Carbon Dioxide Refrigeration

[Plank!]

Let me revamp and resurrect this thread.
I don't understand the principle of operation of this defrost.
In a R717/R744 cascade system, in order to defros CO2 evaporator, NH3 is taken off the condenser and then what?

You've missed a small detail in Andy's post - no mention was made about using NH3 (R717)

liquid R744 (CO2) is taken from the condenser - actually its from the HP reciever - then boosted in pressure and fed into the defrost hot gas generator, where heat from the high stage oil coolers is used to superheat the liquid into hot gas suitable for defrost.

Star have this system patented so perhaps if you need more info contact them or Andy P.