VPD

[OGeMann]

Waiting for the seeds to get a longer tap root while germinating going on 3 days. I have been following VPD for some of 3-4 years now. My question is once they have their set of leaves and then the true leaves I follow VPD at 0.6-1.0 is it better to have the range between those # or a target # ??
My VPD is as follow:
seedling to early veg: 0.6-1.0
Lt veg to Ea Flo: 0.8-1.2
Mid to Lt Flo: 1.2-1.6
If any of you guys have any recommendations I'm open to any....
.....Happy Growing.....

 

[jmrl]

Waiting for the seeds to get a longer tap root while germinating going on 3 days. I have been following VPD for some of 3-4 years now. My question is once they have their set of leaves and then the true leaves I follow VPD at 0.6-1.0 is it better to have the range between those # or a target # ??
My VPD is as follow:
seedling to early veg: 0.6-1.0
Lt veg to Ea Flo: 0.8-1.2
Mid to Lt Flo: 1.2-1.6
If any of you guys have any recommendations I'm open to any....
.....Happy Growing.....

If you just keep your RH% in Check 70%-50% During Veg for now and try to keep it below 85 Temp Wise. I tried to follow the VPD around 1.0 also, during VEG It was easy. Afterward, not so much.

 

[Trump]

Waiting for the seeds to get a longer tap root while germinating going on 3 days. I have been following VPD for some of 3-4 years now. My question is once they have their set of leaves and then the true leaves I follow VPD at 0.6-1.0 is it better to have the range between those # or a target # ??
My VPD is as follow:
seedling to early veg: 0.6-1.0
Lt veg to Ea Flo: 0.8-1.2
Mid to Lt Flo: 1.2-1.6
If any of you guys have any recommendations I'm open to any....
.....Happy Growing.....

How are you calculating your VPD? Are you including leaf temperature in the equation? VPD is not as accurate unless you use leaf temperature as part of your data.

Air temp isn't as important as leaf temp. Leaves photosynthesize most efficiently at around 76° - 78° leaf temp.

Go to the Dimlux site and download their VPD charts. They have different ones depending on the differential between air and leaf temp. They also have a handy calculator for you to figure out what your present VPD is.

Generally, I've found in seedling to early veg keeping RH in the 60% - 70% and temps in the 75° - 80° range best. Lt veg to late flower 55% - 65% RH/78° - 82°. Late flower to harvest 45% - 55% RH/75° - 78°.

 

[jmrl]

How are you calculating your VPD? Are you including leaf temperature in the equation? VPD is not as accurate unless you use leaf temperature as part of your data.

Air temp isn't as important as leaf temp. Leaves photosynthesize most efficiently at around 76° - 78° leaf temp.

Go to the Dimlux site and download their VPD charts. They have different ones depending on the differential between air and leaf temp. They also have a handy calculator for you to figure out what your present VPD is.

Generally, I've found in seedling to early veg keeping RH in the 60% - 70% and temps in the 75° - 80° range best. Lt veg to late flower 55% - 65% RH/78° - 82°. Late flower to harvest 45% - 55% RH/75° - 78°.

You have the exact ratios I use my man. Very good numbers to go by here. Except my temp is a bit higher for me during flowering because I use a wood stove for heat.

 

[Trump]

You have the exact ratios I use my man. Very good numbers to go by here. Except my temp is a bit higher for me during flowering because I use a wood stove for heat.

Perfect. Higher flower temps aren't an issue as long as you don't get into the 85° - 90° range for an extended period of time.

I'm getting to the end of my current grow so I've been ramping down the light intensity and temperature. I use DLI(Daily Light Integral) as a guide to how much light at whatever stage the plant is in. Makes it so much easier to get the correct exposure when they need it.

Check out the 2 ScrOG journals I got going. They're in the sig below. It shows all the stats over the course of the grow.

 

[OGeMann]

How are you calculating your VPD? Are you including leaf temperature in the equation? VPD is not as accurate unless you use leaf temperature as part of your data.

Air temp isn't as important as leaf temp. Leaves photosynthesize most efficiently at around 76° - 78° leaf temp.

