My grow room is 4ft wide x 2ft deep x 8ft tall.

I am currently using 1 400w HPS, which for flowering is on between 8pm and 8am.

For extraction, I'm using 2 RVK150A1s (420M3/h each). One is pulling air in from the loft and the other is extracting the air to the outside world via a roof vent.

My temps at the moment never go above 25*C.

I am going to Amsterdam at the end of August and thought I might use the opportunity to buy myself a cheap 400w HPS to add to my room (at the moment, the light doesn't spread right to the edges of the room, most of it is focused in the middle).

Do you think the extra heat created by another light would put my temps up too high?

Thanks
Chez

Hey.

As long as you kept the light a save height above the canopy then you should just get better growth.

If it's too hot though you should remove immediately, your plants would recover within a week.

Laters.

Peace, love and empathy.

blacKdeath

Thanks Blackdeath.

I know I could remove it if it was too hot, but I'd rather not have to shell out the money on a 400w when I may just be better off getting a 600w to replace my 400w.

Hi chez

I think that so long as you have a ready supply of cool air and your moving it through fast enough, and it sounds like you are , then you should be able to add another light no probs.

Please don't sue me if I'm wrong

npk

Hi NPK.

Like you, I'm thinking it probably would be OK, just not sure!!

I guess I'll have to just try it!!!

Hi,
Just a thought, how about buying a cheapo 500w halogen spotlight and putting that in there. You can get them for less than a tenner and the heat that would throw out is probably worse than a 400hps, it would allow you to test your setup without buying a new HPS that costs a lot more. Obviously the halogen is no good for growing, just as a test.
RM

hell chez

IMHO i reckon a 600w would be cool, at present it is THE most efficient bulb today. having another 400w may increase your temps too much as you will have 800w of light in a grow space of 8 sq feet.

this equates to 100w of light p sq foot, plenty of light there, but the temps.....ARGH THE TEMPS!! always sommat aint there?.......

get a 600w, use the 400w for vegging? just another option.

as your temps are good at 25C, you only really have 4 degrees leeway....anythinhg above 30C is prob a little too warm (as i have found out!)....

as you say in your post, the light doesnt reach the sides, has this effected your yield or plant growth in anyway?

sorry, probing for more info.....mindya, riz's idea is a gud un and use the halogen for temp check first!

peace & respect.
BB

Thanks guys.

budahbwoy - The light not reaching the edge is a bit of a problem as I'm currently in the middle of a Scrog-type grow (albeit from seed) and the edges of the screen aren't getting enough light.

Chez - I'd go for the 600w option, however, you could go for 400w with an air cooled shield. Not much more expensive than a normal shield (£15 extra for Supernova) and you could cool it with your exsisting fan set-up.

Hi chez,
as NPK says, if you got the through put and nice fresh air,
should be ok, i started with two 400w (one sodium and one halide)
and had good result, you can do more with the light spread with 2 lamps
if it dose get a little warm, a slight mod to the extraction should be
able to sort that with your pulling power
good luck with what you choose
UFO

Thanks guys.

Cowboy - I'm considering air-cooling the reflectors, seems the easiest way to get rid of any heat problems! (or getting a sheet of glass between the lights and the plants)

UFO - did you ever use just one light? If so, did the addition of the second make a lot of difference?

Thanks
Chez