Can someone explain Manual D results?
As recommended by the HVAC world and Mr. Udarrell I performed this test and the Manual J for example,the program recommends 700 CFM and 700 FPM for supply and return, but Mr. Udarrell and others recommed @350 FPM for return which is a very big difference. So, for example if you have to pysically use three return ducts back to a 5 ton unit a 16", 14" and 12" is equivalent to @ 2,000 CFM and the FPM would be at least 700. But, if you select 350 FPM for the same three return ducts needed it recommends a 20", 18", and 16" depending on if you add additional rooms on each trunk. CFM wise it now totals 4,000 CFM which in theory makes since, but isn't the system now not balanced because you have 2,000 CFM supply out and 4,000 CFM returning? Can someone explain is that too much CFM because everything I've read, everyone says you can't have too much return, but this seems to be too much.