hi, new to the forum but and have found some very helpfull advice all ready.
im mainly an ac engineer but have started doing a bit of refigeration serbvice work also.
just a couple of questions if anybody can help.

1. how long does a system have to be running for before you calculate superheat and subcooling.
i.e does the room or container have to down to desired temperature. to get accurate results??

&

2. for example, evaporator with air flow i.e fan motor.. you minus 12 degrees from evaporating pressure/temp on comparitor to find expected evaporating temp. how much do you minus to find evaporating temp for plate heat exchanger, say for a reach in freezer.

hope you can help with this