Avering
Well-Known Member
Thanks man
Ac Infinity Humidifier
- Thread starter Avering
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Gsplover11
Well-Known Member
Set to auto,set rh to 50ish% done
Gsplover11
Well-Known Member
Literally just did it with mine,controller comes wednesday,gotta hook up my inline fan,humidifier,oscillating fans and the heater.
Amazing build quality onthese products.im really impressed
Amazing build quality onthese products.im really impressed
It looks like the sensor for the humidifier is on the back wall. The RH there is different than the RH for the plant. I always hang the sensor so that it's near the plant.
Unless you flip them very young, two well tended plants will fill a 2' x 3'.
This is one "well tended" plant in a 2' x 4'. The sensor is moved out of the way for the photo.
Note the sensor in the foreground.
Re which sensor - the sensor in the AC Infinity humidifier is most likely the more accurate.
In addition to the AC Infinity sensor, I've used el cheapos, an AcuRite Pro Accuracy hygrometer, an Inkbird RH controller, a Pulse One, and a Pulse Zero. When I calibrate them (salt test + a 75% Boveda calibration "kit") the AC Infinity was accurate out of the box to a few tenths of a percent,
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Avering
Well-Known Member
Thank you! That plant looks great! Im gonna go ahead and move the sensor as close as I can to the middle of the plants
I'd hang it "just above" (not very precise) the canopy. Leaves on the plant are constantly giving off moisture so the RH at the canopy level will tend to be higher than say, 6" or a foot above the canopy.
VPD is helpful but it's just a tool. The big issue is that if it's high you can change dilute the nute mix a little to avoid issues. On the other end, if it's low (high RH) that's when bud rot sets in so you want to make sure to stay away from that.
Avering
Well-Known Member
Thank you, it’s been high for me all grow but that’s cause I had wet towels hanging around. Id been looking around at posts about how people grow in very low rh (10-20) and they say they still grow great bud. Not sure how it would affect my plants but I strive to make the conditions the best I can. Why do you dilute the mix with low rh?
VPD is a number that describes the vapor pressure deficit between the plant and the air in the tent. A leaf is, in some ways, a bag of water so when the temp is high or the RH is low or a combination of those two, the difference between the bag of water (leaf) and the warm and/or dry air will be high. That's why it's called vapor pressure defecit.
There's always some level of difference in vapor pressure but plants in veg grow well when VPD is 1.0 (the units of VPD aren't important). The formula for your nutrients is based on having a VPD of 1. If VPD is, say, 1.2, which is the low end of where cannabis should be in flower, the vapor pressure deficit is 20% higher than 1.0 so 20% more water is transpired by the plant (than it would be at VPD of 1.0)
Since 20% more water is being sent out, 20% more water has to be brought in. If your nutrient strength is the same for a VPD of 1.2 as it was for 1.0, you're going to get…20% of the nutrients in the plant.
The goal of providing nutrients is to provide the 16 chemicals that are needed for the plant to reach its genetic potential and to provide those chemicals at the sufficiency range. If there are insufficient nutrients or excess nutrients, the plant will be negatively impacted. If the VPD is X% higher, transpiration goes up as does nutrient intake and the levels of chemicals in the plant start toward being in the toxicity range.
This isn't to say that you have to change your nutrient strength when VPD jumps up a little. The issue comes up if your VPD goes to a higher level and stays there because, in that case, we know that the increase in transpiration will tend to cause nutrient issues. There are a lot of variables (I'll be the first to admit I have some understanding of just a few of them) which is why I use the word "tend".
Two things - in watching videos by Bruce Bugbee and in reading through postings on scienceinhydroponics.com (the guy who runs the site is a PhD in chemistry and is the author of HydroBuddy) both authors state that a large percentage of nutrient issues are caused by VPD being out of whack. I don't recall Bugbee giving a number but Fernandez put it at over 50% and that makes a lot of sense to me because unless you mix your nutes wrong, there aren't a lot of other ways for things to go sideways. Oh, I've attached yet another graphic that lists the parameters of the grow environment. It's come in handy more than once.
Second, when I see a grow that's having problems with nutrients, I'll ask the grower about temperature and RH values and the answers are frequently values that put VPD well over 1.5, which is the very high end for flower.
Avering
Well-Known Member
Thank you. I have had issues in the past when my rh was low. Keeping it up around 80% now with my temps being around 88 in the tent and my plants look much happier. I have the window open and a big fan blowing air around in the room, in the direction of my veg closet. So, with lower vpd, they are able to make more use of the nutrients? Most people from what I have seen here talk about a higher vpd in flower is best for them. but some have mentioned that with proper ventilation and airflow, they are able to go through flower with 80s to 90 temp and 70-80 rh
88° and 80%?! Something's off there. That's a little moist for germination.
VPD works off of leaf surface temperature and ambient temp + ambient RH.
Check this screenshot:
At 88 and 80, that's hot and muggy. 88's a little higher than you want but RH, for veg, should be in the mid to low 70's at that temperature.