You could measure all the tubing in the system piping and both coils and calculate the internal volume. Then work out where there would be various vapor volumes at the various pressures. And so forth.
Or you could look up the total receiver volume for the system refrigerant and then use 75% of that as the charge. If you have to bid the job - use 100%. <g>
I have worked on systems which could not be pumped down - but not very many.
Originally Posted by cthegreat1
The conventional view serves to protect us from the painful job of thinking.