English
Le français
Türkçe
The motor of a smoke extract fan is the electric motor that turns the impeller of the fan that pushes hot smoke out of a building during a fire; but in this duty the motor is part of a set tested together with the fan and certified to EN 12101-3, and it cannot be chosen or replaced on its own. If the motor of a fan that must work in smoke mode fails, only the fan manufacturer's certified spare motor or a motor it approves may be fitted. DRG's standard three-phase motors are not sold with this certification; a DRG motor can only be recommended for fans that have no smoke duty and provide normal ventilation.
This page covers fan types, EN 12101-3 classes, the power range and the boundary between normal and smoke mode. For fans without a smoke duty you can find suitable motors on the Buy Electric Motors Online page. Overview: Fan Motors.
What is a smoke extract fan, and which fan types are used?
"Smoke extraction" is not the name of an operating principle or a housing type; it is a purpose. Fans of different principles and housings serve the same purpose; what they share is test evidence that they keep running at a given temperature for a given time. Four types are common on site:
- Axial duct (long-cased) fan: flanged to a duct or wall opening, it moves large flows at low to medium pressure. One manufacturer's range has impeller diameters of 350–1400 mm [1].
- Centrifugal roof fan: sits on the roof and discharges smoke vertically. It uses a backward-curved impeller; the motor is inside the set and its cooling air comes through a separate duct [2].
- Belt-driven centrifugal box fan: a volute impeller inside an insulated box, with a foot-mounted motor outside connected by pulleys and V-belts [3]. It handles higher pressure and is used on long duct runs.
- Axial jet fan: pushes smoke in one direction without ducts in car parks and tunnels. The motors of these fans are covered separately on our car park jet fan and tunnel jet fan pages; we do not repeat them here.
Places of use: shopping centre and warehouse roofs, atriums, stairwell and corridor exhaust shafts, industrial production halls, ducted exhaust lines of enclosed car parks. Most of these fans are "dual purpose": they ventilate every day and switch to smoke mode when the fire signal arrives [1].
Where does the motor sit in the fan, and what does it do?
The motor's job is the same in every fan: to turn the impeller at the speed the fan curve requires. The difference lies in how the motor relates to the hot gas, and that depends on the fan type.
- In a direct-drive axial fan the impeller is on the motor shaft and the motor sits in the middle of the casing, right in the gas stream. Because it must keep running in 300–400 °C gas in smoke mode, the motor is a special high-temperature motor.
- In a roof fan the motor is above the impeller, close to the gas stream but in a separate compartment; one manufacturer uses a cooling duct that brings fresh air from outside into this compartment [2].
- In a belt-driven box fan the motor is outside the box, outside the gas path [3]. It is not directly exposed to hot gas; heat reaches it through the shaft, bearings and box wall. Even so, the certificate is issued to the set tested together with fan, belt drive and motor.
A motor outside the gas stream does not mean a standard motor can be fitted; even in a belt-driven fan the motor is part of the set.
EN 12101-3 classes: what do temperature and time mean?
EN 12101-3 covers powered fans used in smoke and heat control systems. A fan's class gives the gas temperature it was tested at together with the time it kept running at that temperature. The main classes in the standard's classification table are [4]:
| Class | Temperature | Time |
|---|---|---|
| F200 | 200 °C | 120 min |
| F300 | 300 °C | 60 min |
| F400 | 400 °C | 120 min or 90 min |
| F600 | 600 °C | 60 min |
Which class is needed is decided by the building's fire scenario and the smoke control design, not by the fan or motor supplier. A fan rated "F400" shows that fan, motor, bearings, cable connection and casing were tested together running at 400 °C for 120 minutes; it is not enough for only the motor or only the impeller to withstand that temperature.
Normal ventilation versus smoke mode: why a standard motor cannot be substituted
A dual-purpose fan works in two different regimes. In normal mode the air is at ambient temperature; one manufacturer limits air temperature to 55 °C in this mode for its roof fan [2]. The motor works in familiar conditions, its speed can be reduced by an inverter and thermal protection is active. In smoke mode the rules change:
- The fan must keep running at full power. One manufacturer requires that in a fire speed control, the inverter and the motor protection devices are bridged and the motor is connected directly to the mains [2]. The motor does not stop to protect itself; it runs until it fails.
