M23740N6-03 01/10/07
page
18
AIR FLOW CHECK
The effective unit flow-rate is function of the aeraulic
system characteristics.
It is so necessary to check the air flow-rate and eventually
to proceed with the appropriate calibrations on the system
(dampers, diffusers etc) and on the unit (fan speed control,
pulley calibrations etc in base of the unit type and its
configuration). Before performing the check, make sure that
the system has been completed in all its parts (derivations,
dampers, grilles, diffusers etc) .
Pa
L/sec
1
2
3
B
A
C
D
D = unit head-flow rate curve
A = system calculated curve
1 = project theorical working point
3
= if the system has pressure drop lower than the project
ones, the working point will be the 3,with flow-rate
higher that the project one
2
= if the system has pressure drop higher than the project
ones, the working point will be the 2, with flow-rate
lower that the project one
In the time the working point can change, for example for
the operations on the system (grilles covered by furniture,
closed outlets to modify the air diffusion, exclusion or
addition of the distribution sections etc.) or for lacking
maintenance (clogged air filters, blocked dampers etc) .
