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TRG-TRC013-EN 19
period one
Fan Performance
notes
By plotting several such points, a curve can be established. This system
resistance curve represents the static pressure that the fan must generate, at
various airflows, to overcome the resistance—or static-pressure loss—within
this particular system.
Fan – System Interaction
By superimposing the system resistance curve on a fan performance curve, the
intersection predicts the airflow and static pressure at which the fan and system
will balance—design operating point A.
If the installed system resistance is different from that assumed during the
design process, the fan-and-system balance point—the operating point—will
not be as intended. This means that the fan and system will balance at a point
that has a higher or lower airflow, static pressure, and input power.
airflow
airflow
static pressure
static pressure
3,500 cfm
3,500 cfm
[1.65 m
[1.65 m
3
3
/s]
/s]
0.65 in. H
0.65 in. H
2
2
O
O
[159 Pa]
[159 Pa]
2,000 cfm
2,000 cfm
[0.94 m
[0.94 m
3
3
/s]
/s]
2.0 in. H
2.0 in. H
2
2
O
O
[491 Pa]
[491 Pa]
system
resistance
curve
system
system
resistance
resistance
curve
curve
System Resistance Curve
Figure 28
airflow
airflow
static pressure
static pressure
design system
resistance curve
design system
design system
resistance curve
resistance curve
$
Fan – System Interaction
surge
region
surge
surge
region
region
Figure 29