Headache for 2 solid door freezer

[jayryu]

I have in lost finding solution for 2 solid door freezer. Usually the freezer kept around -10 F, after defrost problem fixed it doesn't go down under 6.5 F. I have changed the tev recently but no changes. The data are as follows.

compressor : AJA2425ZXA
gas : R404a
box temp: 6.5 F
suction p: 21 psi
compressor inlet temp: 25.5
discharge p: 233
receiver out temp: 97.3
condenser inlet air: 83.8
condenser out air: 96
super heat value: 38.6
subcool : 2.2
sight glass : clear
compressor ampere: 7.5
condenser TD : 15.7

I am thinking about inefficient compressor. Is there any idea? What is the solution?
Please help me, I am in really severe headache.

[Glenn Moore]

Your suction superheat is much to high at 38.6 , suggest adjusting the tev to reduce the superheat down to about 10 f as your starving the evaporator of refrigerant , thereby reducing the capacity of the system. You may need some more refrigerant as when you own the tev a few turns to reduce the superheat , you may well lose your little bit of sub cooling, ideally you should have 8 deg subcooling for the tev to function correctly

[jayryu]

The TEV is brand new and I never adjust the tev from factory set unless absolutely necessary. Is this the case?
TEV is sporlan RSE-1/4-ZP. Before changing the tev it was working really fine. I thought TEV was short feeding, then changed the valve. But the condition is same before and after the tev change. This condition only happened after melting heavy evaporator icing manually. Before that happening the system was working really fine. Is it possible inefficient compressor issue?

[RANGER1]

Take Tx bulb off & warm in your hand.
Does anything change?
Is filter drier new?

[jayryu]

Here it is weekend. I'll try next weekdays. Drier is 4 years old.

[chemi-cool]

You have changed the TEV recently and did not change the drier?
Before you do what Ranger1 tells you, I suggest you replace the refrigerant charge which must be small, put the system under deep vacuum and continue from there.

404a and POE oil are very sensitive to moisture and by replacing TEV, you must have let some air into the small system.

[Glenn Moore]

You always adjust the tev to match the evaporator. Tevs are factory simply to a static superheat setting which often sees the evaporator being starved are poor evaporator and system duty is the result . It may be the valve is too small for the system . Also as Ranger has said you should change the drier every time you open the system to keep moisture levels as low as possible . So open the valve and get the superheat down to about 10 , if you cannot achieve this check the tev orifice size and fit a larger one or a larger tev. . Always adjust a new tev to a low as possible stable superheat, factory setting is simply a start point.

[jayryu]

Everything you say are very understandable. My doubt is if the tev was adjusted as underfeed condition, how the subcool is only 2.2. I have charged the system 2lbs and 4 oz of R404, the sight glass is clear, so I think gas is not short. If tev underfeeds, the subcool value must be more than 15, because gas is enough, not short. It is a small system and I think 2lbs 4 oz is over enough quantity. And if there is restriction on drier, it results as same condition of underfeed and high subcool.
Replaced tev is exactly same size with old one. I have changed compressor and drier 4 years ago, at that time I have charged gas 2lbs 2oz. It has worked fine for years until 2 weeks ago when evaporator heavy icing happened. After melting the ice and fixing the defrost system, the current condition started.

[frank]

Are the defrost heaters 'on' during cooling, thereby adding heat to the evaporator and causing the high superheat?

[jayryu]

to Frank: of course not.
I'll adjust superheat with tev soon.