Quote Originally Posted by Big SturL View Post
It will be in an SS yes. The use of butane was to help condense the propane EVEN easier, so that one could use a very small compressor and condenser, and still achieve good temps.

HOW greatly the butane will affect this, I don't know, that's where the leet's come into play.
Keep in mind that the lower the pressures are doesn't mean the system will work properly . That's the main probleme people who make 3-stages cascade with ethylen-ethylen have : ethylen can condense in the second stage, and the HX2-temp is under -80°, a this temperature the ethylen doesn't need >5bar to condense and so you just get a little mass condensed, and you have to use big compressors with high displacement and flowrate to carry any load. You'll get the same problem here, you should ever be >8bar on discharge pressure, compressors are designed that for, propan condense very easily and such gases as R12-R600a are used with passiv condensers as the ambiant temperature is around 45° and then the system work properly