completely different and doesn’t preserve the terp, and takes a longer time compare to a freeze dryer. I tried once with my first outdoor grow of some Fruity Pebbles and is pretty bad. Also had some mold issue on some buds but these were clean and still came out bad
So I did a little experiment. Did one batch 35F shelf limit (which gets as high as 42F on the tray heaters), 12 hours final dry. The machine automatically goes into small batch mode (25 cycles) because vapor pressure does not ever reach the default 500/600 mtorr annealing settings. Even after 12 hours the center of the buds still had some moisture which caused the buds to go from crispy to fairly moist all on their own. By the time I realized it, it was too late the machine had already been defrosted and I don't think there was enough moisture in the buds to freeze and run it through again. I think the stems inside the buds resist sublimation at that shelf temp. Almost no smell in the defrost water and only slight odor in the machine. Im going to have to cure those the standard way I think.
Second batch, 40F shelf limit (which gets as high as 50F), 14 hours final dry. Buds came out COMPLETELY dried out and I noticed more terp smell in the water and in the machine after defrosting. So, I think next time Im going to go right in the middle. 37F shelf limit, 13 hours final dry, or maybe do 35F again with an even longer final dry (18 hours?)
Both of these batches had zero grassy chlorophyll smells at all. The first batch is super pungent, and jarred with bovedas the 2nd batch is starting to restore its smell as the bovedas do their work.
So to recap, I think 35F is the sweet spot if you want to retain as much terpene content as possible in the final product, just a longer final dry time is needed to squeeze out the core moisture. As shelf temperature rises, a noticeable amount of terpene smell is present in the machine and the defrost water, so there is terpene loss, but the buds dry much faster. In my case too fast.
Just thought I would post this up in case anyone else has a freeze dryer and thought about doing low shelf temp drying.