Freezer cabinet problem

[klimek]

Freezer cabinet set point -18. Was running fine for 1 week and temperature drop to -13.So my boss said to change for expansion valve with MOP. And again cabinet was fine for 1 week and again temp drop to -11. Cabinet is connected to compressor pack with suction pressure set 1 bar on 404A. What that can be that after one week is something blocking exp. valve?? Is that moisture, but other cabinets and coldroom are OK.
Thank you in advance if anyone knows whats going on?

[The Viking]

My guess, based on the fact that the rest of the kit is working OK, would be that you are looking at something specific for this cabinet...

Is it defrosting OK?

[Chunk]

Hi Klimek
I had a similar problem recently and accidentally fitted an MOP txv to cabinet and it still had the same fault as before,so i replaced with original valve and it worked perfectly.So your best bet is to get the case back to what was originally installed and start again.

[Chunk]

If this fails to help,make sure the defrost heaters are not permanantly on or if you are using hot/sat gas defrost that the valve is not letting by.

[powell]

Sounds like an defrost/icing problem. Is it iced up after the 1 week running time? Does it have at least 4 defrost settings? Is the cabinet sealed properly from the surrounding ambient?

MOP TEV's are normally installed to protect the compressor from high SP during a high load situation and after a defrost. Used in conjunction with a CPR valve could cause trouble but, refrigeration systems are designed for a 18-20 hour run time in a 24 hour period. This should rule out the TEV since the system runs great for a week then problems occur.

Of course, I'm assuming you did use proper clean up procedures and pulled a good vacuum on the system.

[Kh1971]

did you check the evap, any ice ? did you check the defrost cycle? please see if there is any disturbance from out side air flow to the unit. what kind of unit it is?

[Andy T]

Is the TEV bulb clear of any ice from the evap coil.You should Not use MOP in a multiple system that has normal valves fitted as this will be the valve that will close down first if th suction pressure increases.Especialy with after stubs come off a hot/cold gas defrost.Other things to look at are.
Is the coil frosting the whole coil.The valve may be shutting down to early.(reasons superheat set wronge.Poor location of file.Valve in block of ice.Short of refrigerant.Valve restricted.)
Is the coil iced up.(reason defrost terminating to soon,blocked airflow vents.(boxes of food in vents.Insulation fallen off in vents.),Defrost heaters failed.defrost clock failed,drafts causing damp air to break through air curtain.Evap fans failed.Check each one to make sure are spinning and the right way.It sound to me that you may be looking to deep into the problem.start from the basics and let us know what you find.