Hi AlexG, Ranger1 and Magoo
Well after evacuation for 12 hours and holding vacuum for a further 12 hours we charged with New R22 from a very reputable supplier.
I will change the oil filter and oil tomorrow and see if that makes a difference.
The oil cooler takes up the top 3 rows of the condenser coil. The oil pressure transducer is on the return oil line before it enters the oil filter housing. The control monitors difference between discharge pressure and oil pressure for High differential cut out and also monitors oil flow through compressor and cuts out on Low differential if the oil pressure is too low.
The chilled water temperature split is small because the client has more than design flow through the evaporator. The flow is however within the limits for this particular chiller. The design was originally 5 Deg split at the design water flow but they have increased the water flow as they have added an AHU to the system.