TrashBench Turns a Junked Air Conditioner Radiator Into a Massive RTX 3080 Cooler

Australian YouTuber TrashBench decided an old outdoor air conditioner unit sitting in the trash deserved a second life as the biggest radiator his test bench had ever seen. He took the outdoor half of a discarded Fujitsu split-system rated for four kilowatts of cooling, emptied the refrigerant, and kept only the parts that matter for water cooling: the large finned coil, its axial fan, and the pump.

Most of the compressor gear came out of the box, a regular computer reservoir was shoved into the enclosure, and casters were bolted on below so the whole thing could just roll around the bench. On the opposite side of the loop, he heat-bent a T-fitting into a Y-split and printed special brackets to keep the cold plates in place. The original pump is still as loud as ever, but the rest of the equipment just feeds coolant through conventional tubing to the CPU and GPU.

Testing began with an RTX 5060, which was running hot, sitting at 52 degrees Celsius under load with the OEM air cooler. However, after the air conditioner loop kicked in, the temperature dropped to 33 degrees. It even allowed the boost clock to increase from 2902 megahertz to 3300 megahertz, despite the fact that average frame rates in games increased by only about 3%. The RTX 3080 came next, a card that has always generated a lot of heat and consumes a lot of electricity.

With the stock air cooler, the GPU reached 65 degrees Celsius, while the hotspot reached 79 degrees. When he switched to the air conditioner radiator, the GPU temperature dropped to a comfortable 28 degrees Celsius, while the hotspot plummeted to 42 degrees. Yes, the power restrictions, which ordinarily range between 320 and 350 watts, were increased all the way to 459 watts, and the core clock reached 2130 megahertz. Even after an overclock, frame rate gains were small, averaging around three percent, with games such as Cyberpunk 2077 and 3DMark Time Spy showing very minor improvements.

One final test coupled the RTX 3080 with a Core i9-14900K processor, and the processor benefited from the configuration, with temperatures dropping by roughly 18 degrees in certain tests to 76 degrees. Though combined loads were a different story, the builder determined that this was due to a minor issue with contact between the water block and the chip. Throughout those runs, the graphics card remained at 28 degrees, indicating that the four-kilowatt radiator handled the combined heat load quickly.

Results like these highlight how much thermal capacity an ordinary residential condenser carries compared with typical computer radiators. Noise from the original pump remains high, and the unit itself takes up considerable floor space, yet the temperature numbers leave little doubt about the raw cooling ability on offer for anyone willing to work with discarded hardware.
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