I changed out one 6 ton circuit on a 2 circuit 12 ton RTU and converted a 5 ton split system both to NU22B. The building owner wants something less expensive than R22 to use when we find units with issues. There are about 65-70 units. Both of the units I changed over have high superheat. I followed instructions and started at 80% of original charge and on the RTU I ended up with about 2 lbs over. I never got below about 35-40 superheat. It seems to cool fairly well as these units are about 15-30 years old depending on which end of the facility I am working on.
If I remember correctly, the RTU had an orifice and the split system had a txv. Both had the same thing with high superheat. Any ideas? Is this normal? At the time of conversion the indoor temp was about 90-95 and the outdoor was about 100-105.