Parallel Fan Operation; Motor And Drive Selection; Maximum Torque For Operation Of Inlet Vanes; Selecting Model Q Fans In Parallel - Trane Fan User Manual

Table A-3 — Maximum Torque For
Operation Of Inlet Vanes
Control Opening
Arm Torque
Size Class (In.) (In.-Lb)
1 8
16 2 8.75 14
3 23
1 12
19 2 8.75 21
3 34
1 17
21 2 8.75 31
3 32
1 26
24 2 8.75 48
3 79
1 37
27 2 8.75 66
3 109
1 52
30 2 8.75 94
3 155
1 65
33 2 8.75 128
3 212
1 100
36 2 10.81 180
3 298
1 138
40 2 10.81 249
3 412
1 193
44 2 10.81 349
3 576

Parallel Fan Operation

The Q fan performance curve has a
characteristic shape where two
different cfm's are possible at the same
static pressure. Therefore, when
selecting fans for multiple installation
connected with either a common inlet,
a common discharge or both, care
must be taken to eliminate the
possibility of fan paralleling.
Figure A-7 shows two typical cfm-sp
performance curves for the Q fan. Fan
paralleling can occur when multiple
fans are selected in the shaded area.
The shaded area is determined by
going straight across from the lowest
point of the fan performance curve at
the left of the surge line (A and A
the same curve to the right of the surge
line (B and B ). Points B and B
1
constant system curve.
Application
Considerations
Table A-4 defines this constant
system curve as a percent of wide-
Closing
open cfm. If fans in parallel are
Torque
always operated to the right of this
(In.-Lb)
constant system curve, fan paralleling
7
13 will not occur.
22
Table A-4 — Parallel Operation
11
19
31
Fan Size
15
26
16
44
19-21
20
24-30
36
33-44
61
49-60
27
48
79
35
63
Figure A-7 — Selecting Model Q Fans in Parallel
104
41
81
134
59
106
175
75
136
225
99
179
295
Recommended Q Fan Configuration Inside an Air Handler
) to
1
fall on a
1

Motor and Drive Selection

The Model Q fan has been designed for
use with NEMA "T" Frame
motors. Motor hp limits for Class I, II,
and III construction are listed in the
roughing-in Dimensional Data section
of this catalog.
Minimizing belt tension forces
Minimum % of WOCFM
For Two Model Q Fans
increases bearing life and reduces fan
In Parallel
noise. The Q fan and Super Q II fan
80% WOCFM
drive selection is totally computerized
81% WOCFM
by the factory to achieve quiet, long life
83% WOCFM
operation. If Trane provides Q fan
73% WOCFM
drives, all fan motor information must
85% WOCFM
be made available to the Trane sales
engineer.
Side View
18