walk in freezer icing after expansion valve

[indoorairpro]

When I arrived discharge temp from evap was about 10 degrees.
everthing after expansion valve frosted over.
Sight glass was not clear
outside ambient temp about 20 degrees
only one condensor fan running due to ambient temp
cond labeled R404A but there is possibility of mixed refrigerants according to owner
low psi 3 lb high around 150 and sub cooling to low to read accurately.
Since I knew siht glass should be flooded wspecially with such low ambient temps I added some 404a.
low only rose to about 5 lbs high rose to about 250 and sub cooling also went up to about 15 degrees
Discharge temp in box droped to about 10 degrees and sight glass was still bubbling although not as much.

At this point something happened between my boss and owner I guess about price so I was asked to pack up and leave but was wondering what you veterens would have done next and if you had to guess what would you think the problem was.

Also did put into defrost and defrost cyle was working although there did not seem to be any type of pumpdown. Condensor just turned off when t went into defrost.

Thaks in advance for your response

[2sac]

Wht shouldn't a freezer ice up after the valve? Sounds like you have other issues. We need more info before proceeding.

[indoorairpro]

Understood but I was not there long enough to collect any other data and generally dont spend much time working on freezers. I would expect some frost after expansion valve but is solid ice normal? wouldnt defrost cycle knock that down?

again was not looking for an answer just some general opinions. More interested in why high side was high but still had bubbles in sight glass. If expansion valves was closeing for any reason plugged, broken overcharged whatever , would that not cause sight glass to clear even faster as liquid backed up to condensor?

[KB Cool]

Your low side pressure too low for a freezer running 404a. Is your dryer before or after sg?

[jpsmith1cm]

Sight glass was not clear

You need to remedy this first.

[bunny]

low psi 3 lb high around 150 and sub cooling to low to read accurately.

Seriously????

I would love to hear an explanation on the sub cooling being too low to measure accurately.

[cavalieri85]

Step1 if mixture of refrigerants is suspected than before anything else recover, change drier, evacuate and recharge.

[Navy06]

If I was told there may be mixed gas in system I would have pulled the charge and also changed out FD on system. also after the txv there could be moisture in the system causing the ice up on the lines. next step would have been to do an efficiency test on the comp.

[malcor]

If I was told there may be mixed gas in system I would have pulled the charge and also changed out FD on system. also after the txv there could be moisture in the system causing the ice up on the lines. next step would have been to do an efficiency test on the comp.

I'm curious, do you actually repair commercial refrigeration equipment?

Don't mean to be rude but your recommendations, and a couple of others, really has me wondering...

[indy2000]

txv and feeds freezing..........is normal in LT.

Some of our bigger MT evaps even show frosting at times...dew and freezing point.

I think when you mentioned subcool is too low to measure, you meant there was NO subcooling, as you indicated the sight glass was flashing.

As mentioned you need to establish solid liquid to txv, and then measure SH from the evap.

From there you can make other judgement calls..........but seeing you got called off, its obvious the customer is looking for cheap and dirty fix.

Look at the TXV label to see what possible refrigerant is in the system.

[cavalieri85]

It doesn't matter what the system is doing as long as he has a zcontaminated system with mix of refigerants this unit won't work

[malcor]

It doesn't matter what the system is doing as long as he has a zcontaminated system with mix of refigerants this unit won't work

Customers can sometimes provide useful information or clues. In this example the customer said that there was a possibility of mixed refrigerant. That information may or may not be helpful, depending on what information they are basing that assessment on.

At what point would you step back from changing parts and actually diagnose the fault?

[cavalieri85]

Well with an erratic system and only having limited info given to me at this point. Eliminating any possibility of mixed gases seems a good option. Of course looking at my superheat subcool comp amps and performance of system are a prerequisite to my suggestion. I am confused about what you are suggesting. Of course I would diagnose the unit!! Usually when a customer says this may have happened means it definitely did