30 ton split system using existing 30 year old coils. All lines left in as well as accumulator. Txv's were replaced as well as liquid line solenoids. Suction line filter added and lines blown with nitrogen. How much left over oil in the system is acceptable? The coils had to stay I wish it could have been replaced. Holes were drilled in the traps and taps were added so oil could be drained and blown out with nitro. Thoughts and feelings? Unit is not fired off yet. I am thinking of removing accumulator, and flushing with a flush kit.