Not cooling

[1954bill]

I work for a air compressor company, many air compressors have refrigerant dryer's in them. These dryer's main difference from a many residental systems in they contain a insulated heat exchanger for an evaporator. I was sent last week to replace a locked up compressor. I changed out the liquid line filter, and the Hot Gas Bypass Valve HGBV along with the compressor. I did an exact charge of 3.9 Kg of R404 after vacuuming the system for 3 hours, down to 750 Microns. When I went to start the dryer, it fail to come on. I tried lowering the pressure switch from 70 psi and it turned on and off; I lowered it some more and again it did the same. I turned the HGBV in, my gauge pressures lowered around70 to 60 psi, it started running but not cooling. I took amp load readings and found the 3 phase comressor to be pulling 8amps on a 16 FLA compressor. The compressor eventually kicked off on thermal overload. Any help?

[chad_nc]

When You weighed the R-404 back into the system did you charge it with a liquid or gas? If I am not mistaken R-404a is a blend of 3 different refrigerants (R-125 44%, R-143a 52%, R-134a 4%) and will seperate if charged with a gas causing weird pressure readings. Just a thought

[makinmoney]

Was there any oil in the old compressor when it locked up?

[absrbrtek]

Bad metering device. Unit probably has a TXV or a cap tube on it. Your not feeding any refrigerant into the evap besides the HGBP. Probably why the old compressor took a powder. JMHO