How close it too close?

[etinarcadiaego]

I'm vegging 5 plants under a 400 watt Metal Halide in a sealed reflector hooked up to centrifugal fan.


How close can I get my plants to the reflector glass? The temperature, as taken 2" below my glass with a thermo probe ranges from 68F - 69F over 24 hours.

Please let me know your thoughts.

 

[resin_lung]

I like to keep them about 10-12 inches with a similar set up.

 

[CannabisSativa]

I've had my cool tube about 6 - 12 inches from the tops of my seedlings right when they went to veg stage, then later on I moved the light up further so that they all got good light coverage. I think the key is to not worry about how close you can get, but to efficiently place the light to where the entire canopy gets light.

I also use a 400 watt MH.

 

[Vegan]

I like to keep them about 10-12 inches with a similar set up.

 

[Hank Hemp]

Hold the back of your hand at plant top level, does it get hot? burn you? Then it will burn your Babies. 10-12 sounds good otherwise.

 

[emeraldtri]

Well, I had my 1000w at about 10-14 inches and I got all kinds of light burn. Wasn't too hot on my hand either. I can only assume that it was UV or IR Rays that caused the damage, not just heat....

 

[OCdirty]

depends on the heat....if it's not an issue I see no problems with them being right on it.

 

[K.J]

It definitely all depends on your setup. I have a 250 that's supposed to be air cooled, but I don't have it hooked up to the ventilation and I took the glass off the front. A few of my ladies are within 6" and they're doing fine (of course, there's also a steady wind from the centrifugal fan blowing across their tops).

 

[BLUNToPOTomuss]

as close s you can hold your hand without burning. I have a 400 HPS in a cool tube and I am about 4-6 inches from it. Just payattention, and make sure as you move the light closer you are not getting any light bleaching..... If not you are good!

 

[etinarcadiaego]

Awesome thanks. I keep my temp probe in the canopy of my tallest plant, which is like 4" off the glass. It's range (during my 20/4 cycle) is 66F = low, 76F = high.

That sound ok?

 

[CannabisSativa]

Great temps man

 

[RipVanWeed]

I run a 1K vertical cooltube, I let my flowers grow toward the light till their about 6" away, then start to tie them back.

I have to admit I've bleached a few leaves and on my last grow I had to trim off a couple of grams worth of toasty brown bud.

I thought this was OK because otherwise I may not have used all that expensive light to it's max.

Respect,

 

[BeanSprout]

Too close

Too close

...is when the leafs and buds burn and turn brown. Then it is sample time

bs

 

[CanadianGrower]

A good rule of thumb is but your hand on top of your plants canopy for 1 or 2 min, if your hand burns or feels very hot its to close.

 

[pip313]

etinarcadiaego:
How close can I get my plants to the reflector glass? The temperature, as taken 2" below my glass with a thermo probe ranges from 68F - 69F over 24 hours.

if your sure of those readings from the thermo probe than 2" is fine. Just keep checking at first for light poisioning/bleaching.

 

[RockyMountainHi]

Start with the light a little too high - let the plant tell you; it will start to change form when it's too close.

That is sooooo much easier than guessing wrong - and it may not yeild a gram or two as much, but it won't risk a decrease due to over exposure.

I'm running air cooled hoods for the first time also - but my lights are 1000W and on a mover - the plants are happier farther away from the light than I had planned - and the light isn't stationary. fortunatly - I haven't had to raise the roof yet - but that's always an option. I thought because of the mover - the tops could easily be 12" away -- 18-22 seems much better with most the plants I have in flower currently - and some plants may want more - some less.

 

[VerdantGreen]

also it is worth remembering that if your light is too close your reflector wont spread the light evenly over your plants - you just get one very bright spot in the middle.

 

[etinarcadiaego]

Thanks for all the help. My plants don't seem to mind being close to the light. I'm vegging 20/4 and my temps are 68F - 77F over a 5 day period. I'm moving a LOT of air through my cab, which is only 36 cubic feet.

This is from Monday: