I am using the duct sizing guide at https://airhand.com/designing/ to size our ducts appropriately. I have identified our 'main' machines and have increased the ducts appropriately as these main machines enter the main trunk.

My issue/question is that we have a corner of our shop that contains only one 'main' machine but contains 4 other non-main machines. Each of these machines has a 4" port. The way I currently have the system designed, the one main machine in this corner connects to the trunk and the trunk size increases at that point. But the 4 other machines in this corner tie into this main machine's branch and the duct DOES NOT increase in diameter. If I'm reading that sizing guide correctly, this is what we're supposed to do. The duct only increases in size when a main machine enters the trunk. If I am reading that guide correctly, and I have 5, 4" machines all feeding into one little 4" duct, that seems like a lot for that duct to handle. Granted, we will only be using at most 3 of them at once, but even so, it seems like a lot for it to deal with.

So should we increase this duct to 5 or more inches to accommodate the multiple machines that feed into it? But then I worry that we won't have a high enough CFM due to the increased duct size.

I'm probably making this more complicated than it needs to be, but we're dropping $5k+ on our little dust collection system and I want to make sure we do it right.