Quote Originally Posted by como View Post
The original Manual D called for all duct work to be run in sheet metal. It was all ran in air connector (not air duct) and is loose, each run is compressed in multiple places etc. It is supposed to be checked this week for CFM at each supply register, and I'm being told if each supply register is the correct CFM then the system is working fine and they are done.
This is a great thread, all good comments, thanks for starting it.

I like the idea of new rules of thumb. Rules of thumb will never go away. Seems pretty widely accepted by experienced knowledgable contractoer that old rules of thumb cause fear of deviation that leads to gross oversizing.

Stuffy? What's the house cfm50 leakage rate? Do you have a erv or some type of fresh air system? Don't blame your hat for your wet feet.

Here are just a couple problems with cfm at register. First, what IS the correct cfm? Was it in your design plans, or will it be a verbal "yep, that looks about right.".

Second, how does this address static? (this problem probably includes insufficient filter- udarrell - how many sq inches need?)

They don't hook garden hoses to a fire truck for a reason. Doesn't matter how much you turn up pressure if you don't have the volume. A hose that is designed for 1-5 gallons per minute just won't take 50. And if the need is for 1-5 gallons per minute, does it make sense to change the hose? A bigger hose will just kill all the plants.

Unfortunatly the solution is likely to change for 50gpm pump to 5 gpm pump. Might see what deal they'll give on a trade to a 3 ton GREENSPEED.