Metal Halide for Soil Setup

[primlantah]

400W metal halide for a 2.5x2.5 area. Was 8 inches from tops of plants with temps ranging between 80-85 daytime. The only ventilation is 1 12 inch oscillating fan blowing on hood and plants. Another oscillating fan blowing fresh air into the room.

I have seen alot of posts saying put it as close as possible and still maintain reasonable temps. I understand my temps are at the threshold of being too hot. The plants seem to be developing fine overall. The There are a couple yellowing and curling and a couple doing perfect. There was no stretching on any of them. Since they are showing inconsistent results i began thinking about raising the hood to about 2x the distance as before. this would be 16 inches from the tops of the plants. From what i have read 18-24 is ideal for a 400W MH.

Should i raise it or leave it?

 

[edsthreads]

I have a 400W HPS lamp just 12 inches from top & plants seem to love it - I also have fan blowing onto top of plants & lamp & one fan sucking clean air in

 

[bifter]

I have a 400W HPS lamp just 12 inches from top & plants seem to love it - I also have fan blowing onto top of plants & lamp & one fan sucking clean air in

me too and it all seems ok,they say to put your hand where the plant tops are and if it burns you its too close
Bifter

 

[kieahtoka]

that's so weird, I can't put mine closer than 2 feet to the tops of my plants or the temp goes above 90 and it's uncomfortable to put my hand there.

 

[primlantah]

I raised it to 16 inches from the tops of the plants. I noticed the thermometer read even higher temps than before(90-93ish). However, the leaves are curled less and are less yellow. Before i moved it i thought the light felt fine on the back of my hand. I think the temperature readings before were from a poor location relative to the plants.

Is 85(the best i can achieve with both fans on the plants) too hot for growing without CO2? And if so can i really raise this light more without thinking about supplemental lighting? I guess i should throw in that they are all seedlings currently about 2 or 3 inches in height and 25-30 leaves each.

 

[420101]

good ventalation is key i keep my 400 no more then 6 inches away......

 

[Widow Maker]

good ventalation is key i keep my 400 no more then 6 inches away......

Exactly. I have cool tubes and have had my 1000w lights 2 inches away at times. The light mover helps you keep it closer too. But for a 400w I would say atleast 12-14 inches if its a bare bulb.

 

[primlantah]

the bulb is in a vented hood but there is no duct hooked up to it. Cutting the house is not an option so i am trying to use fans to control the heat. This is not the best way to go about it but is the best i can do. if i am only supporting 4 plants and expect to reduce to the best 2 before the end(unless they all turn out ok or better and space allowing!) will i need to think about supplemental lighting at <= 18 inches?

 

[420101]

i think you got lots of light to meet your needs and i keep my 400 6 inches above without a vent hood just check using the back of your hand at plant level thats were i check the temp too

 

[primlantah]

got a fan for it and the plants can touch the glass fine. great investment