The original designed of chiller does not put an oil drain at the PHE.Last time we had an ammonia leaked at the blind flange.We found out that there were some oil stuck in PHE,no where to go.What is necessary to put an oil drain at PHE ? Why oil leak to ammonia line ? and How do we know the efficiency of the system drop if cause by oil at PHE ? It will take longer run,right ? Help me please guys.Thanks alot.