Centrifugal Fans

High efficiency M08-

The high-efficiency ERS/DRS centrifugal fans have been developed for use in modern ventilation and air conditioning applications and are well suited to move air and lightly aggressive gas and vapours.
The size comply with standard R20 in accordance to DIN 323.
The designation of size corresponds to the outside diameter of the impeller.

The casing is manufactured from galvanised sheet steel. Side plate and scroll plate are joined together by a rolled seam. Mounting brackets can be fitted to the fan side plate in steps of 90°.

The centrifugal impeller is made of galvanised sheet metal and is fitted directly to the external rotor motor. The motor-impeller-unit is balanced in two plains according to G 2,5 (DIN ISO 1940).

Electrical connection
Motors come with flying lead. The electrical connection is made via an IP44 terminal box, which is supplied loosely. Single-phase motors are delivered with the capacitor fixed to the terminal box.

Sense of rotation
The direction of rotation ERS type fans is clockwise, viewed from the inlet side. For DRS type fans it is counter-clockwise, viewed from the cable outlet side.

Fan performance curves
The performance curves for these fan types have been established in mounting position B (installed on the pressure side and open on the suction side) and represent the static pressure increase Dpst as a function of the volume flow. The dynamic pressure pd2 refers to the flange cross-sectional area of the fan outlet.

Sound Levels
The sound figures given in the fan performance curves are the A-weighted sound power levels LWA6 at the outlet side, unducted, in


Standard motor drive

- centrifugal fans direct drive
TN/HN direct-driven fans are single-inlet fans for light industrial applications.  They're used to convey clean or lightly polluted air and non-aggressive gases. TN model fans have forward-curved impellers,HN type fans are fitted with backward-curved impellers. The fan casings are not gas tight. The permissible temperature range of the conveyed medium is -30°C to +60°C.

The housing of the fans is made of galvanised sheet steel.  Painted or powder coated casings are available.
TNF. / HNF. - type fans are fitted with a B5 flange motor (fan sizes 160 - 280). The side plates and the scroll plate are joined together by a standing seam.  The mounting feet are screwed to the fan casing.  The discharge orientation can therefore easily be changed in steps of 90°.
TNQ. / HNQ. - type fans feature a square side plate (fan sizes 200 - 630) that allow the installation of a B3 foot motor.  The side plates and scroll are riveted.
The designation of discharge orientation and direction of rotation correspond to the Eurovent guideline from 1975.  The direction of rotation is seen from the drive side.  When ordering, please indicate the exact discharge position.

TN - Forward-curved impellers are made of galvanised steel, designed for high circumferential speed.  The inlet cones are manufactured from galvanised steel or glass fibre reinforced polyamide.
HN - Backward-curved impellers are made of seawater proof aluminium.  Their low mass moment of inertia allows to reduce motor sizes.  The inlet cones are made of galvanised steel.
All fan impellers are statically and dynamically balanced in two plains to quality level G 2.5 (DIN ISO 1940).

All fans are equipped with standard IEC-motors of flange or foot type.  Protection class IP55 isolation class F. The permissible ambient temperature range is -20°C to +40°C.  Up to motor size 100, voltagecontrollable motors are available.

Speed Control
Electronic and transformer-type speed controllers are available.  For controller details, please refer to chapter 7 of the catalogue.

Fan performance curves
The performance curves for these fan types have been established in mounting position B (installed on the pressure side with free inlet) and represent the total pressure increase as a function of the volume flow. The dynamic pressure refers to the flange cross-sectional area of the fan outlet.

Sound levels
The ascertaining of the sound data follows the enveloping surface method according to DIN 45 635 section 38, or the channel technique as defined in DIN 45 635, section 9.
It is important to note that reflexion and environmental characteristics as well as resonant frequencies influence the sound pressure levels in different ways.

