New here, I'm hoping for some help with this question. I recently bought a single story house, 2000 sq ft (8' ceilings) and central AC had been installed about 20 years ago. However, they didn't include vents into the bathrooms (2) or a screened in porch was that was subsequently converted into a room (150 sq ft) and has no AC vent. The AC system is 3 ton and I'm trying to figure out what the CFM is based on the install manual (a rule of thumb is 400 CMF per ton). As I understand it, I may be able to add outlets to the main trunk for these rooms (say 200 sq ft total) but need to have some minimum CFM per room. The house currently has 7 vents supplying the cool air and all are flexible 7" diameter ducts off the main trunk. So if total CFM is 1200, that's 171 CFM per vent. If I added 2 more vents (1/2 size for each bathroom), it would bring CFM down to 133 CFM. Is that asking for trouble? House is in SW CT.
The evaporator unit is an FCX3600C1 and the documentation is attached. I think pg. 3 is concerning airflow volume but I'm not sure what 'SP IN. WG.' means or what the voltage is referring to in the table.
Without knowing the entire laying out of the duct system, you can't get a proper answer.
SP IN WG is Static pressure inches in water gauge. It's the important measurements we use to determine if duct size is too small, too big, or something is restricting the system of air. As the static pressure increases, the air flow decreases. That's why as the static number increases, it corresponds to a lower CFM value across the chart.
The voltage is showing you the differences you'll experience with the airflow in relation to whether your unit is running off a 208v power supply, or a 230v power supply since it's compatible to run on either.
You can see you can move more air with 230v instead of 208v. You are likely on 230v. 208v is often seen when it's installed in commercial, or some condo/apartment buildings.
Thank you Porcupinepuffer for the response. I will make some measurements and sketch up the system. I'm pretty sure the voltage is 230 (single family home). Where is the static pressure measured for such tables? I do understand Bernoulli's principal where as velocity of a fluid increases, pressure decreases, so that makes sense.
I discovered that the system only has 14" round flex duct (around 15 feet long, with bends) feeding the unit return air. I know that's not good. From what I've read, that may be limiting CFM to 700 CFM... The duct exisitng duct routing looks far less than optimal, with a sharp bend near connection flange, so it may be even worse - (I guess I can't post photos yet). So it seems I should add another return and try to improve the duct routing before anything else. In order to do that, I have to somehow merge the two returns to the unit and am not having much luck finding ductwork suited to doing that. It appears that the existing hookup of flex duct to the unit uses a transition piece that has the 14" round flange on an insulated sheet metal box measuring 20 x 21.5 cross section x 14" length that attaches to end of unit. Would it be easiest to put a T in the existing flex duct to bring in the 2nd return (assuming I can find a 14" T)?