Evaporator reduced capacity.

[Pykester1]

Hello.
Has anyone experienced a total or partial blockage in a venturi distributor or any of the feed pipes coming out of a venturi distributor to a ceiling hung, forced draught evaporator? I have recently replaced a compressor on a freezer cold store, and the system seems to have lost about 5 degrees Celsius. Before the compressor was replaced (according to the data logger), the unit always ran at -20. Now it won't get colder than -15. The system is fully charged, the superheat is about right, in fact every thing seems normal. The only annomily is that a quater of the return bends on the evaporator don't seem to frost over like the rest of them. Could the coil be oil logged or could the venturi or venturi pipes be blocked?
I think the system was sized on its limits and this small difference in performance is enough to cause a problem.
Any views would be appreciated.
Regards

[desA]

Why did you need to replace the compressor?

[Sandro Baptista]

Refrigerant?
Suction pressure?
Air temperature at the moment of the suction pressure measure?

[Sledge]

If you have a blockage of the venturi or tubes, it would not impact superheat. The TX would react on evap outlet conditions and regulate flow to maintain superheat.

I would agree with you...if the tubes are not frosting the same, then there is a difference of flow. If there is a reduced flow through the evap, then there would be reduced capacity for the system.

[monkey spanners]

Just a thought, if it is a blockage, it could be anywhere between the distributor and the header at the other end of the evaporator.

[Pykester1]

Because it burnt itself out.