Go to the Dimlux site and download their VPD charts. They have different ones depending on the differential between air and leaf temp. They also have a handy calculator for you to figure out what your present VPD is.

Generally, I've found in seedling to early veg keeping RH in the 60% - 70% and temps in the 75° - 80° range best. Lt veg to late flower 55% - 65% RH/78° - 82°. Late flower to harvest 45% - 55% RH/75° - 78°.

yes I'm calculating leaf temps, I have a Pulse One and its pretty accrete, thats the site I use been using that site for VPD since I started using it

 

[Delps8]

Waiting for the seeds to get a longer tap root while germinating going on 3 days. I have been following VPD for some of 3-4 years now. My question is once they have their set of leaves and then the true leaves I follow VPD at 0.6-1.0 is it better to have the range between those # or a target # ??
My VPD is as follow:
seedling to early veg: 0.6-1.0
Lt veg to Ea Flo: 0.8-1.2
Mid to Lt Flo: 1.2-1.6
If any of you guys have any recommendations I'm open to any....
.....Happy Growing.....

The only time I use a range of VPD's is in flower. Other than that, I use 0.8 for germination and seedling, 1.0 for veg, and then 1.2-1.4 in flower. Those are the values I used when I got my PulseOne and I use the same values now that I've migrated to the AC Ininity Controller 69.

Having a range of VPD values strikes me as a bit strange because VPD itself describes a range a values. I couldn't argue that a VPD between 0.8 and 1.2 could be "optimal" in late veg to early flower because that means that optimal temp+RH could range from 70° and 65% to 70° and 45% and 86° and 75% to 86° and 65% RH. Those are very different grow environments to all fit under the "optimal" label.

ATM, my grow is on day 30 and it's at 1.0

 

[OGeMann]

Perfect. Higher flower temps aren't an issue as long as you don't get into the 85° - 90° range for an extended period of time.

I'm getting to the end of my current grow so I've been ramping down the light intensity and temperature. I use DLI(Daily Light Integral) as a guide to how much light at whatever stage the plant is in. Makes it so much easier to get the correct exposure when they need it.

Check out the 2 ScrOG journals I got going. They're in the sig below. It shows all the stats over the course of the grow.

I was just thinking the same thing about DLI and you are right it is easier to read DLI then to read PAR, I know they go hand to hand but getting that DLI the plant wants is alot easier to follow..good call....I checked out your journal "great job". I actually enjoy scrogging and the one I'm on will be scrog.

 

[OGeMann]

The only time I use a range of VPD's is in flower. Other than that, I use 0.8 for germination and seedling, 1.0 for veg, and then 1.2-1.4 in flower. Those are the values I used when I got my PulseOne and I use the same values now that I've migrated to the AC Ininity Controller 69.

Having a range of VPD values strikes me as a bit strange because VPD itself describes a range a values. I couldn't argue that a VPD between 0.8 and 1.2 could be "optimal" in late veg to early flower because that means that optimal temp+RH could range from 70° and 65% to 70° and 45% and 86° and 75% to 86° and 65% RH. Those are very different grow environments to all fit under the "optimal" label.

ATM, my grow is on day 30 and it's at 1.0

That's where I have problems at is in "flower", I fully agree with you on some of those values that to a grower you dont want high humidity of about 60%-70% but I guess with the right temps you probably get away with, but me myself I will not take that chance. May I ask, I have the fist generation of the AC controller ...non wi-fi one running my exhaust running great for being 5-6 years old.. I have a Pulse One, how is the comparison of the two ?
If you dont mind i will foll your journal

 

[Delps8]

That's where I have problems at is in "flower", I fully agree with you on some of those values that to a grower you dont want high humidity of about 60%-70% but I guess with the right temps you probably get away with, but me myself I will not take that chance.

I'm with you there. Everything I've read about VPD supports the idea of dropping RH as the plant matures. I have no reason to not use low RH as the plant matures.

May I ask, I have the fist generation of the AC controller ...non wi-fi one running my exhaust running great for being 5-6 years old.. I have a Pulse One, how is the comparison of the two ?
If you dont mind i will foll your journal

Re. following my journal - absolutely. After a few false starts, my Spring 2024 grow is in process and I'll start a journal for it tomorrow.

