CND-CNF
Centrifugal fans
Product facts
Product and use
Motor installation size
Centrifugal fans of type CND and
CNF are light, compact low-pressure
and medium fans with high
efficiency, low sound level and good
operating economy, designed for
universal installation.
Motor sizes for directly coupled
fans.
Centrifugal fans type CND and CNF
are, due to the choice of material and
finishing, well suited for ventilation
in aggressive environments.
Impeller diameter [mm]
Motor size
315
400
450
500
560
630
710
80 - 112
80 - 132
80 - 132
80 - 132
100 - 160
100 -160
112 - 180
Motor sizes for belt driven fans.
Coverage
Air flow rates from 0.3 to 10 m3/s
and pressure rises up to 4000 Pa.
Installation sizes
CND and CNF are produced in
7 standard sizes with impeller
diameters of 315, 400, 450, 500, 560,
630 and 710 mm.
Construction
Fan housing with rectangular side
panels for universal installation.
The CND and CNF are available in
both directly coupled and beltdriven motor versions.
Temperature range
The CND and CNF are designed for
the temperature range -20 to +70 °C.
Impeller diameter [mm]
Motor size
315
400
450
500
560
630
710
80 - 132
80 - 132
80 - 160
80 - 160
100 - 160
100 -180
112 - 200
Materials
Fan housing: Hot-rolled sheet steel,
Domex 240, in a hot-dip galvanised
version.
Impeller: for types CND and CNF,
the impeller is wide with backwardcurved blades.
Steel quality Domex 500. The
impeller is hot-dip galvanised after
welding.
Flange standard
Motors
Asynchronous standard motors.
Directly coupled: Structural shape
B5 (large flange)
Belt-driven: Structural shape B3
(base motor)
Dimension standard: IEC-72
Electrical standard: IEC-34
Insulation: Class F
Inlet for type CND and CNF in
accordance with Eurovent 1/2.
Corrosion categories
Centrifugal fans of type CND and
CNF are, as standard, for operation
in corrosion category
C5-I (very high) in accordance with
the standard DS/EN ISO 12944-2.
C5-I produces lifetimes of 8-10 years
with hot-dip galvanisation with 6080 µm layer thickness.
Technical classification
The outputs meet the requirements
in accordance with BS 848, 1980
Part 1, installation type D.
2 CND-CNF
Accessories
•
•
•
•
•
•
•
•
Duct bosses
Flexible connections
Mating flanges
Guard nets for inlet and outlet
openings
Anti-vibration mountings
Inspection hatch
Drain plug
Brass inlet funnels
Contents
Product description
4
Dimensions
5
Position designations
7
Motors
8
Dimensioning curves
10
Accessories
17
Sound conditions
20
Regulation of air flow rate
21
Quality and service
22
Important
Patents and trademarks
This document is provided ’as is’. Novenco reserves the right to
changes without further notice due to continuous product development.
Novenco®, ZerAx®,
Novenco A/S.
The fan is designed for continuous operation. The following kinds of
operation may cause fatigue break in the impeller and endanger
people.
The ZerAx® manufacturing processes, technologies and designs are
patented by Novenco A/S.
• Operation in stall area
• Operation with pulsating counter pressure – called pump mode
• Operation with repeated starting and stopping
If in doubt, Novenco should be contacted to assess the suitability of the
fan.
and
are registered trademarks of
Other trademarks appearing in this document are the property of their
respective owners.
Quality and environment
Novenco is certified in accordance with ISO 9001 and 14001.
Copyright (c) 1966 - 2015, Novenco Building & Industry A/S.
All rights are reserved.
MU 14912 0315
CND-CNF 3
Product description
The centrifugal fans type CND and
CNF are light, compact low-pressure
and medium fans designed for
universal installation in compost
plants and greenhouses as well as
light industrial plants in aggressive
environments.
The fans are intended for continuous
operation. The following types of
operation can cause fatigue
breakage of the impeller and thereby
danger of personal injury.
• Operation in the stall area
• Operation with pulsating counter
pressure - pump mode
• Operation with continued
starting and stopping
Novenco should, in case of doubts,
be contacted in order to assess the
suitability of the fan.
