Design vs. Heat....question??

[dank.frank]

assume a given area of 2' x 2' x 3' tall. that is 13 cubic feet.

If I use a 4" can-fan (142 cfm), that should be more than sufficent for my air venting needs...however,

If I decide to run a 400w HPS in a Hydrofarm Radiant hood (using the vent flanges and hooking the can-fan up to the top hole in the hood) will I still have enough air movement to keep my temps down?

The air would be being pulled out the top center of the environment, right above the bulb, so heat would all be pulled right up, in theory...

I also plan on fitting the area with small 90mm fans that will be air intakes...2 near the bottom middle, and two near the top, and each fan moves around 30 cfm...so 120cfm on intake and 142cfm inline fan for exhaust.

Will my temps with a 400w HPS be managable, or should I consider a smaller bulb.

 

[C21H30O2]

unless your running the bulb bare and vertical your gunna need a bunch of ventilation. if you made it taller that would help.

 

[00420]

my first? would be is that 3'tall with light or with out? i ran a closet that was 2 x 2 x 4 (with light) and a 400 was fine {in winter} i was using a 265 cfm fan dont chimp out on light do to a fan...... i even steped up to a 1kMH for flowering again... this was in winter and i was blowing in fresh cool air from outside... in summer i would have never beenable to do it with out bringing in cold air so make sure thats in your "Design" i would say go for the 400 and look into steping up to a 2nd canfan {maybe a 265} but allso make sure the air your bring in is cooooooooL..........

 

[dank.frank]

3' of vertical space and then the hood. So figured 3'4" to the bulb itself.

How hot should I expect temps to get on a 400w bulb? I have no way to draw cold air...not an option.

Best I could do, is add 1 more 90mm fans to each side of the hood (it has 3 total 4" vent holes) That would be 60cfm of air directly blowing over the bulb, 120 cfm blowing into the area, and then the 145cfm in-line extracting the air from the top/center of the area, and blowing it out a 4" odorsok.

Is that gonna be enough...or am I looking at a bigger in-line or a smaller light setup???

 

[TriIron]

assume a given area of 2' x 2' x 3' tall. that is 13 cubic feet.

If I use a 4" can-fan (142 cfm), that should be more than sufficent for my air venting needs...however,

If I decide to run a 400w HPS in a Hydrofarm Radiant hood (using the vent flanges and hooking the can-fan up to the top hole in the hood) will I still have enough air movement to keep my temps down?

The air would be being pulled out the top center of the environment, right above the bulb, so heat would all be pulled right up, in theory...

I also plan on fitting the area with small 90mm fans that will be air intakes...2 near the bottom middle, and two near the top, and each fan moves around 30 cfm...so 120cfm on intake and 142cfm inline fan for exhaust.

Will my temps with a 400w HPS be managable, or should I consider a smaller bulb.

My math says 2x2x3 is 12 cubic feet, but that is just nitpicking.

My first grow was in a homebuilt cabinet with a 250 that was only cooled/circulated with 2 computer fans, and temps stayed in the mid 80's. I can't imagine a 400 would put out so much more heat that having a 142 cfm fan wouldn't cool it adequately.

 

[dank.frank]

yeah, sorry 12 cubic feet...typo, sorry.

hmmm...anyone one else with any thoughts our input?

 

[Murphy]

Here's what I did, maybe it will give you a different idea. First, let go of the air cooled reflector idea, you're paying to much for a bent up piece of metal and glass. 400 watts or below can be cooled easily by "shelfing" the light. I took an umbrella reflector and recessed it into a "shelf" in my cab. I raise and lower the shelf. You can do this one of 2 ways depending on your set up. I cut my intake above the shelf and mounted the carbon scrubber inside the cab. The air is pulled from above the light and the only way for it to get into the cab is through the panel in the light where the light mounts. Or you can put your intake low and pull from above the shelf, with the closet/cab under suction, the air is always being exchange.

Here's a crappy pic, hopefully it gives you the idea your looking for. I run 400 watts in with a grow area of less then 8 cubic feet when I have the light dropped. I keep the bare bulb 5-6 inches off of the canopy.....that's closer than I've seen some people do with an air cooled reflector.

As for your fan, a 4 inch inline fan is all you will need. Mine in on a speedster and I keep it running at about 65-75% NO NEED FOR A LARGER FAN. You can actually do it with a stanley blower for $40. I also have a 4 inch axial fan that blos directly on the bulb.....don't let it fool you, that is NOT a computer fan, it's 110v 130 CFM fan in the upper right corner of the first pic

 

[dank.frank]

nice setup murphy...

I already have the equipment I am discussing, I have just never actually taken the time to set it all up and use it....for some stupid reason.

So I DO still plan on using the air cooled reflector, I just want to make sure that my temps aren't going to be too high using the fans that I have....

 

[Guest]

make mention that murphy is running a CMH which may be how he gets his numbers right and lights so close...

 

[dank.frank]

bump....hmmm, nobody else has any input on using a 400w and what issues I may face when dealing with heat???

 

[Hawk]

I went through a similar decision recently. I need/want my "lights on, door closed" cab temps to be within a few degrees of the ambient air temp. So I was really focused on temperature. 250 vs. 400, 250 vs. 400, back and forth. I was conservative and went with the 250. I have not been disappointed with my first attempt so far (27 days into 12/12).



I'm cooling with a SS2 hood, 6" EcoPlus (440cfm) pulling through a (probably larger than necessary) DIY carbon scubber, and 50 feet of 6" ducting. Much of the ducting is rigid and some thought was given to bends and such, but still--it's a 50 foot pull. All intaking is passive. By feeling the fan exhaust, I have to believe the actual amount of air being moved is maybe half (?) what the fan is rated for. Maybe less. My space is larger at 22"D x 39"W x 59"T. My temps have been good, averaging around 1-3 degrees above ambient an inch or three into the canopy.

I would LOVE to somehow borrow a 400 watt bulb and ballast for a day just to see exactly what the temp difference would be. I have NO experience with other wattage HID bulbs. But near as I can guesstimate, I bet I could handle a 400w CMH just fine. I could probably do a 400 HPS too if I sealed up my cab better and did some other incremental things to boost cooling performance.

I'm actually considering adding another lamp to my hood. Another 250w or add a 400w for 650w total. If I go to 650 I'll add another 6" fan--one dedicated to exhausting the lamps and the ballasts, and the other just exhausting the cab's volume. I installed dual 6" lines up in the attic for that long pull so much of that ductwork is already done. Even if I only go to 500w total, I'll still probably add a fan. The coolest air I can bring in is about 76 degrees (central AC) so to stay below 80 I don't have much wiggle room.

I may very well find that the 250w I have now is more than adequate to suit my needs. So far so good.



I have no idea if any of that actually helps you. But that's what my experience has been------->didn't know between a 250 or 400, went 250 and have been happy but probably could have gotten away with a 400 in my setup.