What to do next ?

[suhreman]

I have a Walk-in freezer which is 404A. It has 2 evaps and each has its own expansion valve . Temp is avg'n around 19 degrees (YIKES)... Mechanically everything seems fine . My pressures are 19/low 200/high with about 60 degree outside air temp. 19 psi w/ 404a converts to -15 and my temp after evap is 22 .. so thats 37 of superheat .. The evap is frosting up obviosly .. but i dont want to adjust any expansion valves cause it was running b4 and now its not .. The unit was pump'd down and the compressor seems to be working fine .. i also pulled a vaccum and recharged till sight glass was full.. at first i suspected expansion valves , but both coils are frosting up equally which also leads me to believe they are fine and its something else .. but im lost to what else it could be .. i pumped the compressor down to zero and it held pressure , so i didnt suspect valves .. basically im lost and ive tried everything i could think of . maybe im just missing the obvious ? Any direction or advice would be greatly appriecated .. Thanks in advance

 

[Fzob]

Sounds to me like your charge is low.

 

[imok2]

suhreman,
Here's what I would do! Take a superheat reading off each evap,if they have an external equilizers on them use line tap on each equilizer line and install guages on each coil with a thermocouple at sensing bulb of each one to get proper SH readings they should be about 4/5 *F ,(you can always take them off later if you feel they will leak), pressures on coils should be pretty steady. Now measure the subcooling out of the condenser it shoild be about 10*F on a steady load. The head pressure indicates a sat. cond temp of 89*F so you should be reading a temperature of arounf 79/81*F in the liquid line to X valves. At this point I suspect a partial restriction in X valves or drier
Roger