Installation sizes
Type CND is produced in 7 sizes
with impeller diameters from 315 to
710 mm, air flow rates from 0.2 to 10
m3/s and total pressures up to
approximately 2000 Pa.
where the CND is partially welded,
the CNF is all-welded and thus
designed for higher operating
RPMs.
Bearing part with two dust-proof
and waterproof deep groove ball
bearings mounted in flanged
bearing housings. The bearings have
lifetime lubrication.
Surface treatment
All the fan parts are protected and
treated with min. 60 µm hot-dip
galvanisation (0.060 mm hot-dip
galvanisation).
Motors
Choice of motor in accordance with
specification.
Requirement: B5 flange (large
flange) for all motor sizes for directly
coupled motors and B3 (base) for
belt-driven motors.
Environment
All CND and CNF fans are designed
for the temperature range -20 to
+70°C.
Type CNF is produced in 6 sizes with
impeller diameters from 400 to 710
mm, air flow rates from 0.2 to 11 m3/
s and total pressures up to
approximately 4000 Pa.
The basic version is designed, with
regard to the choice of material and
finishing, to function in corrosion
category C5-I (very high), see DS/
EN ISO 12944-2.
Construction
Accessories
Centrifugal fans of type CND and
CNF consist of the following main
components.
Duct boss - inlet
Fan housing, constructed from two
rectangular side panels and an allwelded casing.
Is fitted as standard on CND/CNF.
Loose duct bosses are available for
connection of ducts with flexible
connections.
Flexible connections
Inlet funnel, mounted in the front
side panel with a boss for duct
connection and designed to conduct
the air with as little loss as possible to
the impeller.
For duct boss and outlet flange.
Versions (materials) for both circular
(inlet) and square (outlet)
connections.
Impeller type CND and CNF with 8
backward-curved blades designed
and produced with the same
geometry and material. However,
For installation on the fan outlet.
The mating flanges consist of
welded steel frames and are finished
4 CND-CNF
Mating flange
with min. 60 µm hot-dip
galvanisation.
Inspection hatch
CND and CNF are available with an
inspection hatch located in the
casing of the housing.
Inspection hatches are available in 2
sizes, depending on the fan size.
When ordering, please state the
location of the inspection hatch in
relation to the outlet direction.
Drain plug
Please also state the location of the
drain plug in the side panels of the
fan housing in relation to the outlet
direction on order.
Guard nets
Guard nets for the inlet (circular)
and outlet (square) respectively.
Anti-vibration mountings
Types CND and CNF are available
with anti-vibration mountings.
The location and choice of antivibration mountings are shown in
the installation instructions.
Brass inlet funnel
The inlet funnel is available in brass
for both CND and CNF fans for use
in environments with increased
security.
Dimensions
H
K
S
45
B1
B
øD
L
S
F
T
A1
C
A
Sizes
315
400
450
500
560
630
710
S
E
G
S
For anti-vibration mountings øJ
A
A1
B
B1
C
dia. D
E
G
H
dia. J
K
L approx.
S
T
F1
[mm] [mm] [mm] [mm] [mm] [mm] [mm] [mm] [mm] [mm] [mm] [mm]
[mm]
[mm] [mm]
690
800
891
1000
1121
1246
1405
410
485
543
600
673
760
869
595
700
760
850
953
1063
1135
345
400
445
500
560
622
672
252
312
347
392
437
482
537
315
400
450
500
560
630
710
280
340
375
420
465
510
577
ML-24
ML-24
ML-29
ML-29
ML-29
ML-26
ML-31
297
357
392
443
488
533
595
525
585
655
690
795
840
910
11.5
11.5
14
14
14
14
14
335
430
480
535
595
665
750
1040
1120
1175
1255
1440
1525
1620
100
100
125
125
125
125
125
475
540
610
670
780
825
940
1. Dimensions: ML means Motor Length (see motor catalogue)
Weights
Sizes
Weight, directly coupled,
excl. motor [kg]
Weight, belt-driven,
excl. motor [kg]
315
400
450
500
560
630
710
40
59
77
84
113
153
187
62
78
100
118
165
206
255
CND-CNF 5
Outlet flanges
G
P stk. x øR
C
F
A
Connection ducts are made with the
same internal dimensions as the fan
outlet opening (A x B).
