Trane TRG-TRC014-EN manual period four, System Resistance Curve, Fan Modulation

period four

Fan Modulation

notes

plot performance on the basis of the static pressure component only. Performance curves published for some packaged air handlers will include the effects of the dampers, filters, and coils that are in the unit. In this case, the static pressure capacity of the fan must be able to overcome the rest of the static pressure losses in the system (supply duct, terminal units, diffusers and grilles, and so forth).

To deliver 24,000 cfm [11.3 m3/s] of air, this example fan, running at 1,000 rpm, generates 2.7 in. H2O [672.5 Pa] of static pressure.

System Resistance Curve

static pressure

system resistance curve

2.7 in. H2O

[672.5 Pa]

1.05 in. H2O

[261.5 Pa]

15,000 cfm	airflow	24,000 cfm	Figure 73
[7.1 m3/s]		[11.3 m3/s]

System Resistance Curve

The system resistance curve is a plot of the pressure drop, in terms of static pressure, that the system (including the supply ductwork, duct fittings, terminal units, diffusers and return grilles, coils, filters, dampers, and so forth) creates over a range of airflows. When the airflow in a system increases, the resistance also increases because more friction is experienced.

When delivering 15,000 cfm [7.1 m3/s], this example system creates 1.05 in. H2O [261.5 Pa] of static pressure resistance.

TRG-TRC014-EN 53