QUOTE (Sk_rmouche) :
These types of compressor are not intended to be used with this kind of system. Rotary compressors are mainly used with air conditioning and industrial application in low to mid power. Power charts aren't available for such low T° as -60°C because there's no application for that.
You'll find that in low temperature industrial system, cascade and autocascade system trust the market because it's more convenient and a little bit more efficient than using a single-stage to achieve -60°C at the cold plate.
Your compressor is quiet big and you have to ensure that there will be enough cold gas a the suction pipe to cool down the compressor. The electrical power should be quiet low running at -60°C and rotary compressor motor usually runs at higher temp° than other types of compressor because of its design ( motor is @ HP pressure and temp ) but there is not an easy way to determine that from known values like at -15°C because volumetric efficiency is very poor at theses values.
Thanks.
There is no other method that the definition an empirical way? Only practice?