My 90L temperature controlled terrarium/orchidarium. Description and questions.

[itilien]

Let me present you my terrarium/orchidarium and ask few questions.



Video:
You?re Temporarily Blocked

It is 90 L (w51 x h56 cm ), closed, insulated and temperature controlled tank. It has unusual shape because it is placed in a corner.
The sides and the bottom of the tank are insulated with 5cm XPS foam sheets, and behind one of the back walls is attached a XPS box . The connection between them is made by 2 square holes in the glass. A 80mm fan rotates the air through the box.

Inside the box is a cylindrical metal tank with volume 1.6L which is filled with water. This tank is part of the cooling system, which is a compressor based and taken from water dispenser. The air passes around the metal tank and cools down. The condensation that appear on its metal wall collect to the bottom of the XPS box, where it can be used for fogging (currently I don't use it, because there are some brass parts in there, which leak small quantity of copper salts in the water and I'm not sure if they can affect the plants and mosses). There is also a drainage in the wall to keep the water at constant level.


fog video:
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The compressor itself is outside the box.
Inside the box there is also a small car light bulb which is used to warm up the air if needed.

The top of the terrarium is double glass for better thermal insulation.

4 LED lights are placed 12cm above the top glass. 2 of them are 1050 lumens, other two 400. These are 6500K, high color rendering index bulbs (CRI>95), which I have disassembled. I took out the PCBs and the metal plates with the leds. The led plates are glued with thermal silicone to a big aluminum sheet. This has two purposes - first to cool them better, thus increase their live, and second - in this way they take much less vertical space.

Misting is done by a 4 nozzles placed in the center just above the front glass. Water is pumped by a 12V, 4.3L/min, 85psi pump.

video:
You?re Temporarily Blocked

Ventilation is done by the fan which rotates the air through the cooling box and a 40mm fan which is place among the nozzles. This fan is stopped during the misting. There is no ventilation to the outside air (only when I open it).

The whole system is controlled by arduino based device and it can be configured as I want, but there are some limitations because of the thermal inertia and the power of the compressor. The maximum I can get is about 10 degrees below room temperature and 2 more degrees if I place XPS sheet over the front window at night. The hottest temperature that I have measured in my room was 29.5 degrees during the hottest time in the end of July/beginning of August, so this mean about 17-18 degrees minimum temp inside the tank. Hopefully this hot periods are not very long and the usual summer room temperature is between 25 and 27 degrees.

Now for the current parameters of the environment.

Temperatures are kept between 16.5 C minimum night and 22.5 C maximum day, but I plan to increase the day temperature to 24C.

The day is 14 hours long. The night cooling regime starts 2 hours and a half before the lights turn off and ends 1 hour and a half before they are turned on. During the day the cooling is running only if room temp is above 23 degrees. Thermally the system is quite inert because of all the thermal mass inside it (glass, 8-9 liters of water (there is a water below the false bottom too), soil, roots), so the temperature changes are quite slow. Daily misted with RO for 40 seconds 2 hours after the lights are on.

Humidity is above 90% the whole time.

At the moment the tank is 3 months old and there are 5 orchids inside - Specklinia (Pleurothallis) corniculata and grobyi (but leaves looks more like picta), Aerangis Calantha, Schoenorchis tixieri and Psygmorchis pusilla.
Also there are few more waiting to be installed:
Specklinia (Pleurothallis) lateritia,
Masdevalia nidifica (it seems a little big for this tank),
Haraela retrocala,
Trisetella triglochin,
Lepanthes guatemalensis,
Lepanthes calodiction,
Lepanthes telipogoniflora,
Lepanthes montezumae x posthon

Some others planned for buying:
Stelis hirtella
Trisetella hoeijeri
Pleurothallis brighamii

And now the questions. Do you think that I need to lower the humidity?
Are some of the above mentioned orchids not appropriate for this setup or conditions.
Do I need to change the temperatures?
Do I need to put the roots of any of those orchids in moss (live moss or dead sphagnum) at this humidity level?
Any proposals where to place the orchids that are still not in the tank?
Any other advice is welcome!

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[Ray]

That is beautiful!

[Roberta]

That is a beautiful setup!
With regard to humidity, 90% I think is too high for all the time. During the day, I'd suggest more like 70-80%. You can let it go higher overnight, that's what happens in nature when the temperature drops. You might also want to reduce the "day" to 12 hours... again, that is what happens in nature near the equator - equal days and nights.

[itilien]

Thank you very much

Regarding the humidity - I have some ideas how to lower it in a controlled way, but it should be done only during the day and not in the hottest days, because exchanging air means thermal loss and the cooling system won't be able to keep the needed temperatures. Also when the cooling runs, the humidity is little bit lower, because the vapors condense over the metal tank in the box. The other problem is that humidity sensors are not reliable at high RH levels.

By the way, the mosses (temperate) like the current conditions.

I will shorten the day, at least this is easy.

[Roberta]

I would not worry too much about humidity going a bit low during the day. Temperature is the more important parameter if you need to choose.

[itilien]

the problem is opposite. Let say in the room is 29 degrees and I want to have 23 inside the tank. If I want to get lower RH, I need to exchange some of the air with warmer outside air. So the cooling will need to work more. It will be a matter of experiments to see how much air will need to be exchanged and what temperatures can be achieved.
But it is sure that if I want to get down to 17 degrees in the night of such warm day, I won't be able to exchange any air, and the RH will have to stay high.