Main house system 4 ton nordyne is very low on refrigerant running at 200 psi with 40 PSI suction. Equipment is 14/15 years old manufactured November 2010 with our fortuna refrigerant After careful consideration and knowledge of up to $1,800 The decision to recharge for the remainder of this season was made. A full system charge requires 18 lb or 410A. Today I used 176 oz equivalent to 11 lb One single dose of xanthos brand max seal refrigerant stop leak with ultraviolet dye Water flush both condenser coils New running refrigerant pressures are 133 with 11 superheat and 312 with 8 subcooling Recommend replacing main house system furnace and air due to age, refrigerant leaks, obsolete repair parts and outdated refrigerant