What's new
By:
GrowWeedEasy.com
You're browsing as a guest. Sign up to join the conversation, share your grows, and get help from thousands of fellow growers — it's free and takes less than a minute.

Wanting to dial in my vpd

Same here. I'm trying to hit 60% RH and about 80f. The lung room I'm trying to keep at 68-70. With lights off the tent gets to lung room temp but not below. If I don't keep adequate ventilation the RH gets sky high with lights off. It's easier for me to maintain the temp-RH in the lung room with the AC on. This time of year its hot one day and cold the next with corresponding RH. I've been pondering the whole natural world thing while trying to maintain a good atmosphere for the plants. Has me thinking the RH and temps should rise and fall, same with the lights, over a range of time, as it happens in nature. Sometimes I feel like I'm working against the laws of nature.
 
Sometimes I mist them with rain water when the lights first come on. That usually brings the RH up to levels that require cycling of the fan.
 
I was following the pulse chart I posted earlier but now I'm using the charts the dimlux sent me. Each chart is different for compensation of the leaf temp. I increased the ppfd to 500 trying to raise the leaf temp by 2 or 3 deg. Hell I might kill this grow before I figure it all out. But I'll get it eventually.
 
I'm not sure if my humidifier is running in the dark or not. I do drop the humidity 5% and the temp 5° when the lights go out.
 
Hi @smoklahoma,
You are on a righteous but difficult path on VPD.
I obsess on that indicator of optimal conditions for healthy plant respiration but the conditions for really dialing it in are daunting.

I recently finished a grow room remodel and I am finally able to put VPD pretty much wherever I want it depending on the grown stage of my plants. I don't want to dissuade your pursuit, but here's the list of upgrades that made this possible.

- Grow Room circulation with separate intake for cool dry basement air and an external exhaust that pushes stale air outside.

- AC Infinity T8 fan with the controller 67 that displays VPD directly and allows fan triggers for both temp and RH. T8 is overkill but that allows it to run quietly at a lower speed to do the job.

- Portable air conditioner large enough to cool the room to around 70 all summer

- Oil-filled electric radiator capable of warming the room to around 70 all winter.

- Four gallon warm steam humidifier capable of increasing RH up to 65% all winter. Steam is way better for our cold dry winters, check the Optimus line.

- A fairly well sealed and insulated grow room, a little leaky but good enough for all those devices to do their job.

- Last but not least, an electrical upgrade to provide 35 amp service via two circuits connected to a standby emergency generator. Losing power now and again is a "Feature" of New England Winters.

So, my advice is that VPD control is worth the effort but you should be realistic about what you are getting into.

Cheers,
-Grouchy
PS, Oh, this project also cost me a cross-my-heart pinky-promise with my Saintly Spouse that includes a moratorium on spending!!!
 
Last edited:
Yea I use a temp gun as well to check leaves, once you know your set up the leaf temp offset seems to stay about the same. I just printed the relevant chart and stuck it on the shelf next to my tent for quick reference of temp and RH readings. Ac infinity only tells you room VPD I believe , as it has no offset
 
Yes my dehumidifier will run on lights off to lower RH.
If only it could anticipate the spike when the lights go out
 
You must log in or register to reply here.
Back
Top