A forced draft fan pushes fresh air or preheated combustion air into a furnace, boiler, burner or kiln.
An induced draft fan pulls hot flue gas through heat exchange, dust control equipment and the chimney.
In many boiler systems, FD and ID fans work together to maintain stable combustion and furnace draft.
Final selection still depends on airflow, pressure, temperature, dust load, material, fan speed and installation direction.
Fan Position Decides the Duty
In boiler and furnace systems, the terms forced draft fan and induced draft fan describe where the fan works in the draft route. The FD fan is on the air-supply side, usually before the furnace. The ID fan is on the flue-gas exhaust side, usually after the boiler, dust collector or other gas cleaning equipment.
This difference affects the medium temperature, dust loading, corrosion risk, bearing arrangement, material selection, impeller design, motor position and maintenance requirement.
Main Differences Buyers Should Confirm
FD fans and ID fans may both be centrifugal fans, but their working conditions are different. The comparison below helps avoid choosing only by model number or motor power.
| Item | Forced Draft Fan | Induced Draft Fan |
|---|---|---|
| System side | Air-supply side before furnace | Flue-gas exhaust side after boiler or collector |
| Airflow direction | Pushes air into the combustion zone | Pulls flue gas out of the system |
| Typical medium | Clean air or preheated combustion air | Hot flue gas, dust, ash, moisture or corrosive gas |
| Pressure review | Burner, damper, air-preheater and duct resistance | Boiler, dust collector, scrubber, duct and chimney resistance |
| Selection risk | Combustion air shortage or unstable burner operation | High temperature, dust wear, corrosion and insufficient draft |
| Common use | Boiler forced draft, furnace air supply, burner support | Boiler induced draft, flue gas exhaust, dust-removal system |
How FD Fan and ID Fan Work Together
In a balanced draft boiler system, the FD fan provides enough combustion air while the ID fan removes flue gas and keeps the furnace draft stable.
What to Confirm Before Selecting FD or ID Fan
For Forced Draft Fan
For Induced Draft Fan
Continue Fan Selection from QIYUE FAN Pages
Use these pages to move from concept comparison to product direction, boiler draft fan selection and RFQ preparation.
What Data Should Be Sent for Fan Selection?
To select a forced draft fan or induced draft fan accurately, QIYUE FAN recommends confirming the following information before quotation.
Related Industrial Fan Selection Guides
FAQ About Forced Draft and Induced Draft Fans
Is a forced draft fan the same as an induced draft fan?
No. A forced draft fan supplies air into the furnace or boiler system. An induced draft fan extracts flue gas after combustion and usually works on the exhaust side.
Which fan needs more attention to temperature and dust?
The induced draft fan usually needs more attention to temperature, dust, ash, moisture and corrosion because it handles flue gas after combustion.
Can one centrifugal fan series be used for both FD and ID duties?
Some centrifugal fan series can be configured for different draft positions, but the final choice depends on airflow, pressure, gas temperature, dust condition, material, speed, drive type and installation direction.
Should I select the fan by motor power first?
No. Motor power is checked after airflow, pressure, speed, efficiency and working point are reviewed. Choosing only by motor power can lead to insufficient airflow or unnecessary energy consumption.
What pressure losses should be included for an ID fan?
ID fan selection should include boiler or furnace resistance, dust collector resistance, scrubber resistance, duct loss, elbow loss, damper loss and chimney discharge loss.
What information should I send before quotation?
Please send application, airflow, static pressure or total pressure, gas temperature, medium condition, dust load, fan position, motor voltage, frequency, rotation, outlet angle, drive arrangement and quantity.
Send Your Boiler or Furnace Draft Fan Parameters
QIYUE FAN can review airflow, pressure, gas condition, temperature, fan position, motor standard, outlet angle and drive arrangement before recommending a suitable forced draft fan or induced draft fan direction.