they put what looks like bubble wrap with aluminum foil on both sides of it on the inside of it. the intake is only about 6 inches long
Originally Posted by furnacemaninc
boy i love lack of return air and excessive fpm across filter grill
im not a pro but i think i have a lot of return air. i have a 14x25 on the side of the furnace and 4 6inch in the bottom of the furnace. what is fpm
Originally Posted by dezerttech
FPM is a measure of velocity...in this case air velocity in feet per minute (speed of air).
Originally Posted by chrism9232
Where CFM is a measure of volume in Cubic feet per minute (amount of air).
If you know one of these and the square feet of duct area the air is traveling through....you can calculate the other.