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38 TRG-TRC013-EN
notes
period two
Fan Types
The selection of the type of fan to be used in a particular application is based on
the system size and space availability.
The forward curved fan is best applied in small systems requiring 20,000 cfm
[9.4 m
3
/s] or less and static pressures of 4 in. H
2
O [996 Pa] or less. The FC fan is
also the least costly.
On the other hand, systems requiring in excess of 20,000 cfm [9.4 m
3
/s] and
3in. H
2
O [747 Pa] of static pressure are usually best served by the more efficient
backward inclined or airfoil fans. With larger fan sizes and larger motors, the
higher fan efficiencies can result in significant energy savings.
When space is a prime consideration, the vaneaxial fan may be the best
solution. Straight-through airflow permits this fan to be installed in limited
space.
Finally, the VPVA fan is generally applied in large, built-up systems requiring
airflows in excess of 50,000 cfm [23.6 m
3
/s] and greater than 3 in. H
2
O [747 Pa]
of total pressure.
Fan Selection
▲ Forward curved (FC)
◆ Lower airflow, lower static pressure, lower first cost
▲ Backward inclined (BI) or airfoil (AF)
◆ Higher airflow, higher static pressure, higher efficiency
▲ Vaneaxial
◆ Limited space
▲ Variable-pitch vaneaxial (VPVA)
◆ Large systems, higher airflow
Figure 57