you are a field technician...copeland and every other compressor manufacturer will tell you that you need 20F because you have crap equipment, spend 5 minutes on troubleshooting and you dick with the txv everytime you have a chance...well, maybe not you, but you get the picture.
if you are a manufacturer...then compressor manufacturers will allow you less because you test everything many times over with NIST equipment and then you write it down in the IOM that you need to have 12F suction superheat (or whatever).
that's the difference.
When she gets lonely and the longing gets too much
She sends a cable coming in from above
Don't need a phone at all
We got a thing that called radar love
We got a wave in the air...radar love....Golden Earring