T.E.V. adjustment.

[digerious]

a tev with the correct orifice, i was taught, should only need adjusting no more than one turn either way when setting up.inside a danfoss tev box there is a selection guide for each orifice.each orifice is suited for a certain range of duty at a given evap temp and refrigerant. the adjustment is there to allow for the difference in duty each orifice is allowed.slight adjustment is expected.its when adjustments of 2 or more turns are needed that alarm bells should ring.rightly or wrongly i was taught in college that when a system has run, not slightly short, or nearly empty of gas, but roughly at half charge, the mixture has the capacity to cut away at the orifice seat and allow more refrigerant through than is required, causing flooding to comp.this aswell as partial loss of bellows charge, along with all the more obvious underlying faults are the only reasons a tev may appear to require massive adjustment

[NH3LVR]

i was taught in college that when a system has run, not slightly short, or nearly empty of gas, but roughly at half charge, the mixture has the capacity to cut away at the orifice seat and allow more refrigerant through than is required, causing flooding to comp.

What they taught you at college is indeed correct. I had this happen in a system that had been undercharged and ran for a long time. The system was a blast freezer running R502. At the end of the cycle when there was little load we started to get flood back. That was an easy one to figure. The process is called wiredrawing. It seems to be more pronounced on ammonia systems. Steam does this as well. Anytime you have a mixture of liquid and gas this can occur.