To recharge if the system is empty is between 21 to 26 oz. The system doesn't start to get cold until around 22 oz or so.
I takes a while to get it in. Normally you keep the can upright. I tend to move the cans from upright to on its side and increasing the idle some. Don't fill with the can upside down. it will freeze the reed valves in compressor and ruin it....
Bob
