high head pressure

I am a nh3 mechanic and have not had much to do with airconditionig. i am having trouble with a Apac airconditioner 36kw. what is the hp cut setting for R22? i found the after market high pressure switch was set to 3000kpa. i belive this is way to high. the head pressure slowy rise to 2500ka. the ambient temp 8 degress. suction 360kpa. air filter brand new wash out both coils. discharge air 31 return 19. the outdoor coil is wet and the suction line after the accumulator is forming white frost back to the compressor and down the body of the compressor is this normal? what are normal pressure for a unit running in heat? weighed in a new charge of gas and change drier. the unit is cutting out for some reason i think it may be head pressure (auto reset). always stops when i walk way from unit.