where or how do you find out what size of ducts is need for a ac/heating, what is formula?

Answer 1

Go to http://www.mcquay.com/McQuay/DesignSolutions/Software and download and unzip the Ductsizer program.
Figure 400 CFM/ton of air conditioning.
I figure my supply ducts at around 1000 FPM or less if possible (duct gets bigger) and size return ducts for 800FPM or less if possible. This gives less restriction and lowers the air noise.
After you open the program, punch in the CFM and the FPM and one of the duct dimensions and it will give you the other dimension.

By the way Kyla, you're hot.

Answer 2

Sizing ducts for the ac/heating is fairly complicated. because you need to know the volume of air, distance from the air handler to each of the outlets, including all turns and diffusers and tees all of which will need to be taken into consideration. Another factor is noise the smaller the duct the higher velocity the nosier it is.
Also fan in the airhandler has limited capacity. If you install duct with to high pressure loss you will get less air and that in turn means you will have less heat or cold air.
If you never did it you will get better if you get a free estimate usually large places like Home Depot will give you an estimate.
Good luck.

Answer 3

I tell a lot of people this

1-800-79-DEPOT

they will tell you how to do everything and even come and give you a free estimate...even if you dont use them you will have the information you need to do it yourself