SISW and DIDW centrifugal fans: single-inlet vs double-inlet
SISW — single inlet, single width — pulls air through one side and suits compact, ducted duties; DIDW — double inlet, double width — pulls through both sides of one wheel, so it delivers roughly twice the airflow in a wider but shallower envelope and at lower tip speed.
The acronyms come from fan geometry, not from a product family. SISW means one inlet and one impeller width; DIDW means the same wheel is fed from both sides and therefore twice the impeller width is available to move air. Both are centrifugal fans: they trade volume for pressure, which is why they appear in air handling units, kitchen extractors, dryers and cleanrooms where axial fans cannot hold the duty point. This page collects the models we build in each arrangement so the airflow, pressure and mounting size can be compared directly.
Selection points
- Start with airflow and pressure, then let the arrangement follow: DIDW gives about double the airflow of a SISW wheel at the same diameter and speed.
- DIDW housings are wider front-to-back but shorter in diameter, which matters when the AHU panel height is fixed.
- SISW is the right choice for ducted runs with a single inlet path and for units where the motor sits behind the impeller.
- Do not compare a clean SISW curve with a DIDW curve measured at a different speed — normalise to the duty point first.
Model comparison
| Model | Airflow | Max static pressure | Power | Noise | Voltage |
|---|---|---|---|---|---|
| BC310A-E092E3-02 | 2500 m³/h | 715 Pa | 240 W | 74 dB(A) | 230 V AC |
| BC310B-E092E3-01 | 2500 m³/h | 615 Pa | 175 W | 71 dB(A) | 230 V AC |
| BC310A-E092D3-01 | 2100 m³/h | 715 Pa | 160 W | 64 dB(A) | 230 V AC |
| BC280B-E092E3-02 | 2000 m³/h | 460 Pa | 200 W | 65 dB(A) | 230 V AC |
| BC310A-E092D1-01 | 1950 m³/h | 715 Pa | 160 W | 64 dB(A) | 115 V AC |
| BC250A-A092D3-01 | 1400/1800 m³/h | 615 Pa | 175/230 W | 74 dB(A) | 230 V AC 50/60Hz |
| BC280A-E092E1-02 | 1800 m³/h | 715 Pa | 220 W | 77 dB(A) | 115 V AC |
| BC280A-E092E3-02 | 1800 m³/h | 715 Pa | 200 W | 77 dB(A) | 230 V AC |
| BC310B-E092E1-01 | 1750 m³/h | 615 Pa | 175 W | 71 dB(A) | 115 V AC |
| SF160D-E092B3-02 | 1700 m³/h | 705 Pa | 180 W | 62±2 dB(A) | 230 V AC |
| SF160D-E092B3-42 | 1690 m³/h | 705 Pa | 240 W | 60±2 dB(A) | 230 V AC |
| BC250A-E092E3-03 | 1680 m³/h | 750 Pa | 240 W | 77 dB(A) | 230 V AC |
Specs are taken from each model's product page — full curves, dimension drawings and certificates live on the model pages. Models not listed can be browsed by series in the product catalogue.
Frequently asked questions
What does SISW stand for in fans?
Single Inlet Single Width: the impeller has one inlet side and one width of blading, so air enters from one side only. It is the compact arrangement used in ducted centrifugal fans and single-path AHUs.
What does DIDW stand for and when should I choose it?
Double Inlet Double Width: air enters both sides of a double-width impeller. Choose it when a given airflow must fit a smaller diameter and lower tip speed — air handling units, kitchen extractors and dryer duties with long duct runs.
Are DIDW fans more efficient than SISW fans?
Not as a rule. Efficiency depends on the impeller profile and how close the duty point sits to the best-efficiency point. DIDW mainly buys airflow per unit of diameter; a well-matched SISW wheel can post the same or better efficiency in a narrow duty range.
Can these fans run on EC motors?
Yes — both arrangements are built with EC external-rotor motors, with 0-10 V, PWM or Modbus control, so speed can follow the load instead of being throttled by a damper.