I'm looking at building a direct phase change system that can hold temperatures with an accuracy of +- 1C from -10C to 110C. It needs to hold 100W at -10C. I'm planning on using a 1/4hp compressor running 404a with a heater cartridge in the evap and using an OMEGA PID controller. EVAP.jpgEVAP.jpg

The Evap is a copper block roughtly 2"x2"x1" with fins. The outer piece is molded plastic and there will be spray foam between the plastic and the evap.

I'm also planning on using a hot-gas bypass valve

How difficult would this be?