MxK
NxT
Mating flanges with the same bolt
holes as the outlet flanges are
available as accessories.
See dimensioned drawing.
B
Sizes
A
[mm]
B
[mm]
C
[mm]
F
[mm]
G
[mm]
K
[mm]
M
[mm]
N
[mm]
T
[mm]
P
[qty.]
R
[mm]
315
400
450
500
560
630
710
315
400
450
500
560
630
710
220
280
315
350
395
440
497
30
30
30
35
35
35
40
347
432
482
536
596
666
750
252
312
347
386
431
476
537
110
140
125
125
125
170
150
1
1
2
2
2
2
3
2
2
2
3
3
3
4
142.5
185
185
155
155
200
170
10
10
12
14
14
14
18
7
7
7
7
7
7
10
6 CND-CNF
Position designations
RD 0
RD 90
RD 180
RD 270
LG 0
LG 90
LG 180
LG 270
LG/1
LG/2
LG/3
LG/4
RD/1
RD/2
RD/3
RD/4
Directly coupled
and low motor
bracket for belt
drive.
Belt drive with
motor mounted on
fan housing.
Positions in accordance with Eurovent seen from motor side
Impeller positions
Pos. LG
Pos. RD
CND-CNF 7
Motors
Motor size1
Sizes
315
400
450
500
560
630
710
- 80
- 90
- 100
- 112
- 132
- 160
- 180
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
1. The motor flange B5 is a large flange and for all motor sizes.
The motor junction box must be coordinated with the fan motor cover.
Max. RPM for CND/CNF
Fan types CND and CNF are
designed and produced with the
same geometry and material, but
where the CND is partially welded,
the CNF is all-welded and thus
designed for higher operating
RPMs.
Sizes
315
400
450
500
560
630
710
8 CND-CNF
Steel quality: Domex 500
Surface treatment: Hot-dip
galvanisation, approximately 60 µm
zinc.
Max. RPM
CND
CNF
4618
3426
2957
2592
2249
2086
1797
5874
4090
3365
2927
2464
2387
1994
Motor installation
The tables show the maximum
motor sizes that can be installed
directly on the fans.
Motor on the side
– vertical motor panel
Motor installation sizes for
directly coupled motors
Fan sizes
315
400
450
500
560
630
710
Motor sizes
Motor on the top
– horizontal motor panel
Belt-driven motor on the top
Belt-driven motor on the side
Fan sizes
–315
–400
–450
–500
–560
–630
–710
80-112
80-132
80-132
80-132
100-160
100-160
112-180
Max. motor
Type
Weights [kg]
112
112
112
132
132
132
132
40
40
40
70
70
70
70
Fan sizes
–315
–400
–450
–500
–560
–630
–710
Max. motor
Type
Weights [kg]
112
112
112
132
132
132
160
40
40
40
70
70
140
140
Low-mounted motor
bracket for large motors
Large motors are mounted on low
motor brackets bolted to the fan
housing. The low centre of gravity
and the large distances between the
installation points produce stable
installation for large motors.
Required motor position and fan
position
Z
W
Shaft end
t
b
ød
l
Fan sizes
ød [mm]
I [mm]
b [mm]
t [mm]
–315
–400
–450
–500
–560
–630
–710
28h6
28h6
38h6
38h6
48h6
48h6
65h6
30
30
50
50
70
70
70
8
8
10
10
14
14
18
31
31
41
41
51
51
69
CND-CNF 9
Dimensioning curves
CND-315
CNF-315
Max.
Ipt
Max.
Ipt
= 5874 RPM
= 0.0951 kg x m2
δ
= 1.20 kg/m3 (at 20° C)
= 4618 RPM
= 0.0951 kg x m2
6000
60
70
65
If the fan is used in the shaded area,
it is necessary to consider in
particular whether the necessary
power can be achieved with the max.
standard motor size.
70
74
74
Pt,
Pa
65
5000
109 dB
4000
60%
Max. speed 618
4
CND
106 dB
3000
4
000
103 dB
0
350
2000
300
500
100 dB
0
97 dB
2
0
0
2 0
Pd
0
Pd + P2
0
P1
30
20
3 m3/s
m/s
2.5
2
1.5
W
0
10
4.5
v
4
0
1
0.5
3
qv
5
0
2.2
1.5
0
7.5
91 dB
6
88 dB
9k
1000
94 dB
40
1000
500
1000
500
50
1500
100
Symbols
Basis for
chart
(Arr. D)
10 CND-CNF
pt
pd
p1
p2
v
=
=
=
=
=
total pressure
dynamic pressure, outlet
connection loss, inlet
connection loss, outlet
air speed, outlet
qv =
n =
η =
kW =
dB =
volume flow
RPM
efficiency in %
power demand, impeller
sound power level, outlet
Pa
Pa
Pa
CND-400
CNF-400
Max.
Ipt
Max.
Ipt
= 4090 RPM
= 0.2440 kg x m2
δ
= 1.20 kg/m3 (at 20° C)
= 3426 RPM
= 0.2440 kg x m2
CNF
CND
5000
60
Pt,
Pa
If the fan is used in the shaded area,
it is necessary to consider in
particular whether the necessary
power can be achieved with the max.
standard motor size.
75
70
65
77
75
77
70
Max. speed 4090
n=
CNF
65
4000
Max. speed 426
3
CND
3000
300
60%
106 dB
0
103 dB
2000
250
100 dB
0
97 dB
0
200
1000
Pd
0
Pd + P2
0
P1
200
40
30
300
400
500
600
500
20
10
m3/s
m/s
4
3
20
100
kW
0
10
6
v
2
1
5
4
0
3
qv
2
0
1
Pd
0
10
9
0
8
7.5
7
150
94 dB
91 dB
30
700
800
900
80
90
1000
40
50
60
70
Pa
Pa
Pa
Symbols
Basis for
chart
(Arr. D)
pt
pd
p1
p2
v
=
=
=
=
=
total pressure
dynamic pressure, outlet
connection loss, inlet
connection loss, outlet
air speed, outlet
qv =
n =
η =
kW =
dB =
volume flow
RPM
efficiency in %
power demand, impeller
sound power level, outlet
CND-CNF 11
CND-450
CNF-450
Max.
Ipt
Max.
Ipt
= 3365 RPM
= 0.4218 kg x m2
δ
= 1.20 kg/m3 (at 20° C)
= 2957 RPM
= 0.4218 kg x m2
CND
CNF
4000
Max. speed = 33
n
CNF
pt,
Pa
65
65 70
60
75
77
77
70
75
65
106 dB
Max. speed 957
2
CND
3000
260
60%
0
103 dB
2000
220
100 dB
0
97 dB
0
180
1000
91 dB
0
10
140
94 dB
qv
0
v
0
Pd
0
Pd + P2
0
P1
1
2
kW
8
6
5
4
0
3
2
1
0
3
3
5 m /s
4
m/s
10
20
100
200
30
300
10000
10
20
400
500
20000
30
40
40
600
700
30000
50
60
12 CND-CNF
pt
pd
p1
p2
v
=
=
=
=
=
total pressure
dynamic pressure, outlet
connection loss, inlet
connection loss, outlet
air speed, outlet
qv =
n =
η =
kW =
dB =
Pa
Pa
70
Symbols
Basis for
chart
(Arr. D)
Pa
volume flow
RPM
efficiency in %
power demand, impeller
sound power level, outlet
CND-500
CNF-500
Max.
Ipt
Max.
