Suggestions for dry air conditioner

My 3D printer room has been engineered with multiple levels of containment along with air scrubbers and filters. For starters, I use an enclosure that has a filtering unit in it. I also have a sealed room with a dehumidifier. However, I am encountering problems with PLA printing where I am getting heat creep. The room gets pretty warm and it gets even warmer in the enclosure. I will need to design a filtered venting system to let cool air in for certain filaments like PLA. I also need to cool the room.

I have tried air conditioners but I find that they actually contribute to moisture and end up competing with the dehumidifier. My last air conditioner was a dual port portable a/c so it was pulling and exhausting with the outside but it is still blowing moisture into the room.

I bought my TAZ printers mostly for my seven year old son as I figured it is like having a personal library. Just like having books at his fingertips has helped him to be a precocious reader so too can 3D printers develop his engineering skills. But I am also going out of my way to make sure that his exposure to air born material is limited as much as it can be.

Does anyone have any suggestions to how I can get a dry air conditioning unit? Is there a keyword I need to search on? Can anyone recommended any specific units?

I would also like to hear how anyone else designed their containment or filtering systems for their rooms.


A/C Units (with coolant, not the water chilling effect thingies) in general have a drying efect to the air they are cooling down. This is because cold air can not hold as much water as warm air.
There are A/Cs that cool air coming from outside (i.e. window units) and others (i.e. split units) that “only” circulate the air in the room.
Split units usually have more of a drying efect over time as the same air gets pushed to the cooler several times.

Please be Aware: drying with A/C only works if the unit is cooling the air.

All the Best

I think i am hearing you say that there are at least 2 kinds of a/c’s. I need to know the difference. I am pretty sure I am using coolant based units. I hate to think that i am spending alot of money on “water chilling effect thingis”. When i start cooling my room with my portable a/c that has 2 ports to the outside, one for pulling air in and one for exhausting warm air back out, multiple humidity sensors in the room start going up. When i leave it to just the dehumidifier the room drops down to about 25% humidity but at 92°.

I had a single port unit that was just exhausting some of the room’s air outside as warm air. But this created a negative pressure in the room that ended up pulling air from the house despite my seals. So the humidity sendors started going up with that also.

For now i can only run my dehumidifier for the best dry air.

One of the most economical types of A/C units is a Mini Split.
I live in central Texas and have a small ranch with a cabin, as well as a remote office at my home. These both have Mini Split air conditioners. These get the room cold and get the humidity out. They are small and very efficient.

These have two parts. One is a unit that sits on a wall inside. There is also a small unit outside. The nice part is that the interface between the two is a small opening in the wall for small hoses and wires.These are very easy to install. Many run on 110v.

These are good mostly for smaller areas. My office is 500 square feet, which houses my computers and 3d printers. My ranch cabin is 380 square feet. My main home uses standard big ole air conditioners.

Believe me, we know air conditioners in central Texas, where it gets over 100F (40+C) for months every year.

Oh, and most Mini Splits also heat!

(Example: Right now outside it’s 101F and 79% humidity. Inside my office, it’s a cool 77F and 42% humidity.)

I think he is talking about evaporative coolers also known as swap coolers. Unless you are someplace dry like Arizona they are probably not the best choice.
It what you have is a compressor type AC and it is putting moisture into the room then there is something wrong with it.

Remember, if you have a room full of air at say 50% RH, and you cool the air, the RH goes up, but the actual humidity is the same.


Also, if the AC unit is too large for the space, it will short cycle and not do a very good job of removing moisture.

Your findings are totally OK.
With the A/C running you are removing some water from the air, never the less you are replacing some air with “fresh air” that is introducing water again.
The dehumidifier alone is removing water without replacing some air with “fresh air”. Thus you will end up more dry :wink:

All the Best

This sounds interesting. If I am trying to protect my filaments how do i assess my humidity at any given temperature? And from another perspective, for a given temperature and humidity how does this affect my filament? Can you ( or anyone) tell me how i can get a comparison chart for this? Although i expressed a concern for my son’s exposure to air born particles, my concerns for air in this room as being too dry for health is less of a concern.

ok. Thanks to FCLOWELL for pointing out the fact that I was using relative humidity. This is basic High school stuff that I had forgotten.

Here is a link to a calculator for the relationship between relative humidity and absolute humidity.

I had asked two questions:

  1. "If I am trying to protect my filaments how do i assess my humidity at any given temperature? Can you ( or anyone) tell me how i can get a comparison chart for this? "
  2. "And from another perspective, for a given temperature and humidity how does this affect my filament? "

Previously I mentioned that I was able to get 25% humidity at 92 degrees F. But that was relative humidity which is represented as a fraction to how much moisture air could hold at a given temperature (saturation point). What I need to watch is the Absolute Humidity which is how much moisture there is in cubic meter. Using the calculator above and assuming barometric pressure of 760 ( this only has minor impact anyway) the absolute humidity for 25% relative humidity at 33.33 degrees C (92 degrees F) is 9.08 g/m^3. After running the A/C with the dehumidifier i get 47% at 19.44 degrees C (67 degrees F) which the calculator yields 7.88 g/m^3 absolute humidity.
So 7.88 g/m^3 at 67 degrees versus 9.08 g/m^3 at 92 degrees. So that answers the first question. It is better at 67 degrees and I calculate that when relative humidity reaches 54% at 67 degrees then i get the same absolute humidity as 25% at 92 degrees.

Now to address 2nd question:
Everyone knows that entropy works faster at higher temperatures. So it stands to reason that given the same or lower absolute humidity you should choose cooler temperature. Of course you want to balance that with the cost to run the A/C.

What I really need is a sensor that reports absolute humidity. Does anyone know of one that is easy on the wallet ( <$200 )?