r-502 head master valve

[fridge_kid]

i have a walk in freezer using r-502 it hasnt been coming down to temperature after another service tech over charged system. i know the tech and beleve he used 502 and didnt introduce a non condensibles i think he beleved the system was low due to the temperature rise in the cabinet. i recovered the refrigerant and now find myself fighting with the unit today the pressures were 160 on the high and 5 on the low, it was cool out today 60 degrees farenheit ist he head master valve limiting the flow through the condensor? and not allowing it to reject heat or do you belevie it maybe an underlying issue in the txv? any help is appreciated thanks
-kid

[install monkey]

is there a sight glass on the liquid line,if is full then u need to look at the txv, of empty check the td accross the liq drier, iover 1 deg then change it otherwise -is this master limiting valve an evaporator pressure regulator?
are u getting 14deg accross ur condenser air on/off.how much subcooling are u getting

[fridge_kid]

in everyones opinion whats the best way to check a txv under this circumstance?? thanks!

[monkey spanners]

If the txv is being supplied with liquid refrigerant (with no or few bubbles) and at a good pressure, i would be looking to see what the evaporator superheat is at (assuming its not a mop valve) and based on what this works out as and what i feel would be reasonable given if the room is down to temp or not (and how well the rest of the system is working) is how i'd decide to inspect the txv inlet strainer or fit a new valve.
Also sometimes when they god bad, they don't respond much to adjustments to the valve stem, always note how many turns you give it so it can be put back as was if the fault later apears elsewhere.

Did the first tech put the right refrigerant in? And are you using the existing system charge to make your tests? If its had the wrong stuff put in the txv will have no hope of working as intended.

[texas64]

Hello,
Suction pressure looks low.

Try this:
Replace the filter drier, evacuate.
Add charge until sightglass is full.
You should be seeing about 20 psig suction side.
Still the same? Then replace TXV or TXV power cap.