I'm maintainencing a 540 ton Mcquay centrifugal chiller. Model is WSC 087. The suction superheat can not be controlled properly. When the chiller run at higher capacity (for example,70%), suction superheat is about 1 ℃, subcooling is about 4.5 ℃ When chiller run at lower capacity (<50%), suction superheat increases to 6 ℃, subcooling is 2.5 ℃. According to manufacture data, the rated suction superheat at different capacities (from 10% to 100% load condition) is 0.6 ℃. Is there some problem with TXV? BTW, why is the rated suction superheat (0.6 ℃) so low for flooded evaporator? what's impact of high suction superheat on system? How to quantify this impact? COP decrease? Loss of refrigerant effect?