- The motor's winding insulation, bearings and grease are chosen for high temperature. One motor manufacturer requires that only the grease and bearing types given on the plate are used for the certificate to remain valid [5].
- These motors may not be rewound; a motor that has been exposed to high temperature can no longer perform its safety function and must be replaced with a motor of the same features [5].
These three points explain why fitting a standard motor to a smoke extract fan is not acceptable: in a fire the standard motor fails at its own temperature limit, the set's certificate becomes invalid and responsibility passes to whoever made the change. DRG's standard motors have no smoke extraction certification; in these fans, motor replacement should be done through the fan manufacturer or its authorised service.
How many kW do smoke extract fan motors have?
A) Motor power seen in commercial fan models
| Model group / capacity | Motor power | Single / total | Source |
|---|---|---|---|
| Maker A, axial, 350 mm | 0.75–1.1 kW (2-pole) | Single motor | [1] |
| Maker A, axial, 1000 mm | 5.5–18.5 kW (4-pole) | Single motor | [1] |
| Maker A, axial, 1120 mm | 18.5–30 kW (4-pole) | Single motor | [1] |
| Maker B, roof fan, smallest | 0.55 kW | Single motor | [2] |
| Maker B, roof fan, largest | 28 kW | Single motor | [2] |
In this fan group, motor options of about 0.55–30 kW are seen depending on the manufacturer's model and capacity [1][2]. Each fan has a single motor; in two-speed fans, the two values belong to two speeds of the same motor. Even at the same diameter, blade angle and number of poles change the power: one manufacturer's 1000 mm axial fan has options of 5.5–18.5 kW at 4 poles and 1.5–5.5 kW at 6 poles [1]. Power is set by flow, pressure, impeller diameter and speed. Because hot gas has a low density, the power the fan absorbs at the same volume flow is lower in smoke mode; at 300 °C the gas density is about half that of air at 20 °C. What strains the motor in smoke mode is not the load but the temperature.
B) Motors with a match in the DRG range
In terms of power, the 0.55–30 kW range lies within DRG's 0.25–355 kW range; but this overlap only means something for normal ventilation mode. Motors of fans that must work in smoke mode are part of a certified set and are outside the DRG range. In addition, the 8-pole (750 rpm) and two-speed motors seen in some axial smoke fans are not in our store [1].
Worked example for normal mode and motor selection checklist
The motor of a fan with no smoke duty, used only for normal ventilation, is chosen as for other fans: P_shaft = Q·Δp / η_fan (Q m³/s, Δp Pa, P W). Example: an exhaust fan on a warehouse roof will move 36,000 m³/h (10 m³/s) at 350 Pa, only to remove hot air in summer. If fan efficiency is assumed to be 0.62, shaft power is 10 × 350 / 0.62 ≈ 5,650 W. With a 15% margin about 6.5 kW is needed and the standard power is 7.5 kW. If the fan is designed for a 4-pole motor, DRG-132M-4 (7.5 kW, 1460 rpm, 14.3 A at 400 V) fits. You can do the same calculation with your own values in the Pump & Fan Motor Power calculator.
Before asking for a motor for a fan that looks like a smoke extract fan, check the following:
- Does the fan label show "F200", "F300", "F400" or EN 12101-3? If so, the motor is obtained from the fan manufacturer, not from DRG.
- Is the fan defined in the building's fire scenario or on the smoke control panel? Check the design and operating documents.
- Old motor's nameplate: kW, rpm, frame, mounting type, insulation and temperature data, single or two speeds.
- Fan type: direct drive or belt drive; is the motor inside or outside the gas stream?
- Panel: direct-on-line, star-delta, inverter; is there a bypass circuit for the fire case?
- Maximum temperature and content (oil, moisture, dust) of the air in normal mode.
If the label shows no certification and the fan is not part of the fire scenario, it is an ordinary exhaust fan and its motor is chosen as for roof extract fans; see our article on the roof exhaust fan motor.
