so here is what we know: . single circuit and no branch off to solenoid valves for staging and only one txv on the evaporator coil. Also No oil trap at the ahu on suction line . Unit has 2) 25 ton 06e compressors . the ahu is 100% oa . we installed 1 compressor in 2 of these units installed the same way. we already blew the head gasket on one and lost the charge and now we lost another compressor, and actually there's been several compressor change outs as the one's we replaced were rebuilds. unit is only 13 years. (there is an accumalator at the condenser). we know that it's completely installed on the wrong evap. coil and the piping configuration is also wrong at the ahu. i think the biggest problem is the one txv on the condenser, i briefly talked to carrier and they told me to walk and good luck. any suggestions would be great. we cancelled our warranty on the compressors for system deficiencies and cust. is looking for answers to try and save these compressors. surprisingly, they understood as if they've gone thru this with other contractors. oh the seq. for these condensers are as follows, staging is supposed to be thru the LL soelnoid valves at ahu and compressor # 2 cycles on press. if coil loads up and suction gets above i believe 83 it comes on, if it drops below 53 it kicks off. there is one mechanical unloader one the 1st stage compressor.
some operating #'s with one compressor running :
30 psi oil diff.
sight glass is 1/8 full
inlet air to evap. 86*f
outside air 86*f