Trane TRG-TRC013-EN manual cwt t, e eK/ up”

g
			surge region			design system
						resistance curve
							input power
pressure				%
					$
total	VAV system		&
	modulation							55º
	curve
								50º
							45º	e)
						40º		(angl
								tch
				25º		35º	pi
	15º	20º			30º		ade
							bl	g MG
					airflow
cwt °t
.e_eK/ up” x

Again, as the system resistance curve shifts upward and the fan begins to “ride up” the current blade pitch curve toward f, from its design operating point e, it delivers a lower airflow at a higher total pressure. The system static-pressure controller senses this higher static pressure and sends a signal to the fan, instructing it to change the pitch of the fan blades. This causes the performance curve for the fan to shift downward until the balance point g falls along the VAV system modulation curve and the fan satisfies the system static-pressure controller.

The advantage of variable-pitch blade control is its broad modulation range— from design airflow to virtually zero airflow—plus its potential for energy savings.

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