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3-26. Increasing the Fan Speed
If external static pressure is too great (due to long
extension of ducts, for example), the air flow volume
may drop too low at each air outlet. This problem may
be solved by increasing the fan speed using the
following procedure:
(1) Remove 4 screws on the electrical component
box and remove the cover plate.
(2) Disconnect the fan motor sockets in the box.
(3) Take out the booster cable (sockets at both
ends) clamped in the box.
(4) Securely connect the booster cable sockets
between the disconnected fan motor sockets in
step 2 as shown in the Fig. 3-85.
(5) Place the cable neatly in the box and reinstall
the cover plate.
Booster cable
Booster cable
Electrical component box
(At shipment) (Booster cable installed)
0491_M_I
Fan motor socket
Fan
motor
Fig. 3-85
Indoor Fan Performance
24 Type
36 Type
Fig. 3-86
■ How to read the diagram
The vertical axis is the external static pressure (Pa) while the horizontal axis represents the AIR FLOW (CFM).
The characteristic curves for “HT”, “H”, “M” and “L” fan speed control are shown.
The nameplate values are shown based on the “H” air flow. For the 24 type, the air flow is 636 CFM, while the
external static pressure is 49 Pa at “H” position. If external static pressure is too great (due to long extension of
duct, for example), the air flow volume may drop too low at each air outlet.
This problem may be solved by increasing the fan speed as explained above.
NOTE
HT : Using the booster cable
H : At shipment
900
Air Flow (CFM)
External Static Pressure
0
50
0
0.1
0.2
0.3
0.4
0.5
150
700500300
Limit line
L
100
1982_U_I
H
HH
(Pa)
(inAq)
Limit line
HT
Air Flow (CFM)
External Static Pressure
0
50
0
0.1
0.2
0.3
0.4
0.5
0.6
0.8
150
200
500 1000
Limit line
L
H
HH
HT
100
1983_U_I
(inAq)
(Pa)
Limit line
18 Type
1981_U_I
400 500
Air Flow (CFM)
External Static Pressure
0
50
0
0.1
0.2
0.3
0.4
0.5
150
200 300
Limit line
L
100
HT
(inAq)
(Pa)
Limit line
HH
H
12 Type
1980_U_I
200 300
Air Flow (CFM)
External Static Pressure
0
50
100
0
0.1
0.2
0.3
0.4
0.5
150
400
(Pa)
Limit line
HT
H
HH
L
Limit line
(inAq)