Finder 7F.21.9.024.4250 – 7F Series Filter Fans – Reverse flow

Why Choose the Finder 7F.21.9.024.4250 Reverse Flow Filter Fan?

The Finder 7F.21.9.024.4250 is a high-performance 24 V DC reverse flow filter fan designed to extract warm air from industrial electrical cabinets, automation control panels and machinery enclosures. Part of the Finder 7F Series, this Size 4 enclosure ventilation fan delivers a nominal 250 m³/h free-air airflow, helping maintain suitable operating temperatures for sensitive electrical and electronic equipment.

Unlike conventional intake filter fans, the Finder 7F.21 reverse flow configuration is designed to exhaust air from inside the electrical cabinet to the surrounding environment. This makes it particularly useful for electrical enclosure cooling systems where warm air must be actively removed through a powered exhaust outlet, with replacement air entering through a suitably positioned filtered opening.

Operating from a 24 V DC supply, the Finder 7F.21.9.024.4250 features a 43 W rated power consumption, a robust 255 × 255 mm Size 4 housing, a replaceable filter mat and IP54 / NEMA Type 12 protection when correctly installed. Its snap-in mounting arrangement, push-in electrical connections and RAL 7035 grey finish make it a practical choice for industrial control panel manufacturers, electrical engineers and maintenance professionals.

Key Advantages

• 24 V DC operation for integration into compatible low-voltage industrial control systems.
• 250 m³/h nominal free-air airflow provides effective ventilation for electrical enclosures.
• Reverse flow exhaust configuration removes warm air from inside industrial cabinets.
• Approximately 195 m³/h airflow with a corresponding exhaust filter provides a useful indication of installed ventilation performance.
• 43 W rated power consumption supports the high-airflow DC fan assembly.
• IP54 protection rating helps maintain enclosure protection when the fan is correctly installed.
• NEMA Type 12 protection classification supports suitable indoor industrial installations.
• Size 4 construction provides a standardised mounting format for larger electrical cabinets.
• Snap-in mounting system helps reduce installation time.
• Push-in electrical terminals simplify connection to the DC supply.
• Replaceable G3 filter mat supports routine maintenance and filtration performance.
• RAL 7035 grey housing complements standard industrial electrical enclosures.
• Approximately 50,000-hour service life at 40 °C under specified operating conditions.
• 64 dB(A) nominal noise level provides a defined acoustic characteristic for enclosure design.
• Compatible Size 4 accessories simplify selection of replacement filter media and complementary ventilation components.
• Suitable for industrial automation, electrical distribution and machinery control applications.

Key Features

• Finder 7F Series industrial enclosure ventilation fan.
• Type 7F.21 reverse flow filter fan.
• 24 V DC nominal supply voltage.
• 19.2–26.4 V DC operating voltage range.
• 250 m³/h nominal free-air volume.
• 195 m³/h nominal airflow with a corresponding exhaust filter installed.
• 43 W rated power.
• 1.8 A nominal current consumption.
• Reverse flow / exhaust airflow direction.
• Size 4 fan and filter grille assembly.
• 255 × 255 mm front dimensions.
• 104.2 mm overall depth.
• 223 × 223 mm nominal mounting cut-out.
• IP54 protection rating.
• NEMA Type 12 enclosure protection classification.
• RAL 7035 grey housing.
• G3 filter mat according to EN 779.
• 80–90% nominal filtration degree under the manufacturer's specified test conditions.
• Self-extinguishing synthetic fibre filter material.
• UL94 V-0 plastic housing and cover.
• Snap-in panel mounting.
• Push-in electrical connections.
• 64 dB(A) noise level.
• 50,000-hour nominal service life at 40 °C.
• Operating ambient temperature range of −15 to +55 °C.

Reverse Flow Exhaust Ventilation for Industrial Electrical Cabinets

The Finder 7F.21.9.024.4250 is specifically designed to improve thermal management in electrical enclosures by actively extracting heated air. Industrial electrical equipment such as variable frequency drives, power supplies, transformers, contactors and automation controllers generates heat during operation. Without adequate ventilation, this heat can accumulate inside the cabinet and increase the temperature of sensitive components.

The reverse flow design moves air from inside the enclosure towards the surrounding environment. This is an important distinction from standard intake filter fans, which draw ambient air into the cabinet. The Finder 7F.21.9.024.4250 is therefore particularly suitable for applications where the enclosure cooling design requires a powered exhaust fan.

With a 250 m³/h nominal free-air airflow, this Size 4 fan provides substantial ventilation capacity for medium and large industrial electrical enclosures. The free-air rating describes the fan's performance under specified low-resistance conditions and should not be treated as the guaranteed airflow through a complete cabinet.

When used with a corresponding exhaust filter in the ventilation arrangement, the specified airflow is approximately 195 m³/h. This reduction illustrates the effect that filters and airflow resistance can have on installed ventilation performance.

