Dialing-in an UHL grow chamber

Gadzooks

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I recently completed a 7cu ft chest freezer conversion into a UHL grow chamber and wanted to get some tips from those of you that have successfully grown RHH and N. Villosa. Ranges of temperatures, hours for the temperature cycles, light-hours, average RH, and anything else you can think of. Additionally, a list of plants that would live together under these conditions couldn't hurt either.
 

Gadzooks

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Well, I should at least give you a primer on the current configuration. I modeled it based on a video from our friend Brad and an article authored by Dr. Jeff Shafer. I am using a PetsPioneer temperature and humidity controller. Which provides 3 device controlled surge protector. The light is on one of the controlled receptacles and provides the heat input in addition to the 12hr grow period from 0800-2000. The humidity is controlled via a 25CFM fan that turns on at 70% and turns off at 80%RH. The freezer is cycled to maintain day-time temperatures at 70-72F and night-time at 40-43F. The light fixture is a common hardware-store RBW 32w LED growlight. I added some mass in the form of a sphagnum propogating tray and some freezer packs (not shown) to arrest changes in temperature from one state to the other. The freezer is much better at sinking heat and so the drop from one range to the other occurs in 1hr. Anyone got tried and true graphs of relationships of temperature, humidity, and light cycles? If so, I'd love to benefit from your experience.
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Gadzooks

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Soo it's been a few weeks. I've been reading quite a bit. Looks like a 30F swing is sufficient for all UHLers and that it's the drop not the temperature that is significant. Additionally, a UHL grow chamber is not needed for young plants. I have one so I intend to use it to figure out what works.

During all the research and trials, I flipped the spectrum to blue-white at 53.3µmol/s and expertly scorched all the tips on the HI sphagnum. I have been propogating it from an orchid stowaway for the past year.
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I removed half the sphag and placed back where it was happiest and the rest on the bottom of the chamber. I flipped the spectrum to red-white at 44.9µmol/s
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Also, for some reason my temps where out of spec low. So I moved the band up because I was getting subzero indications on the sensor. I also set up the fan to blow straight onto the sphagnum in the bottom of the freezer. As a result, humidity quickly picks up when below the setpoint. The temp rise is solely the LED light fixture's contribution over ambient temperature and seems to plateau around 75F. Fan only really kicks on during the cool-down as the humidity plummets. You can see the cycles during the night.
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Concerns going forward are:
Is my light too close? It's 8-Inch from the plants crown. I have lids drying up, but it could just be shock from shipping. I never refilled the pitchers.
Is my humidity too high? It's seems fine, but it literally rains every day from the condensation on the cover.
Should I sacrifice humidity stability for increased airflow by turning to airflow back onto the plants? Maybe add a constant fan to run during lights-on.

I don't want to shift too many things at once, but I'll write my observations as conditions change.
 

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Gadzooks

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2months of growing Nepenthes Villosa. (that's like a single day in the life of... so no great accomplishment yet) I figured there might be something of interest that I could share.

I have made some adjustments:
Days are 70-72F, nights are 52-54F (i have settled on this range because i intend to also grow with N. Diabolica and N. Aristolochioides.) N. Diabolica has the narrowest altitude distribution according to multiple articles; temperature and RH have been established to favor the Red Hairy Hamata. N. Villosa is distributed across a much larger elevation than the 2.2-2.3km reported for RHH.

I have not been able to find sequenced shots of a glacial grower as it adapts from shipping shock and new growing conditions. This is probably because no one wants to show off their skills as a grower with a sad specimen. Worse yet, have to openly admit a loss 😬.

I do worry about the reddening and the leaf size reduction, but I try not to make too many adjustments chasing the plant as it aclimates😅
I do recognize that if given too much light, and the plany doesn't have a pitcher to provide a mechanism for nutrients uptake, I may have to apply foliar fertilizer or risk it's decline.

I keep the light 8" from the crown and water twice a week.

Looking for some feedback from growers of the three species mentioned.

I will post update for the chamber parameters as I was able to stabilize temperature lows and fix humidity transients during night.
 

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Gadzooks

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I opened the thread asking for a list...
It should be stated, that no one can really recommend what you should attempt to grow.

If you love that particular plant, then you will research the care requirements and adapt it to the best environment you can create for it. You will also find that you have more than enough money to offset incidental costs. I see that many people post looking for some kind of deal on a species plant or a rare hybrid. There is no currency that is more intrinsically valuable than that of living things. The best "deal" is when the plant you want is available for purchase. Most people have a $1000 phone that will be "dead" in a couple years. Why not cohabitate with an other earthling of a different Kingdom. That might be a story worth telling the grandchildren.
 

Gadzooks

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Now that I am off my soapbox, I have made my list.

