How to measure ducting in HVAC.

Answer Posted / mohammed fayaz

q=av
q= quantity of air (cfm)
V= velocity of air (fpm)
a= area of the room

velocity is =900 from ashrae notes
Ex;

4 tr

1tr = 400 cfm
4tr = 4*400= 1600 cfm

Q = 1600 CFM
V = 900 CFM

Q = AV
A = Q/V
A = 1600/900
1.77 Ft sq
TO convert in mt sq multiple with 0.093
1.77*0.093
= 0.165 mt sq

assume that the duct ht is 0.3
u ll get 55 X 30 cm duct size.
thats it

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