Some info,

Size of flowering area about 2 x 3 x 4 feet, TD160 extractor, passive intakes, plants would be trained/scrogged to keep them fairly short so I should have about 2 feet of room between canopy and top of growing area, plus fans blowing over the plants.. does that sound ok to run a 250W in? I've been using 240W of Power Compact fluoro tubes plus ballasts which kick out a fair bit of heat and ventilation was never a problem, so I'm assuming the HPS should be fairly similar heat wise.. just wondering if that 2 foot(ish) of space above the plants is enough..

I certainly think its possible - using the td160 without filtration would keep it cool enough, but if you're pulling through a filter, I reckon you'd need to go up a size in fans (a td250, or the 4or5 inch jobbies from the uk420 shop).........I'm going to be trying a similar trick myself - cramming a 250w hps, fan filter and nft 205 into a total vertical space of 44 inches! - I've opted for the 4" fan and filter combo from the site store.......

And I'm thinking about a similar trick myself although I'm not sure I'm up to the NFT yet.

However I'd like to use a 400 watt over a single plant. I'm waiting to see if I can raise enough cash over Christmas for an air cooled glass screened reflector unit I've seen. Cost is approx. £90.

.......or a superspreader?(sooooooo cheap)..........mine's on it's way!............

Or four 200 watt envirolites.

now yer talkin! I've often thought that you could easily run them at 100w sq/ft no problem - then you'd be getting some really pokey weed, and lots of it!

I'll be very interested to see whether it's possible to work with an HPS with the very small amounts of headroom that you chaps have got available - if it is, I may give an HPS a spin sometime meself. I always assumed it wasn't feasible because of the heat and the need to keep the plants a sufficient distance from the bulbs, but if there's one thing I know about growing it's that I know bugger all. Shall keep eyes peeled for more developments .

several people have succeeded in the past - but it certainly isn't one of the times you can stint on fan power - the usual way of cutting the distance between the hps and plant tops is to use an aircooled glass shield - not a cheap option - I'm going to try the superspreader thingy in an effort to achieve similar results without spending a fortune - I'll be letting you know how it works!

The only thing that bothers me, however I could be completely wrong, i that using a HPS in such limited headroom means you can't get it very high of the canopy. As a result wouldn't this affect the light spread into the outer corners and edges. Maybe four envirolites, by their very design, would provide a better spread over a SOG or SCROG in such a small space?

Hope the integrated ballasts don't run much hotter either.

I don't think there's any doubt that the enviros are going to give you quite a bit more "headroom" I've allowed 12" out of my meagre 44" for the reflector, bulb, shield and "headroom" - take off 7 inches for the tank, I've got 25" inches of vegetation! - you could get it up to something like 31" with the enviros..................

Wouldn't have thought the light spread should be toooo much of a problem.. in my case I only want to cover about 4 square feet. Due to the different way light intensity drops off from Enviros and all fluorescents (compared to point sources like HID lights) they have to be closer which limits their spread aswell.. and the heat from 800W worth of Enviros will take some serious venting! People who think they're going to run cool are in for a surprise.