Centrifugal in line - BT3 250

Casals BT3 250 Inline Centrifugal Fan – Reliability and Efficiency in Ductwork

The BT3 250 inline centrifugal fan by Casals is the professional solution for discreet and efficient integration into Ø250 mm circular duct ventilation systems. With a single-phase asynchronous external rotor motor, galvanised steel casing and backward-curved blade impeller, this fan delivers an excellent balance of airflow, energy efficiency and durability at standard 230 V / 50 Hz supply voltage.

Robust construction for long service life

The galvanised steel casing provides superior corrosion resistance, making it suitable even for humid environments. The dynamically balanced backward-curved blade impeller minimises vibrations and operating noise while delivering optimised airflow and high aerodynamic efficiency. The electrical connection box is positioned outside the airstream, simplifying installation and protecting connections from moisture, dust and heat.

External rotor motor – performance and zero maintenance

The single-phase asynchronous external rotor motor rated at 152 W (0.152 kW) is supplied at 230 V / 50-60 Hz and features:

• Automatic thermal protection with auto-reset – protects the motor against overheating without manual intervention
• Lifetime-lubricated bearings (40,000 operating hours) – no lubrication or periodic maintenance required
• IP44 protection rating – resistance to solid particle and water splash ingress from any direction
• 2-pole motor – high-speed operation for optimal airflow

Fast and flexible installation

The BT3 250 is supplied with mounting brackets included, enabling quick fixing to false ceilings, walls or metal frameworks. It connects directly to Ø250 mm circular ductwork and integrates into both centralised ventilation systems and local installations. For sizes 200 to 315, fans can be fitted on request with a metal impeller for enhanced resistance in higher-temperature or more demanding applications.

Recommended applications

The BT3 250 is suitable for: general ventilation in apartments and houses, office and commercial space ventilation systems, HoReCa installations – restaurants, hotels, kitchens with moderate extraction, classrooms and educational facilities, false ceiling ventilation with limited void depth, replacement of existing fans in Ø250 mm duct installations.

Important note: Maximum air temperature for continuous operation is 50°C. This fan is not approved for conveying explosive or flammable gases.

Key advantages:

• External rotor motor with lifetime bearings (40,000 h) – zero maintenance
• Galvanised steel housing – corrosion and humidity resistant
• Automatic thermal protection – safe operation without intervention
• Dynamically balanced backward-curved impeller – reduced vibration and noise
• Connection box outside the airstream – simplified installation and servicing
• IP44 – suitable for humid and semi-humid environments
• Mounting brackets included – quick installation
• Metal impeller option on request (sizes 200–315)

TECHNICAL SPECIFICATIONS TABLE:

FAQ – FREQUENTLY ASKED QUESTIONS:

Q: What is an inline centrifugal fan and how does it differ from an axial fan? A: An inline centrifugal fan mounts directly in the ductwork with air entering and leaving on the same axis, but uses a centrifugal impeller internally. Compared to axial duct fans, centrifugal fans generate higher static pressures, making them suitable for longer duct runs, multiple bends or installations with significant hydraulic resistance. The BT3 250 is the right choice when a simple axial fan can no longer deliver the required airflow against the system resistance.

Q: What does "external rotor motor" mean and what are the advantages? A: An external rotor motor has the rotor mounted on the outside of the stator, directly on the fan impeller or casing. This design provides a larger cooling surface, better inertia characteristics and a more compact motor-impeller integration. The result is higher efficiency, lower noise levels and a longer service life compared to conventional internal rotor motors at the same power rating.

Q: How long do the bearings last and what maintenance does the fan require? A: The bearings are lifetime-lubricated for 40,000 operating hours, equivalent to approximately 16 years of continuous operation or considerably longer in typical intermittent use. No lubrication or bearing replacement is required. The only recommended maintenance is occasional cleaning of the impeller and casing to remove dust deposits and maintain aerodynamic performance.

Q: What happens if the motor overheats? A: The motor is fitted with automatic thermal protection with auto-reset. If the motor temperature exceeds the rated limit – for example due to mechanical blockage, incorrect voltage or excessive ambient temperature – the thermal protection shuts the motor down automatically. It restarts on its own once cooled, without any manual intervention.

Q: What duct diameter does the BT3 250 fit and are reducers available? A: The BT3 250 is designed for Ø250 mm circular ductwork. If the existing installation uses a different diameter, reducers for Ø250 mm (from Ø315, Ø300 or down to Ø200, Ø100), anti-vibration flexible connectors Ø250 and 45°/90° elbows are available as related products on the product page for duct adaptation.

Q: Can the BT3 250 be used with a speed controller? A: Yes. The single-phase asynchronous motor is compatible with TRIAC-type electronic speed controllers (with capacitor). Compatible speed controllers are available as accessories on the product page, both with and without display, allowing airflow and energy consumption to be reduced according to requirements.

Q: Is it suitable for installation in a false ceiling? A: Yes. The BT3 250 can be installed in a false ceiling thanks to its compact design and included mounting brackets. It is recommended to ensure maintenance access and to fit an anti-vibration flexible connector on at least one duct connection to reduce vibration transmission to the building structure.

Q: How can I order or request technical advice? A: You can order directly through the product page form, or contact us at +40 722 667 239 (phone/WhatsApp) for free technical advice on selecting the right fan and accessories for your installation.