For effective cooling, the exhaust fan should be paired with a suitable make-up air inlet. The inlet should be positioned to encourage air circulation through the cabinet, ideally across heat-generating components, rather than allowing incoming air to travel directly to the exhaust opening without cooling the equipment.

24 V DC Operation for Industrial Automation Systems

The Finder 7F.21.9.024.4250 operates from a nominal 24 V DC supply, making it suitable for industrial control panels that already use 24 V DC power distribution for automation equipment.

Its specified operating voltage range is 19.2–26.4 V DC, equivalent to 80–110% of the nominal supply voltage. The power supply must be capable of delivering the required operating current while maintaining the voltage within this range.

With a 1.8 A nominal current consumption and 43 W rated power, the fan should be included in the control panel's DC power budget. Installers should also consider any starting characteristics and protective device requirements stated in the manufacturer's installation instructions.

The DC supply arrangement is particularly useful for machine builders and automation engineers who want to integrate enclosure ventilation into an existing low-voltage control system. Where automatic fan operation is required, a suitably rated thermostat, controller or switching device may be used to control the supply.

This model is a DC-powered fan. It must not be connected directly to a 120 V AC or 230 V AC supply. For installations using AC power, a corresponding Finder 7F Series AC filter fan should be selected instead.

Replaceable G3 Filter Mat and Reliable Enclosure Protection

The Finder 7F.21.9.024.4250 includes a G3 filter mat according to EN 779, designed to help manage airborne dust and particles within the ventilation path. The filter uses progressive synthetic fibre material with a specified filtration degree of approximately 80–90% under the manufacturer's test conditions.

The filter material is temperature-resistant up to +100 °C and is classified as self-extinguishing according to Class F1 of DIN 53438. The fan housing and cover are manufactured from plastics conforming to UL94 V-0.

As dust accumulates in the filter mat, airflow resistance increases and ventilation performance can decrease. Regular filter inspection and replacement are therefore important for maintaining the cooling effectiveness of the electrical enclosure.

The corresponding replacement filter mat for this Size 4 assembly is the Finder 07F.45. Using the correct replacement filter helps maintain the intended fit, filtration characteristics and enclosure protection.

The fan provides an IP54 protection rating when correctly installed. It is also associated with a NEMA Type 12 enclosure protection classification for suitable indoor industrial installations. These ratings depend on correct mounting, suitable enclosure construction and proper maintenance of the filter and grille assembly.

Size 4 Snap-In Mounting and Easy Electrical Connection

The Finder 7F.21.9.024.4250 uses a Size 4 housing with overall dimensions of approximately 255 × 255 × 104.2 mm. It is designed for installation into a nominal 223 × 223 mm enclosure cut-out.

The snap-in mounting arrangement helps simplify installation into a correctly prepared panel opening. Before cutting or modifying the enclosure, the installer should check Finder's dimensional drawing for the exact cut-out tolerances, permitted panel thickness and installation requirements.

The fan features push-in electrical terminals suitable for conductor sizes from 0.7 to 2.5 mm² (AWG 18–14). These connections support efficient wiring during electrical cabinet manufacture and maintenance.

The RAL 7035 grey housing complements standard industrial enclosure finishes, providing a consistent appearance when installed in electrical distribution boards, machine control cabinets and automation panels.

The specified operating ambient temperature range is −15 to +55 °C. The fan should be installed where the surrounding conditions remain within the manufacturer's limits and where the enclosure ventilation system can provide adequate cooling.

Industrial Thermal Management and Equipment Reliability

Effective enclosure ventilation helps reduce the risk of excessive internal temperatures, which can shorten the service life of electrical and electronic components. The Finder 7F.21.9.024.4250 supports this objective by promoting forced-air exchange between the enclosure and its surrounding environment.

However, a filter fan cannot cool an electrical cabinet below the temperature of the incoming ambient air. If the ambient temperature is too high, or if the enclosure must remain sealed against aggressive contaminants, an enclosure air conditioner or another cooling method may be more appropriate.

Fan selection should account for the total heat generated by the equipment, the maximum permitted internal temperature, the surrounding ambient temperature and the resistance created by filters and cabinet construction.

Its 50,000-hour nominal service life at 40 °C provides a useful reference for maintenance planning, although actual service life will depend on operating conditions, ambient temperature and environmental exposure.

Typical Applications

• Industrial electrical cabinet exhaust ventilation.
• 24 V DC automation control panel cooling.
• PLC and industrial control system enclosures.
• Variable frequency drive and motor control cabinets.
• Electrical distribution and switchboard ventilation.
• Industrial machinery electrical panels.
• Manufacturing and production line automation cabinets.
• Power supply and transformer enclosure cooling.
• Packaging and processing machinery.
• Machine tool electrical enclosures.
• Industrial process control cabinets.
• OEM electrical cabinet manufacturing.
• Electrical enclosure refurbishment and maintenance.
• Low-voltage DC cabinet ventilation systems.
• Applications requiring reverse flow exhaust rather than standard intake ventilation.