Re. our Pulses — I moved from the PulseOne to the Controller 69 ("C69") and other equipment from AC Infinity. The main driver for the change was that AC Infinity released a line of humidifiers that worked with the C69. I placed an order as soon as they were available and retired my Pulse, two Inkbirds, and a "reptile" humidifier. Here's why…

The PulseOne suited my needs but a personal grower with one 2' x 4' tent was not the target market for Pulse (check out their new products and you'll see where they think the money is). It was great to have the info from the Pulse but it has no way to control anything so I would frequently check the VPD reading on the Pulse and then fiddle with the RH setting on the Inkbird to get the humidifier to run. Yup, I checked my Pulse app many times per day for an entire grow to keep VPD in range. A huge time sink but it got the job done - I think that was the grow that came in at >750gm/m2 but can't be sure.

It's a completely different story with the C69. It's set and forget. I set the VPD and have alerts for VPD being out of range. I can check the app whenever feel the need but there's no need to — the C69 just cranks along, turning the Hugh on and off, as needed.

I didn't like the idea of having spent $199 + $50 per Inkbird + $40 for the humidifier and then spend $100 for the C69 + $50 for a new Hugh but it wasn't much of a decision in reality - for $150, I never have to screw with setting RH again. And I also get a well written app that will allow me to control three other devices in my tent from anywhere in the world. All for $150.

 

[OGeMann]

I'm with you there. Everything I've read about VPD supports the idea of dropping RH as the plant matures. I have no reason to not use low RH as the plant matures.


Re. following my journal - absolutely. After a few false starts, my Spring 2024 grow is in process and I'll start a journal for it tomorrow.

Re. our Pulses — I moved from the PulseOne to the Controller 69 ("C69") and other equipment from AC Infinity. The main driver for the change was that AC Infinity released a line of humidifiers that worked with the C69. I placed an order as soon as they were available and retired my Pulse, two Inkbirds, and a "reptile" humidifier. Here's why…

The PulseOne suited my needs but a personal grower with one 2' x 4' tent was not the target market for Pulse (check out their new products and you'll see where they think the money is). It was great to have the info from the Pulse but it has no way to control anything so I would frequently check the VPD reading on the Pulse and then fiddle with the RH setting on the Inkbird to get the humidifier to run. Yup, I checked my Pulse app many times per day for an entire grow to keep VPD in range. A huge time sink but it got the job done - I think that was the grow that came in at >750gm/m2 but can't be sure.

It's a completely different story with the C69. It's set and forget. I set the VPD and have alerts for VPD being out of range. I can check the app whenever feel the need but there's no need to — the C69 just cranks along, turning the Hugh on and off, as needed.

I didn't like the idea of having spent $199 + $50 per Inkbird + $40 for the humidifier and then spend $100 for the C69 + $50 for a new Hugh but it wasn't much of a decision in reality - for $150, I never have to screw with setting RH again. And I also get a well written app that will allow me to control three other devices in my tent from anywhere in the world. All for $150.

well that sounds like what I do is constantly checking the pulse, I had alarms set but had to shut them off it was making me go crazy . I also have inkbird heat/hum controllers too. I might have to check AC out, would the new 69 controller work with my AC infinity fan??
thanks for the information because I personally like data...

 

[Delps8]

well that sounds like what I do is constantly checking the pulse, I had alarms set but had to shut them off it was making me go crazy . I also have inkbird heat/hum controllers too. I might have to check AC out, would the new 69 controller work with my AC infinity fan??

Run, don't walk. Seriously.

I would expect that the fan will work with the C69 but check their web site. The key issue is being "UIS" compatible where UIS is the interface that they've created for all of their devices.

The C69 comes in different "trim levels". I went with the Pro which is BT + WiFi and four devices. The Pro Plus handles eight devices.

thanks for the information because I personally like data...

Same here. I've been writing business software for 30+ years. "data" is even in the name of my company.

[time passes]

Just read a few postings in one of your journals. The orange printing on your Pulse is faded - you have had that for a while!

 

[OGeMann]

Run, don't walk. Seriously.

