HPS power vs heat

I am sure that this has been covered on some level here, and I have searched, but I am having a hard time finding any concise detail on exactly how hot HPS ligts are... how much heat to they generate and how far from your plants do need to keep them? (I mean, I know, keep them as close as possible without burning your plants - but how close, on average, approximately, for a system with 600w bulbs and air cooled reflectors is that?)

To elaborate:

I have limited vertical space (not quite 5' from floor to ceiling) where I am planning my new setup. I do have a lot of horizontal space, about 25'x20', and ventilation is no problem. I intend to flower with 3 x 600w HPS in air cooled "Cool Sun" reflectors with the glass bottoms and 6" ducts and fans, cool air from outside, vented out of the room...

Can somone with some experience with these lights give me their thoughts on whether they will be too hot to use in this limited space - I mean if my plants, along with their pots, are 3-4 feet tall, that would leave the tops like a foot or less below the glass bottoms of the fixtures. Is that going to cook them? Even though these are air cooled fixtures / reflectors?

Would I have less of a heat problem if I used like 4 x 400w HPS in same / similar air cooled reflectors or even 6-8 250w bulbs?

I mean, how hot are these things, really?

Flourescents: proximimty
400w HPS: 1 foot
600w HPS: 1.5 foot
1000w HPS: 2 foot

You rock bro, thanks! Hey HTF do I give cred or 'reputation +' to other users on this board; I searched for it on the board instructions and in the FAQ and it said something about using the little scales above the users ID on their profile page. I dont see any scales? wtf?

So if I am going to go with 4x400watt HPS... does anyone know of ballasts that can run more than 1 bulb? I have never seen one of these, but I dont want to have to buy 4 ballasts.

I would go with the 600s, they are the best lumen/watt ratio, even better than the 1000s. And the Cool Sun hoods are great, really low profile and still a nice spread, and the 6" ducts will take the heat away. Just be sure to vent those correctly, and you'll be fine.

You'll need 3 ballasts. If you duct the 3 hoods in a row, put a blower on one end, and a sucker on the exiting end. Of course you want to exhaust that air, but pulling the air into the lights from outside is nice, too, especially if you want to add CO2.

Yeah, if I helped you and you want to thank me, just click on the scales next to my post number 4 just above.

like you need the rep pot lol. Its like the scales of justice not for weighing ozs rofl. Sorry just alittle brain fart there.
There are ballast available now that will run two lights. At the shop i visit, they have been in business since 82 in this location, the owners son said he could hook me up with one ballast that will run two 600w fixtures, sheilds and glass, with the attachments for ducting for about $650.00. They have it displayed and it kinda caught my eye. Pot is right. I'm looking to upgrade from my 400watt to the 600watt.

AetvsDominvs said:

Would I have less of a heat problem if I used like 4 x 400w HPS in same / similar air cooled reflectors or even 6-8 250w bulbs?

I mean, how hot are these things, really?

Click to expand...

I agree with potroast, 3 x 600w HPS's would be better than 4 x 400w HPs. The 600w HPS is the most efficient in terms of lumens per watt of any of the HPS systems. 3 x 600HPS's would output 3 x 90,000 lumens = 270,000 lumens, the 4 x 400w HPS's would output 4 x 55,000 lumens = 220,000 lumens. Plus the 600w systems would be only marginally more expensive to run, 3 x 5.7amps on a 120v system is 2052 watts, 4 x 400w would be 4 x 3.8 on a 120v system would be 1824 watts. So for 228 watts more you get another 50,000 lumens.

The air cooled reflectors, if set up properly would allow you to get your reflectors to within 12 inches of the plant tops without burning them, even lower depending on how efficient your ventilation system is. I think it would be a bit much to expect the vent system for the 3 air cooled hoods to also ventilate the area as well, so you'll have to set up a separate system for ventilating the area, probably with a charcoal filter.

Don't veg with the HPS's though, get some MH conversion bulbs or switchable ballasts that would allow you to switch over from HPS to MH for vegging. There are ballasts on the market than can run two lights from them, but they're not cheap. Aurora do an air cooled reflector and twin 600w ballast, but it's about 1000 USD.

plants veg just fine under hps, conversion bulbs are a waste of money if you have hps to begin with, i clone veg and everything under a 600 hps, get a fan blowing across the lights even if they are air cooled and that will let them get within a foot of the lights