Ipt
= 2927 RPM
= 0.6430 kg x m2
δ
= 1.20 kg/m3 (at 20° C)
= 2592 RPM
= 0.6430 kg x m2
CND
CNF
4000
pt,
Pa
Max. speed
CNF
n
92
=2
7
60
65
75
70
79
79
75
70
106 dB
3000
2
Max. speed
259
CND
65
103 dB
220
2000
60%
0
100 dB
180
150
1000
97 dB
94 dB
0
91 dB
0
9
k
11
120
0
Pd
0
Pd + P2
0
P1
4
W
0
3
7
v
2
6
0
1
5
qv
4
0
3
2
1
0
5
6 m3/s
m/s
10
20
100
200
30
300
400
500
Pa
600
500
10
20
30
700
1000
40
50
60
Pa
Pa
70
Symbols
Basis for
chart
(Arr. D)
pt
pd
p1
p2
v
=
=
=
=
=
total pressure
dynamic pressure, outlet
connection loss, inlet
connection loss, outlet
air speed, outlet
qv =
n =
η =
kW =
dB =
volume flow
RPM
efficiency in %
power demand, impeller
sound power level, outlet
CND-CNF 13
CND-560
CNF-560
Max.
Ipt.
Max.
Ipt.
= 2464 RPM
= 1.0212 kg x m2
δ
= 1.20 kg/m3 (at 20° C)
= 2249 RPM
= 1.0212 kg x m2
CNF
CND
60
65
70
80
75
81
81
80
75
Max. speed
4
246
CNF
n=
3000
pt,
Pa
Max. speed
9
CND
224
70
65
2000
190
0
60%
106 dB
160
1000
130
0
103 dB
0
100 dB
97 dB
94 dB
0
91 dB
Pd
0
Pd + P2
0
P1
W
0
9
v
3
8
0
2
7
6
qv
5
4
3
1
0
2
1
0
k
11
10
100
4
7 m3/s
6
5
m/s
30
20
10
100
200
300
400
20
600 Pa
10000
5000
10
500
Pa
30
40
50
Pa
60
Symbols
Basis for
chart
(Arr. D)
14 CND-CNF
pt
pd
p1
p2
v
=
=
=
=
=
total pressure
dynamic pressure, outlet
connection loss, inlet
connection loss, outlet
air speed, outlet
qv =
n =
η =
kW =
dB =
volume flow
RPM
efficiency in %
power demand, impeller
sound power level, outlet
CND-630
CNF-630
Max.
Ipt
Max.
Ipt
= 2387 RPM
= 2.2571 kg x m2
δ
= 1.20 kg/m3 (at 20° C)
= 2086 RPM
= 2.2571 kg x m2
CNF
CND
4000
Max. speed
387
n=2
CNF
pt,
Pa
60 65
70
75
83
80
75
Max. speed
2086
CND
3000
80
83
109 dB
1800
70
65
106 dB
2000
60%
1600
103 dB
1400
1000
100 dB
97 dB
1200
94 dB
1000
0
Pd
0
Pd + P2
0
P1
4
3
kW
v
2
18
0
1
16
qv
14
12
0
10
8
6
4
2
0
5
7
6
3
9
8
m /s
m/s
10
30
20
100
200
300
400
500
600
40
50
60
500
10
20
30
Pa
700 Pa
1000 Pa
70
Symbols
Basis for
chart
(Arr. D)
pt
pd
p1
p2
v
=
=
=
=
=
total pressure
dynamic pressure, outlet
connection loss, inlet
connection loss, outlet
air speed, outlet
qv =
n =
η =
kW =
dB =
volume flow
RPM
efficiency in %
power demand, impeller
sound power level, outlet
CND-CNF 15
CND-710
CNF-710
Max.
IVent
Max.
IVent
= 1994 RPM
= 3.6479 kg x m2
δ
= 1.20 kg/m3 (at 20° C)
= 1797 RPM
= 3.6479 kg x m2
CND
CNF
94
Max. speed
19
=
CNF
n
60 65
70
75
84 84
80
75
80
3000
pt,
Pa
109 dB
Max. speed 1797
CND
106 dB
1600
65
2000
60 %
103 dB
1400
100 dB
1200
1000
97 dB
1000
94 dB
20
kW
18
16
14
12
10
8
6
4
2
0
0
0
v
0
Pd
0
Pd + P2
0
P1
10
20
100
3
m /s
10
5
qv
200
m/s
30
300
400
500
Pa
600
500
10
20
30
700
1000
40
50
60
70
Symbols
Basis for
chart
(Arr. D)
16 CND-CNF
pt
pd
p1
p2
v
=
=
=
=
=
total pressure
dynamic pressure, outlet
connection loss, inlet
connection loss, outlet
air speed, outlet
qv =
n =
η =
kW =
dB =
volume flow
RPM
efficiency in %
power demand, impeller
sound power level, outlet
Pa
Pa
Accessories
Duct bosses
The bosses are available as loose supplies and used for
connection of ducts with flexible connections. They are
standard on both CND and CNF.
