I purchased what is claimed to be a 1/8 hp chiller that was originally designed for a mattress topper. It runs a closed loop water circuit through a small pad that I put in the plunge bath. I will post a link and photos if that is allowed.
So far, it cools the water down by about 10 degrees F below ambient. I found that I needed to add some glycol to the cooling water loop to prevent the coils from freezing up. I also found that I needed to circulate the water in the tub to increase the heat transfer and prevent the chiller from shutting off when it got to the minimum set point 4 deg C (39 F). So far, it seems to be worth the $150 I spent. Next, I'm considering changing out the cooling pad to some type of wort chiller or other copper tubing that might give better heat transfer without circulating the tub water around it.