Obtained:
Nepenthes Aristolochioides
Nepenthes Diabolica
Nepenthes Aristolochioides x Diabolica
Nepenthes Villosa
Nepenthes Rajah
Nepenthes Burbidgeae
Nepenthes Mollis
Nepenthes Nebularum
Nepenthes Miranda
Nepenthes Alata
Nepenthes Ventricosa
Nepenthes Bill Bailey
Nepenthes Suki
Nepenthes Diana

Booked:
Nepenthes Singalana
Nepenthes Klossii
Nepenthes Attenboroughii
Nepenthes Ovata
Nepenthes Mapuluensis
Nepenthes Bongso
Nepenthes Hamata x Edwardsiana
Nepenthes Ampullaria

Sought:
Nepenthes Edwardsiana
Nepenthes Hamata
Nepenthes Macrophylla
Nepenthes Lowii
Nepenthes Trusmadiensis
Nepenthes Rafflesiana

👐😰They are not all going into the 7cuft HL grow chamber 😄.
 

Gadzooks

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So after a month of closed chamber ops, I noticed that the acrylic sheet was warping due to what I assume was differential temperature and the light fixture resting on it. This pulled up the corners and I could feel air flowing out. I have flipped the .177in sheet a few times and it just slowly "melts" the other direction.

For anyone wondering how much mass buffers the freezers ability to drop air temp; I put 3 gallon jugs, the air temp still drops faster than it can heat the water. So I promptly took out the water to save room for actual growers because the added mass is negligible.

I had issues with temps dropping below setpoint. I attempted to account for this with the thermostat setpoint (and mass), but the time that the compressor ran and the humidity kicking on the fan (which improved cooling) made this very difficult.

I realized that if the thermostat is not touching the cooler surface (wall), then it is monitoring air temp. That means that the walls have subcooled below the required temp and have begun to cool the air. If the thermostat kicks off now the air temperature will continue to drop until it equalizes with the wall. In short make your thermostat read the coolest surface and you won't ever have temperature overshoot.

By removing the useless gallons of water and having the Tstat monitoring the coldest surface, I was able to arrest the temperature drop from a single compressor cycle to almost a 4hr transition to night-time setting.

The graph shows a near-wall measurement and a central measurement.
 

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Gadzooks

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Because that wasn't enough...

I needed to fix humidity. So I decided to install vent hoses between the grow chamber and my intermediate grow-tent. I did this with a 4in hole-cutter and I used some 1-way dampers and bathroom duct hose.

So, should I draw suction on the chamber or the tent?

I first tried blowing into the chamber. It was at this point I knew, I needed a gasket and a thicker acrylic sheet. It was functional, but I really wanted a nice 60F(getting there) in the tent and I wasn't going to get that without a closed loop.

So I outfitted it with a new sheet (about twice as thick), added a cable gland (for the fan, tstat, term, and hydrometer), and a foam rubber gasket.

The results were excellent. Great humidity response and controlled temperature drop into the night-time. How, I added another controller to cycle the duct fan based on the grow tent's temperature coming out of the HL chamber. Still working out the losses to get the tent (which is much larger volume) down to 60F.
 

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Seeing projects like this is always nice, if I had the ambition I'd love to make one myself. I'll also be waiting updates excitedly
 

Gadzooks

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Thanks! maybe I'll put together a Bill o' Materials for those out there looking to learn from my mistakes.
 

Gadzooks

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Should have mentioned that the fan that cycles to control the growtent temp reduction is a 50cfm fan. I Added 195cfm inline fan to draw from the chamber at the same time (in parallel). This was to draw a vacuum on the chamber and better seat the acrylic cover by compressing the gasket. I was looking to have better performance overall.

The results are in. Total failure to regulate temperature. The HL grow chamber (functioning as the cooling plenum) was not sufficiently mixing the incoming air. As a result the out-going air to the intermediate tent, as measured by the thermostat, was never met and the fan never kicked off which would have allowed the freezer to hit the desired temperature. There was insufficient mixing in the freezer and so the intermediate grow tent was basically on recirculation with slowly lowering temperatures due to ambient losses (hoses and tent walls) throughout the night.

Options are:
Add baffles and fins to increase air mixing in the grow chamber which also reduces overall airflow by creating a tortuous path
-or-
Redirect incoming air to the wall that has the cooling element and the thermostatic control sensor.

Both put more load onto the freezer and a significant amount of air volume larger than designed. I do recognize that the volume of air is less mass than the solid food items it is designed to cool. I don't think the compressor however, is designed for a continuous duty cycle.

I don't want to cause multiple large-temperature transients throughout the night, I'll stick to gradually undesirable for a day. I'm reverting back to giving the plants a few days of ideal conditions to recover before the next iteration.
 

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