I would expect that the fan will work with the C69 but check their web site. The key issue is being "UIS" compatible where UIS is the interface that they've created for all of their devices.

The C69 comes in different "trim levels". I went with the Pro which is BT + WiFi and four devices. The Pro Plus handles eight devices.


Same here. I've been writing business software for 30+ years. "data" is even in the name of my company.

[time passes]

Just read a few postings in one of your journals. The orange printing on your Pulse is faded - you have had that for a while!

Got it a month before the pulse pro came out, so yes it been like 5-6 years now

 

[Trump]

Run, don't walk. Seriously.

I would expect that the fan will work with the C69 but check their web site. The key issue is being "UIS" compatible where UIS is the interface that they've created for all of their devices.

The C69 comes in different "trim levels". I went with the Pro which is BT + WiFi and four devices. The Pro Plus handles eight devices.


Same here. I've been writing business software for 30+ years. "data" is even in the name of my company.

[time passes]

Just read a few postings in one of your journals. The orange printing on your Pulse is faded - you have had that for a while!

Agree. The ACI controllers make it easy to set it and forget it. I have the C67 bluetooth. I'd like to swap it out to the same BT+wifi. I won't need more than 4 device ports as the only thing I need to control are the exhaust fan and humidifier. The C67 only allows me to run the E fan and their oscillator fan. I currently use an ACI T3 for humidifier, but I have to run it independently until I can pick up a C69.

I would agree that there is an "optimal" number when it comes to VPD but I find ranges a more realistic way as temp and humidity swings happen throughout the grow. To hit that perfect number is not hard. To maintain it without it fluctuating is not as easy.

 

[Delps8]

Agree. The ACI controllers make it easy to set it and forget it. I have the C67 bluetooth. I'd like to swap it out to the same BT+wifi. I won't need more than 4 device ports as the only thing I need to control are the exhaust fan and humidifier. The C67 only allows me to run the E fan and their oscillator fan. I currently use an ACI T3 for humidifier, but I have to run it independently until I can pick up a C69.

Got it.

I would agree that there is an "optimal" number when it comes to VPD but I find ranges a more realistic way as temp and humidity swings happen throughout the grow. To hit that perfect number is not hard. To maintain it without it fluctuating is not as easy.

VPD is not a measure of temp and RH - it's a measure of a pressure difference between the water in a plant and the water in the air.

When we use a device like a VPD controller, the controller sets activates HVAC equipment to set the ambient temp + RH to values that allow the plant to transpire at the optimal rate.

If you were to use a range of VPD values, there would not be much of a reason to even use HVAC equipment in most situations because, one, you're not going to get optimal growth and, two, ambient temps and RH usually don't change so much that a grow can't be kept "in range".

With just a single number, the equipment in the grow environment will maintain the temperature and RH of the grow environment so that the plant can transpire well. Neither the temperature, by itself, nor the RH, by itself, are that important (in terms of VPD). When the C69 is running, it will increase RH as temperature increases and will drop it was temperature decreases. Check the attached screenshot and look for the combinations of values where VPD is 1.0.

At 68°, RH of 52% will result in a VPD of 1.0. Good to go. If the temperature increases to 85°, a brutal temperature swing but not out of the realm of the possible, the C69 will increase the RH to 70% to keep the vapor pressure differential at 1.0.

In this case, VPD can be kept in the "optimal" range by changing RH even in face of a temperature swing of almost 20°.

In the screenshot below, the temperature range is only 4° and the RH swing is < 5%. In this case, I'm using the C69 to control the humidifier (a T3 called "Hugh"). When the T3 is connected to the controller, it can be set to any integer value between 0-9. In my setup, the C69 runs Hugh for a few seconds every minute and VPD ranges from 0.9x to 1.1x.
In other grows, I've used a heater on port 4 to keep temps in the 70's and then Hugh runs on port 1 to control VPD. The C69 makes it really easy.

These screenshots show the AC Infinity app running on a MacBook Air.

When VPD exceeds 1.0, the C69 fires up Hugh.

 

[Delps8]

Got it a month before the pulse pro came out, so yes it been like 5-6 years now

Definitely got bang for your buck!

You'll love using the C69.