CNA-CNB
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Novenco Centrifugal Fans CNA and CNB September 2007

Product Facts Single-inlet low-pressure fans with backward-curved blades. In industrial ventilation systems for max. 70° C, where a low sound level is required. The M-type for corrosive CNA: 9 installation sizes with impeller diameters from 250 mm to 1000 mm. Air flow rates from CNB: 7 installation sizes with impeller diameters from 400 mm to 1000 mm. Air flow rates from 0.8 Fan housing with rectangular side panels for universal installation. The fan is available in directly coupled Surface treatment Housing, CNA/B: Sendzimir galvanised (hot-dip galvanised) sheet steel, unpainted. Housing,...

Novenco Centrifugal Fans Regulation of Air Flow Rate 16

Centrifugal fans of type CNA and pressure fans, designed for universal installation in light industrial plants. Type CNA is produced in 9 sizes with impeller diameters from Type CNB is produced in 7 sizes with impeller diameters from 400 mm to RPMs with air flow rates from 0.8 Centrifugal fans of type CNA and CNB consist of the following main Fan housing, constructed from two rectangular side panels and a casing. Inlet funnel, mounted in the fan's front side panel with a boss for duct connection and designed so that the air is conducted without loss to the Impeller with wide, backward-...

Position Designations Please note: Fan positions in connection with installation on a common base frame must be indicated in accordance with EUROVENT. Directly coupled: motor installed on fan housing low motor bracket for belt drive Positions in accordance with EUROVENT seen from the motor Continuous product development at Novenco may result in changes being introduced without prior notice.

Dimensioned Drawings Directly coupled: With belt drive: *Weight excl. motor and belt drive Outlet Flanges Mating flanges (4 rails) with the same bolt holes as the outlet flanges are Ducts are made with the same internal dimensions as the fan's outlet opening See dimensioned drawing above. Continuous product development at Novenco may result in changes being introduced without prior notice.

Motor installation The tables show the maximum motor size that can be installed - vertical motor panel - horizontal motor panel Motor Sizes Directly coupled Large motors are installed on clamp rails beside the fan. A common base shown in the drawings, is available. Please state the desired motor Continuous product development at Novenco may result In changes being introduced without prior notice.

Shaft end for belt drive Flexible connection, outlet Drain plug Inspection hatch with inspection hatches in the housing's casing and with drain When ordering, please state the location of the inspection hatch and drain boss in relation to the outlet For example: Inspection hatch Flexible connection, inlet Duct boss Continuous product development at Novenco may result in changes being introduced without prior notice.

flow rate and the pressure loss in the ventilation system in question = the fan's static pressure, ps = ps2 - psi- To establish the fan's total pressure pt, add the air's speed pressure, the dynamic pressure pd at the outlet and the installation loss at These values are stated in connection with the dimensioning A dimensioning example is shown dimensioning graphs refers to the fan shaft. To cover the loss in the belt and bearing part, etc., the power consumption reading is increased by (ducts for the inlet and outlet). Pressure loss = static pressure = ps = The graph on page 11 shows that...

Dimensioning Curves Circumferential speed Circumferential speed pd = dynamic pressure, outlet Pi = connection loss, inlet p2 = connection loss, outlet kW = power demand, impeller dB = sound power level, outlet Continuous product development at Novenco may result in changes being introduced without prior notice.

Dimensioning Curves Circumferential speed Circumferential speed pd = dynamic pressure, outlet PJ = connection loss, inlet p2 = connection loss, outlet kW = power demand, impeller dB = sound power level, outlet Continuous product development at Novenco may result in changes being introduced without prior notice.

Dimensioning Curves Circumferential speed Circumferential speed pd = dynamic pressure, outlet Pi = connection loss, inlet p2 = connection loss, outlet kW = power demand, impeller dB = sound power level, outlet Continuous product development at Novenco may result in changes being introduced without prior notice.

Circumferential speed pd = dynamic pressure, outlet n Pi = connection loss, inlet 0 p2 = connection loss, outlet kW : volume flow power demand, impeller sound power level, outlet Continuous product development at Novenco may result in changes being introduced without prior notice.

Centrifugal Fans CNA and CNB Dimensioning Curves CNA-1000 = 785 RPM ρ = 1.20 kg/m3 Iv = 14 kgm2 pt, Pa max. CNB-1000 max. = 960 RPM ρ = 1.20 kg/m3 Iv = 14 kgm2 Circumferential speed = 0.052 x n, m/s. Basis for chart (Arr. D) Da D1 1 x D1 14 CNA 3 x Da u Symbols pt = total pressure pd = dynamic pressure, outlet p1 = connection loss, inlet p2 = connection loss, outlet v = air speed, outlet qv = n = 0 = kW = dB = volume flow RPM efficiency in % power demand, impeller sound power level, outlet Continuous product development at Novenco may result in changes being introduced without prior notice.

Sound Conditions When a fan is operated, sound is generated. This is partly electrical and mechanical sound in the motor, bearings and other mechanical parts, partly air sound that occurs as the air Sound generation is counteracted by the correct design and careful particular the inlet funnel and impeller, where air sound is concerned. In this connection, it must be noted that poor installation conditions, for example a sharp duct bend immediately before the inlet opening, may increase sound generation considerably. The electrical and mechanical sound, and that part of the air sound that...

Regulation of Air Flow Rate requirements, the fan's capacity can be regulated in several ways: - By changing poles between 2 fixed RPMs in the ratio 3: 2 (motor with 2 separate windings) Changing Poles In connection with time-related variations in the air flow rate demand (for example, night-time recommended that the fan be fitted with a change-pole motor. When the the fan's efficiency is unchanged. If other operating points are required than can be achieved by changing poles, other regulation methods must be used. Frequency Regulation The fan's efficiency remains virtually unchanged...