state really liked temps higher than that, outside with real air. In a space bucket type setup no clue. I had a mishap and had to move mine for awhile a time back. Went from 72 degrees to close to 95. 4 days later when I got them back they had doubled in size. Go figure.
But yes for the space i dont think an led would be the best and by far not the cheapest option. (Unless i misunderstood your setup." Again never tried what you are trying but other than cooling they need at least a light breeze. Thats seperate from ventilation. Especially when flowering. And in the flowering stage they need lower temps.

Dont think I Said anything that will hurt your grow. Lol All my exp is outside with god watching my flowers or inside where god just shakes his head and says "if you think you can do better!" Ive gotten good but god still has me beat handsdown.

[Riverwart]

Sincere thanks for the feedback,

Yes, its a space bucket setup, but instead of using 5 gallon containers, I'm using 44gallon containers.
Campesino, total height of 41".
The reason I wanted LED was for the convenience of buying a plug&play fixture. Realize they cost a bit more, but in addition to being effective, Im also trying to keep it neat/clean with as few cords, & little wiring as possible. Assuming a worthy choice is available in the 100$ range, Im ok with the price difference in the bigger picture. Ambient heat is a major concern, but as the light goes, plan was to have it recess-mounted in the lid to keep the cooling fans&vents for the light on the outside, with the exhaust outtake positioned just beneath the height of the light fixture. Was thinking that'd be enough to combat heat from the light. The smallest dimmable, reasonably priced LEDs seem to be 300w. I realize a 300w light is a bit much for this space, but I suspect could be more useful in the future. If its dimmable & turned down accordingly, would it function the same as a smaller light. i.e.: would a dimmable 300w turned down half way be roughly equivelant to running a non-dimmable 150w? Could distance between light & plant be kept similar? Plan was to LST to try and control height to maintain 14-16" between plant & light. Could always add 8.5" spacer mid-grow if necessary, too. Have seen some diaries of impressive hauls out of identical container im using with a 180w LED + strips.
As far as combating the ambient temp of the location, Im hoping to create enough negative pressure to pull enough air from 73-75f(23-24c)air-conditioned room, via 3' straight piece of duct pipe. Typically summer temp difference from in/outside is 12-15f (6-9c).

All that said, Im always willing & hoping to hear a better way! Would love to hear any thoughts suggestions.
thanks!

[Redwasp]

Well get at least. 4 inch exaust fan and 4 inch ducting. Will help in the futore.