i came across this a few times already in my 2 year career, today on a walk-in fridge top half of evap is iced up, txv iced up at distributor, good airflow, clean evap, fans run, checked pressures after de-icing, 35/205 r-22, full sight glass. didn't suspect charge issues with a full sight glass. high superheat at evap 30 degress. opened up the txv a few turns got the superheat to 12 degrees. everything seemed to run well after that
my question is, why would the txv need to be adjusted all of a sudden?, this walk-in has always ran well for the two years i've been servicing this restaurant, have never had isssues, is the txv getting restricted and i'm compinsating by opening it up some more? or is it slowly crapping out, or is that normal to need to adjust txv's at times ?