Stulz Expansion Valve Problem

[Neddy]

Hi everyone,
Long time reader, first time poster so go easy on me .I have two Stulz underflow units side by side in a computor room. The model no. is CCD 121A. Unit on the right works fine. Replaced the compressor on the left unit and ran it up but found it not cooling well so faulted the expanson valve. Suction pressure was high and had a high superheat. The valve I faulted is A Danfoss TEZ2 which was not the manfactures orginial valve. The manfactures valve is an Alco TX3 N25mm PCN 801929. I was unable to get this valve so an Alco TIE NW PCN 802436 was sourced for me. Now my suction pressure is 5.5bar much the same as the last time.High superheat. Liquid line pressure 18bar. Suction temp 18. Discharge 90. Evap Air on 23 ,air off 18.

Do you always have to change expansion valves on close control units like for like or am i missing something?

Any help would be much appreciated.

[Neddy]

Any Stulz or Close control experts?

[Brian_UK]

Be a little patient Neddy, some others may still be working or sleeping in other parts of the world.

You've given pressures but not the gas used.

Why was the compressor changed ?

[Neddy]

Thanks for replying Brian_UK. This is a new site and this unit has had a replacement compressor all ready possibly due to the high superheat. Found the old compressor down to earth. Fitted the new one with liquid and suction burn out driers. Sorry on R407C gas .

[aliman]

Have u got the correct size orifice installed?

[tradybrad]

hey
is the systems condenser water cooled or air cooled? Have you checked expansion valve sizeing to compressor capacity? What is the high pressure on system?

[Neddy]

Hi aliman it's a size 3. If it was too small I'd expect a low suction pressure and high superheat. If it was too big I'd have a high suction pressure and low superheat. I have a high suction pressure and a high superheat which is strange. The valve file seems to be sensing the high superheat hence the high suction pressure but I'm getting poor Refrigeration affect.

tradybrad is an air cooled consensus. The valve was sized based on the orginial valve. The original valve was specially made for Stulz by Alco. It can only be purchased from Stulz. Stulz where unable so supply the valve at the time so a similar valve was sourced. Someone had fitted a Danfoss valve before I faulted it and I fitted a new Alco one. The Danfoss valve had the same symptoms as the new Alco one . Is there something I'n the design of the original valve that's different to these valves?