Why is my 8,000 BTU dual-hose mod making the compressor hum so loud?

The fan sounding strained is a dead giveaway that you're dealing with static pressure loss. Those internal blower fans in single-hose units aren't designed to pull air through several feet of restrictive ducting; they're built to pull freely from the room. If your intake box is too shallow or your hose diameter is too small, you're effectively choking the condenser coil. You need to make sure the **surface area** of the intake port on your custom carriage is at least 1.5 times the size of the actual hose diameter to allow for better airflow transition. If you're using a standard 5-inch duct, try stepping up to a 6-inch insulated hose to reduce friction.

You also need to account for the fact that you've bypassed the unit's internal moisture management. Most of these R32 units use a slinger fan to splash condensate onto the hot condenser coils to evaporate the water and help with cooling. Since you're now pulling air from outside, which might be more humid, that water is going to build up fast in the internal pan. If the unit isn't evaporating it off efficiently because of the modified airflow, it'll trigger a shut-off or just run less efficiently. Keep a close eye on the drain plug or just run a dedicated line to a floor drain.

Another thing that's probably killing your cooling gains is the heat radiating off that exhaust hose. Even if you've separated the intake and exhaust at the window, that thin plastic exhaust pipe acts like a space heater inside the room. Wrap the entire length of the exhaust in **reflective bubble insulation**. It makes a massive difference in how fast the room temp drops because you aren't fighting the heat leaking back into the space while the machine tries to cool it. For the next version, skip the cardboard and go with something rigid like Coroplast or even a 3D-printed shroud if you have access to one. Use a parametric design that tapers gradually from the hose connection to the intake vent. Sharp 90-degree angles inside your intake box create turbulence that'll make the fan work even harder. If you get the airflow right and insulate the hot side, that 8,000 BTU unit should start hitting those lower temps way faster than the stock single-hose configuration ever could.

This project is freaking awesome! I've been wanting to try a dual-hose mod forever beacuse my apartment feels like a vacuum. Seeing you guys talk about static pressure and 3D printing is making me so hyped to start mine this weekend. Speaking of mods, has anyone ever tried painting their AC unit matte black? I’m worried it might absorb way too much heat if it’s near the window, but it woud look so much cooler than that generic white plastic!

Spot on with the static pressure advice. I did this same mod on my old Midea and learned the hard way that the blower just can't handle the resistance. One thing I noticed that people often overlook is the actual screen mesh on the window. If you're venting trough a standard bug screen, that mesh can cut your airflow by another 20-30% beacuse of the tiny obstructions. Pop the screen out or use a high-flow mesh where the hoses connect to the window kit. It’ll stop that whistling sound and let the fan breathe just a bit easier.

You’re hitting the limit of that Antarctic Star's blower. If you're serious about v2, look into the Suncourt Inductor 6-inch inline booster fan. Wiring one of those into your intake line will negate the static pressure issues your internal fan is struggling with. Also, check your R32 charge temps; if that compressor is cycling too fast, you might be frosting the evaporator because the airflow balance is skewed. I had a Whynter ARC-14S that acted similarly until I ditched the cheap 5-inch ducting for smooth-bore semi-rigid aluminum. Those internal ridges in standard plastic hoses are airflow killers.

I'm still realy new to this, so some of the technical talk about static pressure is going over my head. If I use a bigger 6-inch hose like you suggested, does the length of the hose matter too? My window is kind of far from where I want the AC, and I'm worried a longer hose will just make the fan struggle even more. Also, for the 'slinger fan' part, if it's super humid outside, will my AC just start leaking all over my floor if I don't have a drain hose ready? I really don't want to ruin my carpet while trying to make this more efficient.