Issue with a Searle evaporator

[coolxpert7]

Hi chaps, new to this but:

Have been commissioning a 4 deg C pharmaceutical coldroom a Searle KEC40 cooler & matched Danfoss condensing unit. There is an identical room on the floor above which works fine but can't get the current one to meet the duty.

Evap temp is way too low - about minus 12°C when should be maybe minus 2°C. The lower two thirds of the cooler tubes ice up whereas the top ones don't seem to be receiving any refrigerant (R404A).

Expansion valves appear to be sized ok. The distributor splits 3 ways. Are there any known issues with distributors or anything similar?

I'm assured the system was nitrogen purged while brazing etc but didn't witness it personally.

Any input would be useful!

[nike123]

Is distributor positioned vertically?

[frederik79]

i would measure the superheat.Check the tev bulp , is it properly fixed on the suction line.Check if the tev is 404a.

[coolxpert7]

Yes, distributor is vertical with inlet at the top. Has to be a blockage in one of the three tubes? I think the next step is we change the coil - there are some other identical evaporators on site awaiting installation. Thanks for your input.

[stuartwking]

what size of orifice has been used?.
Is there a oil seperator/oil trap fitted?.
What is the subcooling/superheat on codenser/evap/liquid line/ suction pipe?.
happy hunting.