Material: Steel
Surface treatment: Hot-dip galvanised, approx. 60 µm
Duct bosses
Flexible connections
The connections are available for duct bosses and outlet
flanges.
Versions in different materials are available for both
flame-proof flexible connections and incombustible
flexible connections.
Material quality: Perl E 6
Temperature range: -30 to +80 °C
Material quality: Alpha Maritex
Temperature range: -36 to +260 °C
Flexible connections
Inlet
Outlet
Mating flanges
The flanges are for installation on the fan outlets. The
constructions are welded steel frames.
Material: Steel Domex 240
Surface treatment: Hot-dip galvanised, approx. 60 µm
Mating flanges
CND-CNF 17
Guard nets
The nets are for the inlet (circular) and outlet (square)
respectively.
Material: Steel wire
Surface treatment: Electro-galvanised, approx. 20 µm
Finish treatment: Passivated
Guard nets for inlet and outlet openings
Anti-vibration mountings
The CND and CNF are available with anti-vibration
mountings.
Refer to the installation instructions for location and
choice of anti-vibration mountings.
Anti-vibration mountings
Base plate for anti-vibration mountings
The CND and CNF are available with base plates for
fixing anti-vibration mountings to the foundation.
Material: Domex 240
Surface treatment: Hot-dip galvanised, approx. 60 µm
Base plate for anti-vibration mountings
18 CND-CNF
Inspection hatches
Material: Domex 240
Surface treatment: Hot-dip galvanised, approx. 60 µm
300
200
The CND and CNF are available with inspection
hatches located in the fan housing.
Inspection hatches are available in 2 sizes and depend
on fan size.
Please state the location of the inspection hatch in
relation to the outlet direction on order.
The location of the inspection hatch and drain boss is
given in relation to the outlet direction.
100
200
120o
180o
Inspection hatch/Access door
Drain plug
Inspection hatch
Drain plug
The location of the drain plug in the fan housing side
panels must be stated on order. The position is in
relation to the outlet direction.
Material: Stainless steel and hot-dip galvanised
fittings respectively
Connection: 3/4” RG
Drain plug
Brass inlet funnels
Inlet funnels made of brass for use in environments
with increased safety is available for CND and CNF.
Material: Half-hard brass
Brass inlet funnel
CND-CNF 19
Sound conditions
Fans in operation generate sound. It
is partly electrical and also
mechanical sounds from the motor,
bearings and other mechanical
parts. Sound from air flows through
fan add to the sound picture as
well.
The sound generation is minimised
by correct design and careful
production of fan parts, in particular
the inlet funnel and impeller, which
contribute greatly to the overall
sound generation. Poor installation
conditions, for example a sharp duct
bend immediately before the inlet
opening, may add considerably to
the sound generation.
Electrical and mechanical generated
sound and the part of sound from
the air flow that passes out through
the fan housing, can only be
dampened by enclosing the fan in a
casing or with walls of low-vibration
materials.
Sound generated in the impeller
spreads through the inlet and outlet
openings to the duct system and on
to the ventilated rooms. Calculation
of the sound conditions in the duct
system and the ventilated rooms,
including dimensioning of any
silencers in the system, is only
possible on the basis of the sound
power level in the fan inlet and
outlet openings. In connection with
all considerations concerning
sound, a sharp distinction must be
made between the two terms sound
power level and sound pressure
level.
Sound power level is an expression
of the energy emitted through the
fan inlet and outlet openings and
forms the basis for any calculation
concerning the sound conditions in
Octave band [Hz]
the connected duct systems and in
the rooms served by the fan.
from the total sound power level
found.
