Rotovap chiller on a budget

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I just thought I’d share my experience with a DIY chiller. This is a 5000 BTU LG chiller from Amazon ($147) and a $59 64 quart cooler. Make sure you get a AC window unit without a heater and dehumidifier.

I cut a hole for the water pump dropped it in there. Carefully removed the evaporator coil from the AC unit and dropped it inside the cooler. Rewired the button on the front so that the fan switch now turns on / off the compressor, and the fan is hardwired to always be on low. The whole setup took probably 1 hour to complete.

I filled up the cooler with about 11 gallons of water. It took 40 minutes to bring the water down to 1C.
For a 5L rotovap running at 55C it’s able to keep the water at 3.3-3.7C with the compressor running constantly. The heat being dissipated from the AC unit is warm, but not hot. So no worries there.

I know that this shortens the lifespan of the compressor, so if you get a slightly larger AC unit you can probably use a temperature probe and switch the compressor on / off automatically.

Anyways, it works like a champ; no more hauling ice.

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This is a teardown of the AC unit. Keep in mind that there is a sizable capacitor (to kick on the compressor) in these units. A capacitor like that can mess you up, to be safe either short out the capacitor before rewiring or leave the unit off for a few hours and measure the voltage to make sure it’s been discharged.

Be careful!

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I had my water pump hooked to a water chiller and it worked like a champ. No more swapping ice bottles or cold water.