Uva dosage
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Moflow
Well-Known Member
I've these cheapo 385nm uv-a running at moment.
I started off with 4hrs for a week or so, then after inspecting plants for damage and finding none I upped to 8 hours on.
It's only 30 watts total, 20 watts uv-a and 10 watts 410-420nm blue in a circa 600 watts of samsungs.
I'd probably be better off with a reptile uv-b T5 fixture of 30 - 40 watts in there.
Uv-a shouldn't cause any problems for plants but too much uv-b is detrimental to plants and your eyeballs and skin.
My uv-a is ALWAYS OFF when enter the room.....
I can't find much info on anyone using / experimenting with uv-a .
whitebb2727
Well-Known Member
I ran the 10,000k+uva t5 bulb from agromax at htg supply. 54 watts. Not sure of the actual uv output.
I can say the uva does provide benefits when growing. Makes pot a little better. Helps prevent mold and pm.
I can say the uva does provide benefits when growing. Makes pot a little better. Helps prevent mold and pm.
whitebb2727
Well-Known Member
Yes. The pure uv bulb. It needs to be about 3 feet off the canopy and run on a separate timer for a few minutes on each hour.
The 10k+uva bulb can be run full time.
Agromax makes it. Htg supply just sells it.
HydroRed
Well-Known Member
I was gonna say....12 hrs with uvb, sounds like your plants will be dead in a day.
Aolelon
Well-Known Member
Well @Randomblame was saying he runs his 13w reptile for the full 12 hrs
Randomblame
Well-Known Member
Yeah, a Reptisun 13w(10%/30% UVB/A) above 3ft² and 39w Arcadia (12%/30% UVB/A) above a 10ft² area. The 13w is a 1U compact bulb and the 39w tube is a T5HO.
At 8" the 13w bulb is ~150-200μw/cm² and the 39w tube reach the same intensity at ~16".
For the last 4 weeks they run parallel with the mainlight(300w strips/COB's) and there was no visible damage. I've started with 2+2h and increased slowly but the next run I'll let it run the whole time.
Below is a chart showing summer time UVB levels, with my 200μW/cm² it seams I'm well within the limits.
But the HTG PureUV tubes are more than twice as powerful as a 10%/30% reptile tube what means you will already get 440μW/cm² UVB at 12". This means only half the time is needed to get the same amount of UVB radiation and the light can be further away. 12h x 200μW/cm² or 5-6h 440μW/cm² is almost the same.
Unfortunately they are not available were I life, but I still get some within the next weeks and I'm looking forward to testing them.
Let's see how much it takes for the girls to get sunburned?!
Edit:
Below is a test with an 2ft/24w Arcadia T5HO with different reflectors.
At 8" the 13w bulb is ~150-200μw/cm² and the 39w tube reach the same intensity at ~16".
For the last 4 weeks they run parallel with the mainlight(300w strips/COB's) and there was no visible damage. I've started with 2+2h and increased slowly but the next run I'll let it run the whole time.
Below is a chart showing summer time UVB levels, with my 200μW/cm² it seams I'm well within the limits.
But the HTG PureUV tubes are more than twice as powerful as a 10%/30% reptile tube what means you will already get 440μW/cm² UVB at 12". This means only half the time is needed to get the same amount of UVB radiation and the light can be further away. 12h x 200μW/cm² or 5-6h 440μW/cm² is almost the same.
Unfortunately they are not available were I life, but I still get some within the next weeks and I'm looking forward to testing them.
Let's see how much it takes for the girls to get sunburned?!
Edit:
Below is a test with an 2ft/24w Arcadia T5HO with different reflectors.
Last edited:
HydroRed
Well-Known Member
I thought uv-b was much stronger than that @ 75% uvb/25% uv-a on the 2' Agromax "Pure UV" 24W bulb. I dont know the specs on it without digging but the bulb Aolelon is referring to is way more powerful than the reptile lights are @ 10%/30% & half the wattage. That bulb would require some great distance to not need to be run on a short cycle timer?
Randomblame
Well-Known Member
Nope! They are more powerful but not so much! On their website they have a chart showing UVB levels at different hights. And why not run the PureUV on a circle timer? It saves energy!
I you use it only half the time the mainlight is on means half as much power consumption from the UV bulb. In nature the plants also receive only a few hours intense UVB/UVA light, early in the morning and late evening there is almost no UV radiation.
For that reason I've tried it with 150-200μW/cm² for the whole day.
It needs probably twice or triple that much or more to harm the plants.
Imagine an nepalese Indika growing at the foot of the Himalaya at ~2500m above zero. The UVB level at this height is +1000μW/cm² (at a clear and cloud-free day).
Among other things, the trichomes serve to protect leaves, flowers and, above all, the seeds.
I you use it only half the time the mainlight is on means half as much power consumption from the UV bulb. In nature the plants also receive only a few hours intense UVB/UVA light, early in the morning and late evening there is almost no UV radiation.
For that reason I've tried it with 150-200μW/cm² for the whole day.
It needs probably twice or triple that much or more to harm the plants.
Imagine an nepalese Indika growing at the foot of the Himalaya at ~2500m above zero. The UVB level at this height is +1000μW/cm² (at a clear and cloud-free day).
Among other things, the trichomes serve to protect leaves, flowers and, above all, the seeds.
Randomblame
Well-Known Member
What I have read about UVB in other threads, the edges turn brown directly without turning yellow before, when the plants get's too much UVB so it can be easily distinguished from other things like nutrient deficiency or PH problems. As I said, after 4 weeks with an average of min. 100 and max. 200μW/cm² directly under the bulb there was absolute no visible damage. I stoppt feeding end of week seven and a few days later they began to show slight deficits (mainly N-deficiency down below and CalMag defiency of the upper leaves), but damage from the UV light I did not observe any and I observed pretty much this time because it was the 1st time with UVB.
whitebb2727
Well-Known Member
Depends on which one. One is 24 and one is 48 inches.
Aolelon
Well-Known Member
yea I meant the 2' T5, that's the one ill be getting
Randomblame
Well-Known Member
UVB/A levels are the same on both bulbs, the 4ft. only illuminates twice as much area as the 3footer.
Numbers are 440μW/cm² at 1foot and 170μW/cm² at 2foot distance. So useful output already at 24", with a sweet spot between 16-20" IMO.
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