I need help figuring out a system that is not performing very well, nor has it ever from what I am told. I have two systems installed in a small house that has been converted into a restaurant. A 5 ton that is used to cool the dining area that works fine. The problem system is a 2.5 ton straight cool with a fixed orifice and no electric heat that is used to spot cool the kitchen. Both the supplies and returns are located in the kitchen and are the correct sizes. Neither of the coils are heavily soiled and the Freon charge is very close: delta-T 85/75 degrees; ID wet 76 degrees; OD dry - 91 degrees; suction line had 83 psig at 78 degrees; liquid line had 303 psig at 127 degrees.
To me, it seems because of the high heat load, the system might need a larger piston (if so, about how much larger) and/or add some cooler return air from the dining room into the kitchen. What would you suggest?