Chemical resistant
Design features of the
Chemical-resistant Centrifugal Fans

The CHEM series of fans is characterised by high-efficiency impellers,reliable, maintenance-free operation as well as excellent corrosionresistance.  With the CHEM range, Wolter offers a complete series of high-quality backward-curved centrifugal fans with superior performance and low noise emissions.  Different materials can be processed in order to meet the demands of a multitude of applications in the chemical industry and to convey different types of process air or gases.  All fans are tested and rated in accordance with DIN 24163 and ISO 5801.

The fan casing is either made from thermoplastics such as PP, PVC,PE, PVDF or glass-reinforced polyvinyl-ester material (GRP or FRP). The fan casing is formed as a true spiral and has a high-efficiency inlet cone to ensure an even distribution of air over the full width of the impeller.
The models CHEM 125 - 250 are completely made of injection-moulded plastic and can be operated in either LG or RD rotational sense.  The plastic injection-moulded backplate or inlet cover can easily be removed in order to change the direction of rotation or for maintenance purposes. Fan casings with outlet flange are fitted with a chemical-resisant seal to prevent air leakage.  The standard casing material is PP.
The casings of types CHEM 315 to 400 are either made of GRP material or vacuum-formed and machine-welded. T he plastic injection-mould backplate can easily be removed for maintenance and service purposes. Thermoplastic fan casings with outlet flange are fitted with a chemicalresistant seal to prevent air leakage.  The GRP fan casing has a round outlet. Suitable flexible connectors are available.

Centrifugal backward-curved impeller
Wolter CHEM range fan impellers are designed as single-inlet, single-width (SISW) type. Impellers are made of precision plastic injection-mould parts with cast-in steel hub, which are subsequently mechanically welded. Standard impeller material is PP. Depending on the type of application, different materials such as PA, PC, PVC or PVDF can be processed.  If the application calls for high temperature resistance, flame-retardant properties,UV durability or protection against electrostatic discharge, special reinforced compound materials can be used. Each impeller is statically and dynamically balanced in two planes in accordance with Q2.5 of VDI 2060. The impellers are designed for use with taper-bushes and are made of high-grade cast disks guaranteeing solidity at high peripheral speed.  For a description of models... CHEM 75 and CHEM 90, please refer to ourindividual catalogue R05.

Fan base and support
The supporting steel stands and fan bases are manufactured from heavy gauge mild steel and are hot-dip galvanised or powder coated to provide protection even in the most adverse conditions. Special surface treatments can be applied on request.  Fans can be mounted in different discharge positions.

Drive shaft and bearing
All shafts comply to DIN 17210 - C45, they are trued and have a smooth finish.  Both shaft ends comply with DIN 748, Sheet 1 and are grooved in accordance with DIN 6885, Sheet 1.  A protective coating is applied on the shaft in order to prevent corrosion.  If needed, stainless steel shafts can be provided.
CHEM 125 to CHEM 400 belt-driven fans are fitted with cast aluminium flanged grooved ball bearings with an acid-proof seal, ensuring minimum vibration.

Precisely balanced pulleys with tension sleeve are used. All belts comply with ISO 4148. The belt-drive and all other rotating parts are fitted with a protection guard.

If the application requires, motors of different protection classes can be supplied.  On direct-driven fans, B5 flange-type motors are mounted.  All motors are totally enclosed and air-cooled.  Single-phase motors or motors with non-standard voltages can be supplied upon request

Standard colours
  All PP fans - PANTONE Warm Grey 1C 
  All GRP fans - PANTONE 430 
  If required, other colours can be supplied.

Ancillary equipment

  • Spring anti-vibration mounts

  • Condensate drain plug

  • Fan and motor support base frame

  • Shaft and bearing cover

  • Inlet flanges, flexible connections with clamps

  • Splinter shield


  • variational colouring

  • flame-retardant and temperature-resistant material

  • Anti-static material

  • UV-proof material

Permissible temperature range 
The temperature of the conveyed gases must not exceed the following limits: