Portable air con for drying tent

So I've got 4 plants drying in a 90cmx90cmx180cm (3x3x6) ac infinity tent, I've got an 8000btu portable air con in there, the air con exhaust hose goes through the duct port and into a huuuuuge carbon filter by a window. The intake for the tent is a duct going Through a hole in my ceiling and through another huge carbon filter in the loft.

I'm managing to keep my temps consistent at 16'c all day and night but the problem I'm having is with humidity. At night I can maintain 60-65% which is normal for this stage (only chopped 3 nights ago) but through the day the humidity is going upto 80% and I can't for the life of me understand why. It's honestly got me bamboozled.

Any insight? Anyone with any advice what so ever?

if I can't get this sorted today I'm gonna sacrifice the temperature for stable humidity and dry in a tent in my flower room in the hope that the 55% intake air will stop any mold problems

I've just bought another small tent that I can use as an intake where I'll place the air con and a dehumidifier to cool and dry the intake air

Obviously the source air from the loft is of high rh, I just can't understand why it's manageable during the night when source air temp is lower but not during the day when source air temp is higher, surely higher temp should mean lower rh, plus the compressor should be lowering the humidity to even more through the day as it works more to cool the warmer source air

Whats the loft like that your intake is pulling from? Heat and humidity rise so maybe it’s that. During the day the temps up there are hotter i guess??HIgher temps doesn’t automatically mean lower rh. maybe just intake from more stable conditions? Daytime loft temp and rh could be just higher than the capacity of the dehumidification capabilities of the ac unit ?

Blue brother said:

Obviously the source air from the loft is of high rh, I just can't understand why it's manageable during the night when source air temp is lower but not during the day when source air temp is higher, surely higher temp should mean lower rh, plus the compressor should be lowering the humidity to even more through the day as it works more to cool the warmer source air

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higher temps don't necessarily mean lower rh. Usually, where i live, the colder the air, the lower the humidity is. Summertime is the opposite.

Source air at night has lower temperature and needs heated more, having a lower temperature than daytime means it can't hold as much moisture, then on top it's getting heated more than daytime air lowering the rh% further.

If you think about the amount of dew in the grass it's a lot of water less to deal with?

Basic numbers are as follows.
Air pulled into a tent needs to have about a 10-20% RH lower then what your target is. If your lung room is 45% RH all the duct pull in the world will not get you 45% RH in the tent.
Get a mobile temp and RH sensor and look for a source of lower RH in the house or like you are doing make a lower RH source with a AC unit or dehue. The Lung tent could work but right now you have either a math problem or you need to set it up and see how it works.
My guess is that the low btu will not lower the RH enough without lowering your tent temp also due to the amount of duct pull needed to move the air in the tent. A dehumidifier will dry the air without substantially lowering the temp.
I love the challenge of environmental setup but some aspects of growing can be very expensive to fix built in problems like the loft being the natural point where humidity gathers at night due to temp inversion from day and the natural movement of heat to go up.
Even in a room you can have a 10% difference in RH from above the tent to floor level. That's why so many tents have the bottom vents with built in insect screens.

Ok so I tried to intake from my flower room 55% but I'm still sat around 65-70% through the day, I set up the other tent and used it as a lung and I've had that set up all day but to keep the temp down at 16c I've had to exhaust the tent so fast humidity dropped to 50. I'm done chasing my tail, I've bleached and alchohol cleaned the wine fridge conversion I built years ago and it's sat airing out as we speak, the plant matter has lost approx 50% of its size so far and if I remember correctly I used to dry about 16 oz in the wine fridge. So I'm guessing I could fit what will dry to be about 30oz in there right now.

either tonight or in the morning I'll be filling the wine fridge with bucked down buds out the drying tent. And retiring the drying tent/ portable air con combo.

for the next harvest I'm gonna build another couple wine fridges out as I can only get the 18 bottle ones atm

the portable air con will come in handy cos I can use it to cool the tent I keep the wine fridge in which allows the wine fridge to get all the way down to 12'c

in hindsight I should've just bought and built the wine fridges before this harvest but I didn't wanna have 3 of them and instead opted for the air con/tent combo

thanks for everyone's help, I'll post back here once I've got my wine fridge filled