For residential you can use a max of 1000-fpm velocity, but many recommend a max of 900-fpm on main, branch runs 600-fpm.
Originally Posted by punklethal
For that 3-ton system, I would have sized the duct system for 1300-CFM; 16" metal; @ 932-fpm velocity.
For a 2.5-ton; 15" rd. main if available; 1100-cfm; @ 897-fpm. Friction Loss Per 100' of duct, 0.09 IWC.
For a 2-ton; 14" main; 900-cfm; 842-fpm.
tinner73, my software for 2-ton, 800-cfm, I get a 13" duct; @ 868-fpm; FR is 0.10" | However, I would size for 900-cfm. Though, your figures are okay.
With your figures I get; 12"; 800-cfm; 1019-fpm; FR 0.15" WC per 100'.
Size the return equal or a little larger.
Airflow is everything.
The existing 3-ton with a poor duct system, may be delivering around 1½-ton. (?)
Reduce the heat-gain first; then do the manuals J, D,& S, & stop guessing. - Darrell
my Trane ductulator has me @ .2" of friction.
FILL OUT YOUR PROFILE!!
Hi tinner, Your ductulator may be right, but that is very high for 100' duct run of friction loss. Most want 0.1" down to 0.06" or so, on the supply side, even lower on Return.
Originally Posted by tinner73
All I have is software now, no ductulator. - Darrell
the ducts are flex ducting R 6.0 so maybe I am undersized a bit. I checked for leaks everything looks good and ok. The air is coming out of the vents and the furnance is set for 3.0 blower speed medium low setting on this unit. I guess maybe I am undersized thanks you guys.
may your ac may not be charged right have it checked for proper operation could be way overcharged or under charged call a real tech to check it
Thats the first thing I did. He asked me if the original installer added any freon. I said no. He checked it with his gauges to see if charge was off and added some freon said the air was not cold enough to combat the heat. Since then the unit has been running better but still cant fight the heat. Maybe I will call him back and look at my duct work for me.
Could be duct leaks,undersized ducts,etc..
what R-value insulation do you have in the attic??
Adding some could solve iy,if the ducts are good and the unit is operating properly.
they are r 6.0 ducting but like i said no air leaks so far.