duct size calulation

[sniperbusch]

Quick search did not yield base line calulations; installing 2 new duct trunk runs for a new 100 MBTU / 3.5 ton system. Delivers 1974 CFM for cooling and need to evaluate return. Duct design is my weak area and thanks.

[Samurai Appliance Repair Man]

Try this duct size calcumulator:

http://www.hvacbooks.com/duct_calculator.htm

More meat n' taters on the system design in this Google book.

[sniperbusch]

I did come across the calcumulator but required a password. Your link does not do anything either.  I do have a Trane Ductulator but requires friction loss. Thanks anyway.

 

[Samurai Appliance Repair Man]

Friction loss? Why didn't ya say so! This udder calcumulator will hepya with that:

http://www.freecalc.com/ductfram.htm

[sniperbusch]

That is a sweet (wanted to say bad ass) calcumulator, thanks.

I did happen across this one that I used to cross reference:

http://efficientcomfort.net/jsp/ResDuct_Web.jsp

I used 0.1"wc/100ft, a streamlined sizing model from Standex for a ball park figure and inputed the Residential Air Duct Sizer and Velocity Calculator for a 45,500 Cooling BTU system at about 15000 CFM. I am leaning towards 30 or 32  by 8 trunk. I will use your calcumlator after I can obtain more information to fine tune the system and print out same for reference. I am still unclear on the friction rate as it effects the duct sizing until I can factor in the whole system, thanks!