Walk in freezer queries.

[PaulYeates]

Walk in freezer with a block of ice forming around the Thermostatic Expansion Valve, with an uneven frosting on evaporator coils.
The room has no problem reaching set point and the refrigerant level in the system seems normal.
Unit is running on r404a.
Is it necessary to allow a little more refrigerant enter evaporator by adjusting the TXV?
Should I check superheat and what's the best way to get the reading?
There is no evaporator schraeder valve.

[craigdoyle1982]

Check the orifice is correct size for the room pump it down check it for Debris also

[The Viking]

OK,
Before you open the system to change orifices or start to adjust the TXV, just a thought or two...

1. Have you checked that the evaporator is clean, with a free and even airflow?
2. Check that the defrost cycle functions as it should.
3. Check the super heat.


The super heat is the difference between the ºC temperature readout on your suction gauge and the actual measured pipe temperature ºC by the TXV bulb. (and if there isn't an access point by the evaporator, assuming it is a fairly standard installation, the suction pressure by the the compressor won't be far out)

[PaulYeates]

OK,
Before you open the system to change orifices or start to adjust the TXV, just a thought or two...

1. Have you checked that the evaporator is clean, with a free and even airflow?
2. Check that the defrost cycle functions as it should.
3. Check the super heat.


The super heat is the difference between the ºC temperature readout on your suction gauge and the actual measured pipe temperature ºC by the TXV bulb. (and if there isn't an access point by the evaporator, assuming it is a fairly standard installation, the suction pressure by the the compressor won't be far out)

Thanks!
What would an acceptable superheat reading for a freezer room? Set point -20*, -30* evaporating temperature.