Using HLG UVA 30 light supppliment & VPD

Any input on how to set up VPD while using a UVA 30 watt suppliment light? It is on for 3hrs in middle of 8 hr light cycle.
I set up my offeset with it on. I will recheck with UVA30 off. My offeset will probably go from a neg 2.5 (-2.5) to a zero. Thinking set offset to a one (1)???

4 x 4 tent, HLG 550 R Spec/ HLG UVA30 / running CO2 @1500ppm avg

Hey @FrostyGT

A -1 offset is probably your best bet for that scenario. Even with the lights off/low, the leaf temp will still be slightly cooler (generally) due to the transpiration occurring on the leaf surface.

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TY, I’m gonna run with that, (-1).

On the discussion of supplement lighting has any one tried hlg 60 w red supplement? I have one running with 2x hlg 100 3k lights 2x4x7. Been doing alot of research on far red and when to use the light. For the last week of veg I was running it on a full 18/16 with 15 min after lights out. This in theory makes the plant transition to the dark cycle faster simulating a sunset. Anyone have experience with deep red/ far red supplement.

I’ve tried it also with little noticeable improvement. It seemed like the transition into flower was a lot faster but that was like the only definitive difference that I could :100: say I noticed for sure at 680 nanometers. Been looking for ir strips but they are hard to find bc they’re a bit more expensive

Hlg recommend running there 60w bar during full light it also has a mix of blue spectrum working in conjunction with deep red 660 to far red beyond “the photosynthesis spectrum” at

Curious about the recent studies done on this and the Emerson effect not a crazy amount of info on it other then Bruce Bugbee youtube

Keep you posted

Most of what i have read on UV is that it can stimulate gland head growth in flower. So I don’t use it during veg, only in flower and only for 4 of the 8 hrs light cycle. Most of u have more experience than I so I’d also like to know more of what u guys learning.

RECHECK YOUR LEAF TEMPS WITH UV ON AND OFF. UV can significantly raise leaf temps.

Just installed an hlg 350 r which has a dimmer setting upgraded from 2 100 3ks

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