Carrier Aero 39MN Series Installation, Start-Up And Service Instructions Manual page 134

a39-4178
ENSURE ADEQUATE
HEIGHT/CLEARANCE
FOR DRAIN TO FLOOR
Fig. 106 — Condensate Drain, Blow-Thru
Trapping (All Sizes)
MIXING
BOX
Return Clean
MXB
Duct Filter
0.4 in. wg
0.5 in. wg 0.2 in. wg
Fig. 107 — Draw-Thru Example
TYPE
FORWARD-CURVED (FC) • Double-width, double-inlet (DWDI) construction.
SIDE VIEW • Best at low or medium pressure (approximately 0 to 5 in. wg).
• Horsepower increases continuously with increase in air quantity (overloads) as
• Less expensive than AF fans.
• Runs at relatively low speed, typically 400 to 1200 rpm.
• Blades curve toward direction of rotation.
AIRFOIL (AF) • Double-width, double-inlet (DWDI) construction.
SIDE VIEW • Best in high capacity and high-pressure applications (4 to 8 in. wg).
• Horsepower peaks at high capacities.
• Most expensive of centrifugal fans.
• Operates at high speeds, typically 1200 to 2800 rpm. About double the speed of
• Blades have aerodynamic shape similar to airplane wing and are curved away
PLENUM (PAF) • Single-width, single-inlet (SWSI) construction.
END VIEW • Characteristics similar to DWDI airfoil fan.
• Blades have aerodynamic shape similar to airplane wing and are curved away
P + 1/2"
1
1/2"
MINIMUM
H
C
E
O
A
O FAN
T
L
Heating
Cooling
Coil
Coil
0.2
1.2 in. wg
in. wg
Table 35 — Fan Type and Application
CHARACTERISTICS
static pressure decreases.
FC fan for similar air quantity.
from direction of rotation.
from direction of rotation. Fewer blades and wider blade spacing than AF fans.
MIXING
BOX
Trap Against Static Pressure Downstream of Fan - Static Pressure
2.3 in. wg - 1.2 in. wg = 1.1 in. wg
Fig. 108 — Blow-Thru Example
134
C
PLENUM
O
FAN
O
L
Static Pressure Between the Fan Static Pressure Between the Fan
and Drain and Drain
(Coil and Plenum Section) (Coil and Plenum Section)
1.2 in. wg 1.2 in. wg
External Static Pressure
Downstream of Fan
2.3 in. wg
Between Fan and Drain =
APPLICATION
For low to medium pressure
air-handling applications.
For medium to high air capacity
and pressure applications.
Best in applications with limited
space or multiple ducts.