Trox VFL - Quick Sizing; Volume Flow Rate Ranges and Upstream Conditions

04/2014 US K5 – 2.1 – 6
Quick sizing VFL
Upstream conditions
The volume flow rate
accuracy Δ applies
to a straight upstream
section of the duct.
Bends, junctions or a
narrowing or widening
of the duct cause
turbulences that may
affect measurement.
Duct connections, e.g.
branches off the main
duct, must comply with
EN 1505. Some
installation situations
require straight duct
sections upstream.
Free air intake only with
a straight duct section
of 1D upstream.
A bend with a curvature radius of at least 1D – without
an additional straight duct section upstream of the
volume flow limiter – has only a negligible effect on
the volume flow rate accuracy.
A junction causes strong turbulences. The stated volume
flow rate accuracy Δ can only be achieved with a straight
duct section of at least 1.5D upstream. Shorter upstream
sections require a perforated plate in the branch and
before the volume flow limiter. If there is no straight
upstream section at all, the control will not be stable,
even with a perforated plate.
Bend
D
1
D
Junction
1,5D
D
1.5D
Nomenclature
 CFM: Flow rate

NOM
CFM: Nominal flow
rate
∆ p
g
in. w.g.: Total pressure
differential
Volume flow rate ranges
The volume flow limiters
are factory set to the
reference volume flow
rate 
ref
. Customers
can then simply set the
required volume flow rate
(setting values 1 to 11
with the exception of size
150).
Available volume flow rate setpoint values [m
3
/h]
Size
100 (4")
125 (5")
150 (6")
200 (8")
250 (10")
Pos 1 2 3 4 5 6 7 8 9 10 11

nom
  
m
3
/h 18 24 33 39 48 58 71 79 92 105 122 122
l/s 5 7 9 11 13 16 20 22 26 29 34 34
cfm 11 14 19 23 28 34 42 47 54 62 72 72
m
3
/h 39 48 58 69 82 98 113 131 150 171 195 195
l/s 11 13 16 19 23 27 31 37 42 48 54 54
cfm 23 28 34 40 48 58 67 77 89 101 115 115
m
3
/h 50 - 85 - 120 - 160 - 205 230 265 265
l/s 14 - 24 - 33 - 44 - 57 64 74 74
cfm 30 - 50 - 70 - 95 - 120 135 155 155
m
3
/h 94 127 166 207 253 297 343 391 436 481 529 529
l/s 26 35 46 58 70 83 95 109 121 134 147 147
cfm 55 75 98 122 149 175 202 230 257 283 312 312
m
3
/h 159 215 278 337 399 473 519 574 632 705 764 764
l/s 44 60 77 94 111 131 144 160 175 196 212 212
cfm 93 126 164 199 235 278 306 338 372 415 450 450
Volume ow setpoint values
Reference ow rate