Sound pressure level is a measure of
the sound impression perceived by
the ear at a given location in the
environment. It can be measured
using a sound meter with a
microphone mounted at the
location.
The correction values depend on the
blade frequency
z×n
----------- , where
60
z = number of blades
n = fan speed in RPM
Sound pressure level depends on
the fan sound power level, the
distance from the fan and the
silencing properties of the
environment. When the fan sound
properties are characterised by
stating a sound pressure level, it is
necessary also to give a precise
description of the conditions under
which the stated sound level occurs.
When comparing the sound
properties of two fans, make sure not
to compare the sound power level
with the sound pressure level. Do
only compare sound pressure levels
with the same distances from the fan
and with the same silencing in the
environment.
For a correctly designed fan, the
sound power level depends
primarily on the supplied air flow
rate and the total fan pressure. It can
be read on the graphs for the
individual fans in section
“Dimensioning curves” beginning
on page 10.
The sound power level is stated in
dB with a reference value of 10-12 W,
and applies within the normal
working range of the fan. The
tolerance is ±5 dB. If the sound
power level needs to be divided into
octave values, the sound power level
in the different octave bands is
determined by deducting the
correction values in the table below
63
125
250
500
1k
2k
4k
8k
7
11
13
15
4
7
11
13
7
4
7
10
12
7
4
6
17
12
7
4
22
17
12
7
27
22
17
12
32
27
22
18
Octave band [Hz]
63
125
250
500
1k
2k
4k
8k
Sound power level [dB]
89
93
96
93
88
83
78
73
CND/CNF
Blade
frequency
90-180 Hz
180-360 Hz
360-710 Hz
710-1400 Hz
20 CND-CNF
The CND and CNF have 8 blades
each.
Example
A centrifugal fan of type CND-500
has an output of 3 m³/s at 1600 Pa
and 2323 RPM.
Blade frequency:
2323
8 × ------------ ~ 310 Hz
60
On the graph on page 13, the total
sound power level is 100 dB.
The correction value for 250 Hz is
4 dB.
The sound power level for this
octave band is thus
100 dB - 4 dB = 96 dB
The full octave analysis is shown in
the below table.
Regulation of air flow rate
The fan capacity can be regulated in
several ways, depending on the
operating requirements.
• By changing poles between 2
fixed RPMs in the ratio 3: 2 (motor
with 2 separate windings) or 2:1
(Dahlander winding motor)
• By frequency regulation
• By a combination of the above
Changing poles
In connection with time-related
variations in the air flow rate
demand, for example night-time and
daytime operation, it is
recommended that the fan is fitted
with a change-pole motor. When the
fan is changed to a different RPM,
the fan efficiency is unchanged.
The change can be timer-controlled.
If other operating points are
required, than can be achieved by
changing poles, other regulation
methods must be used.
Frequency regulation
Fan efficiency remains virtually
unchanged throughout the
regulation range and no sound is
generated as a result of the
regulation.
CND-CNF 21
Quality and service
Rest assured
Warranty
The Novenco CND-CNF centrifugal
fans are produced in accordance
with Novencos well-known quality
standards. Novenco is ISO 9001
certified and all fans are inspected
and tested, before leaving the
production.
The fans are offered with options for
technical guidance on installation,
test of function and training of
personnel.
Novenco provides according to law
a standard 12 months warranty from
the product is sent from the factory.
The warranty covers materials and
manufacturing defects. Wear parts
are not covered.
Extended warranties can be agreed
upon.
CND-CNF 22
MU 14912 0315
Novenco develops and manufactures
ventilation systems that are marketed
worldwide through subsidiaries and
agents.
The company was founded in Denmark
1947 and has become one of the
world-leading suppliers.
Novenco symbolises quality
and environmentally responsible operation and is certified according to ISO 9001
and ISO 14001.
The company headquarters are located in
Naestved, Denmark.
and
are
Novenco, ZerAx,
registered trademarks of Novenco A/S.
Read more about Novenco on the
internet.
Novenco Building & Industry A/S · Industrivej 22 · 4700 Naestved · Denmark
Phone: +45 70 77 88 99 · www.novenco-building.com