Refrigerant R-407C

For continuation about the question: here are the COMPRESSOR DATA

• Comp Type: Copland-USA
• Type: Hermetic Scroll
• Model: 2 x ZR94
• Power: 400V/3Ø/50Hz
• Evap. Temp: 7°C
• Cond. Temp: 65°C
• Total Cooling Capacity: 35.9 kW
• Total Comp. Input Power: 18.1 kW
• Unit Total Input: 19.7 kW
• Comp Max. Current: 31 A
• Unit Max. Current: 36.4 A
• Refrigirant:407C
• Comp No: 2
• Refrigirant Circuits Ind'l: 2

The compressor make us a lot of trouble. it is tripping in high pressure and sometimes in electrical contactor relay. The compressor is tripping but the AHU is still running. And we still studying what is the cause of this troubles. We suspecting the characteristics of refrigirant that is why I wrote here. Thank you to all that shares the information...

As mentioned in my earlier note generally R407C is used as a retrofit refrigerant to replace R22 in the existing systems. From your data it appears that your system is DX type and must be new one. It is mentioned in the data that the condensing temperature is 65 C. Therefore normally the system should work on middle east climates where the ambient temperature goes around 40 to 45 C. Check your condenser coil. Is it cleaned properly. Check the E.D. Possible causes may be refrigerant overcharge, dirty coil, slipping condenser fan belt ,or condenser fan motor not working( I assume it is air cooled) air or non condensable in the system. Check with the supplier's manual and diagnose the problem.

Can you provide some sample data on how the unit is actually operating? Suction pressure, condensing pressure, air/water inlet and outlet temperatures, motor amps?

Thanks! This could be good information. I will try to analyze it, but it might take a while.

Excellent data!

Questions:

-what is the age of this equipment

-did it come with R-407C or is this a retrofit

-if this is a retrofit due you have the baseline data from before the change out

-what is causing the spikes in your return air temperature, as they are associated with your compressor trips

-That is new equipment.

-it came with R-407C.

-the high temperature in return cause by high ambient temperature and the tripping of the crompressor, maybe sometimes it trips for how many hours before we go in one system.

From what I can gleam from your data, the increase in load leads to higher suction pressures therefore higher discharge pressures. Eventually your systems trip-out on high head pressure. The simplest thing that I can suggest is that you limit the suction pressure by installing a CPR (crankcase pressure regulator) valve in the suction lines, upstream of the compressors. This will allow you to physically limit the maximum suction pressure at a level that will prevent the head pressure from exceeding the high limits.

This may reduce your capacity at high ambient and load temperatures, but the units will still run.

Many if not most of the shutdowns seem to be associated with high suction pressure, as if the refrigeration system is trying to pick up a sustained extra-large load.

One possible solution for this would be to retrofit a crankcase pressure regulator in the suction line to each compressor.