cooling a 150w hps in a small box

I'm in the planning stages of building a low budget semi-stealth grow box and I'm looking for some advice. I have a height limitation of about 40". I'm thinking of making it about 2'Wx4'L. I plan to build out of 3/8" plywood.

My plan is to get 2 150w HPS econolights, but I'm worried about the heat they'd put out. I've been reading through some old posts, but I'm not really sure what it would take to cool this. Ambient temps in the room it's in range from 40F in the winter to 100F in the summer. I'm wondering if a 12V oscillating fan, along with some passive venting would be enough to get me through the winter.

I'm on a pretty small budget right now, but I'm not willing to risk burning down my house. If I can't safely do it on my budget, I'll have to use CFL until I can get a little money saved. Any advice on where to get a cheap exhaust fan if needed?

I'm pretty comfortable doing electrical work, and I'm wondering if remote mounting the ballasts might help reduce the temps.

Any advice would be greatly appreciated.

A HPS in that small amount of space it will get VERY hot in there.

whulkamania said:

A HPS in that small amount of space it will get VERY hot in there.

Click to expand...

That's what I'm worried about. A couple computer fans or a 4" booster fan wouldn't be out of my budget, I just don't know if that's enough. I've seen people use more wattage in smaller boxes, but I haven't seen many specifics as far as cooling.

I think a couple T5's might be ideal for me, but that's probably a little out of my budget.

Good luck on your grow. HPS is a great bulb all around, but for vegging use MH bulbs with more of the blue spectrum for better growth. "cool white" tubes or spiral florescent bulbs give you the same spectrum with no heat. The hps bulb you would use when you decide to go on 12/12 lighting to "flower" your plants. Once again you have floro tubes or spiral bulbs in "warm white" you can use without any heat problem. Good to turn off MH or HPS and use florescent while you're away. Whiz Bang

Whiz Bang said:

Good luck on your grow. HPS is a great bulb all around, but for vegging use MH bulbs with more of the blue spectrum for better growth.

Click to expand...

MH is out of my budget right now, but maybe in the future if I can get my cooling issues worked out. Right now I have 2x26w daylight 6500k cfl to get my seeds started in their temporary home. I'm going to attempt to veg with them as well. I don't plan to veg very long before moving to 12/12 once I get my real box built. My ultimate goal is to sog, but right now I'm just starting from bag seed.

If HPS are going to get too hot, I can probably get a small T5 light and combine that with CFLs until my budget allows a few more T5's.

So many decisions...guess I'll have to put some more thought into it.

Maybe I should go with a 70 or 100 HPS instead of the 150. Or, maybe I could run an exhaust duct with a booster fan towards an outside vent that's pretty close to the box. I just haven't been able to find any info as to how much heat this light will actually put off.

Does a 150w HPS put off more heat than a 150w incandesent? Thanks for all the replies so far, all advice is much appreciated.

I just read the faq Someone oughta slap me for not looking there in the first place.

It seems like turning over the air every 5 minutes should be sufficient to cool a hot light. If I build a 4'x2'x4' box that's 32 cubic feet. If I understand correctly, I only need a fan to move about 7CFM?!?!? Doesn't seem like enough to me. Does that mean a 30cfm cpu fan would be plenty to cool off my box? If not, what am I missing?

I've done a couple of double 150 HPS grows. It does get quite hot. And those were remote ballast systems. I'm on a single 150 now and the room is a LOT dimmer. (ok, not a room , but a closet) But its just a single experiment plant. don't care if it produces or not.

4' high room is not much.

Pot will be about 1 foot.
lamp with buffer zone will be another foot or 1.5.

Doesn't leave much for the plant.

Remember heat rises. Have a 'head zone' for heat to rise to.

Fans don't cool, they just move air. If they move cool air to warm air the room cool. If they just move hot air, nothing gained.

as long as you have fans blowing cool air on the lights and into the grow space you should be fine.

SmokeyMcSmokester said:

as long as you have fans blowing cool air on the lights and into the grow space you should be fine.

Click to expand...

Maybe. Maybe not.
If the air coming off the bulb is staying in the room, you are getting hot air to the plants faster.

Cool tube!

Right now I'm just trying to absorb as much info as possible before I make a decision. I'm thinking of getting a couple small 30-50cfm pc or muffin fans to exhaust with, as well as a small oscillating fan in the box to move air around the light. I think this will work during fall/winter, but I'll probably have to upgrade once the ambient temps start to rise next summer. Anyone think I'm gonna burn my house down if I try this?