Quote Originally Posted by skizot View Post
I know, I need to retest the static on Med/Hi, but I don't own my own manometer. I assume the static will probably be higher on a higher speed, so the 1592 CFM on Med/Hi for 0.8" is probably not 1592, but less. How much less I'm not sure of until I have it measured again, but I'm sure I'll still be over 800 FPM, easily. 800 FPM is 1333 CFM (given my dimensions), which is less than what I get on Medium with a measured static pressure of 0.8.

BTW, the ESP is definitely 0.8" W.C. on Medium. The tech that was out the other day verified this.

I think if you were moving the air across the coil that fast you see other problems.

You asked before about velocity's across the coil and the 300 to 400 number sounds OK ballpark, but that is not how the manufactures rate them. They do testing to an ARI standard that is making sure they maintain a minimum FPM that is a ratio from capacity to CFM. That kind of math makes my head hurt, so I stick to looking at the proper duct design and the units fan will move the air at the proper speed if I set it up right.

Do you have a slab coil? Or is it an N or a A? The shape matters if you want to do the math to estimate the velocity. I find it easier to just measure it myself.