How far should HPS be from plants?

[SeedKing72]

How far should my 400Watt HPS be from the top of the canopy of the plants?

[Sentinel]

If its too hot for your hand its too hot for the plant.

[SeedKing72]

Well I will try that, I found in a book 18-24 inches for a 400Watt

[HARDDON]

Seedking...

Its about the heat your plant will feel from sitting in the same spot for hours on end. Your hand will only tell you if your hand is getting burned.

It depends on the air temp, circulation / ventilation environment and the use or not use of a reflector.

For example, I can get my HPS in my hand and it wont burn as long as the fan is right on it. But after a minute or so I can begin to feel the heat rise.

Plants are the same.

Just start out high and work your way down. Keep the temp guage right between the lights and the canopy spacing.

In one of my threads, I get the MH within 2 inches of the canopy....but as the air temp changes because of the garage, I need to adjust it accordingly as well.

Place safe and work down....starting at 18" without a reflector and at least 24" if you are using a reflector.

Good luck man :)

[Garden Knowm]

Well I will try that, I found in a book 18-24 inches for a 400Watt

FUCK NO!!!!!! please, please listen to this... 18 inches is a fargen joke.. you loose more than have the POWER.. hal the lumes.. whatever the f-k that is...

anyway.. strong vegging plant should be 1-5 inches from the light... just put a good fan blowing between your canopy and the ligt..

good luck!!!!!!

[HARDDON]

His plants are very young.

A 400W HPS will fry them in hours 5" from the surface...even with a fan.

It could fry them within an hour if there is a reflector present to the 400W HPS light at 1 - 5"....

His plants are very young gnome. :)

[9ski9]

MJM rejected you Knowm? Sorry, dude.

I have two fans blowing from two directions pretty hard across the plant tops and 400w HPS bulb and 6 inches is the absolute closest I can get them.

[SeedKing72]

That damn light gets hot, it was like 90 in there.. I have two 22 inch box fans in there I turned the one that is blowing the hot air OUT from the ballast on high and it got down to 84 with the window open in that bed room... The other fan is blowing between the canopy and the light.. but I couldnt turn it on too high, because it looked like it was a hurricane in there... and I thought it might damage the plants.. As they get bigger... they might be able to handle it..but not now..