DRG motors: normal ventilation mode only
DRG Motor is a manufacturer, supplier and seller of electric motors. Our range covers 0.25–11 kW in aluminium frames and 0.55–355 kW in cast iron; 1000, 1500 and 3000 rpm; 3-phase, 230/400 V or 400/690 V; mounting B3, B5, B14 and B35 (with an order note). This range carries no smoke extraction certification. The models below are only for exhaust and roof fans with no smoke duty that provide normal ventilation:
| Model | Power / speed | Frame | Current 400 V |
|---|---|---|---|
| DRG-112M-4 | 4 kW / 1450 rpm | 112M cast iron | 7.95 A |
| DRG-132S-4 | 5.5 kW / 1460 rpm | 132S cast iron | 10.7 A |
| DRG-132M-4 | 7.5 kW / 1460 rpm | 132M cast iron | 14.3 A |
| DRG-160M-4 | 11 kW / 1465 rpm | 160M cast iron | 20.4 A |
| DRG-160L-4 | 15 kW / 1465 rpm | 160L cast iron | 27.3 A |
If unsure about the smoke duty, first send photos of the fan label and motor nameplate. Request a quote for the suitable motor and current price: contact page or WhatsApp. For a certified smoke extract fan we recommend directing the motor request to the fan manufacturer. DRG MOTOR motors are guaranteed against material and manufacturing defects for 2 years from the delivery date (warranty certificate).
Smoke extract fan motor: FAQ
Can a standard motor replace the burnt motor of a smoke extract fan?
Not if the fan has a smoke-mode duty. The certificate is issued to the set of fan and motor tested together; fitting a standard motor invalidates it. The fan manufacturer's certified spare motor should be used.
What is the difference between F300 and F400?
The class gives test temperature and time together: F300 means running at 300 °C for 60 minutes, F400 at 400 °C for 120 minutes (or 90 minutes). The fire and smoke control design decides which one is required.
Can a smoke extract fan run on an inverter?
In normal mode, often yes. In smoke mode the fan manufacturer's instructions apply; one manufacturer requires the inverter and motor protection to be bridged and the motor connected directly to the mains in a fire.
How many kW is a smoke extract fan motor?
It depends on the fan's flow, pressure and diameter. Commercial axial and roof smoke fans use motors of about 0.55–30 kW; the exact value comes from the fan label and the manufacturer's selection table.
Send us the fan label, the old motor's nameplate and the fan's duty in the building; if it is a normal ventilation fan, we will confirm the right DRG model together. Phone +90 (542) 666 11 11, e-mail [email protected], contact page, WhatsApp. All models for normal ventilation fans: Buy Electric Motors Online.
Sources
- Ferrari Fan Technology (UK) – Smoke Extract Fans, axial (katalog) – EN 12101-3 F300 and F400 (2 h) certified axial fans; 350–1400 mm impellers; dual purpose; single and two-speed motors; 0.55–30 kW motor combinations by size, 8-pole options.
- Systemair – Smoke extract roof fans DVV/F (data sheet) – F400/F600 roof smoke extract fan; IEC standard motor inside the set; shaft power 0.55–28 kW; air up to 55 °C in normal mode; in a fire, inverter and motor protection are bridged and the motor is connected directly to the mains.
- VIM – BSP F400 smoke extraction fan (ürün sayfası) – F400 120 certified belt-driven centrifugal box fan; 1,000–55,000 m³/h, 1,800 Pa; foot-mounted B3 motor, pulleys and V-belts.
- BS EN 12101-3:2015 – Smoke and heat control systems, Part 3: Powered smoke and heat control ventilators (fans) – Table F.8 classification: F200 200 °C/120 min, F300 300 °C/60 min, F400 400 °C/120 and 90 min, F600 600 °C/60 min, F842 30 min.
- ABB – Low voltage Smoke extraction motors, additional manual – smoke extraction motors built to EN 12101-3; rewinding not allowed; a motor exposed to high temperature is replaced with one of the same features; grease and bearing types specified for validity of certification.
