I need to talk through something else here - JPA's assistance may be required... The air handler is rated 1240 CFM, 30,000 BTU/hr
The heat pump has similar specs; it's 2-ton instead of the 2.5-ton of the air handler. 23,000 BTU/hr, and if I'm reading this table correctly, should be matched to an AHU at 860 CFM.
My first reaction there is that it seems the AHU I have should somehow be limited to low fan. (960 CFM from the AHU to match the 860 CFM recommended for the heat pump) I spoke with the HVAC repair guy the other day, who said that if the blower in my AHU was to be run at multiple speeds that there would be a provision for that on the control board, but there isn't - so he says. Can anyone speak to that?
The real reason for this post is I'm trying to figure out how large the supply registers need to be.
They'll come through the face (or theoretically the bottom if better) or the soffits - one on each side near the screen. The maximum height is about 6 inches, and the maximum length is about 36 inches.
The theater has 2x 6" flex duct supplies. JPA's field sizing chart estimates each 6" round duct can supply 75 CFM. My air handler has 6x 6" flex ducts feeding from it, 2 to the theater and 4 elsewhere. If they were all the same length and shape, they would all move the same volume of air. Of course, they're not, so how do I go about estimating the volume through the theater ducts? Short of taking the approach that I'll have to tweak the register size, which I can make peace with ultimately - what's the data I need to figure this? If I had the volume through each duct, I could figure the face velocity through a given register - right? But is there another way? Maybe I should just assume 75 CFM in each duct, and shoot for 250 fpm based on that.
I know that most of the registers in the basement are unacceptably loud, and whatever standard size is (6x10?). It seems that the length of the ducts to the theater, which are the longest aside from the duct to the bathroom, which is very quiet and the same register as the others, would keep the registers quiet in the theater, but obviously I'd like to be sure. I can close off other registers to improve flow into the theater if I need to, so if volume is down in the long theater ducts, I can improve that after the fact.