Originally Posted by
hyperion
The duty of the system is not determined purely by the evaporator. All of the components are selected to provide the required thermodynamic cooling duty. By mismatching the evaporator all sorts of operational problems could eventually become apparent.
When the manufacturers upgraded from R22 to R407C, the systems were optimised to provide the original capacity.
The oil in your R22 compressor and system may not be fully compatible with R407C, which could potentially cause long term oil return problems.
Some of the drop-in blends may work fairly well in your R22 system, albeit with some fall off in duty.