Duct Path First
A short straight run and a filtered cabinet path are different projects even if both use the same duct diameter. The fan must overcome the installed resistance, not just fit the opening.
Capture straight length, elbow count, transitions, grilles, filters, dampers, and termination. If the path is unknown, the review is not ready for final product comparison.
Inline Fan Limits
MiWind Ventilation Fans cover simpler inline paths as well as cabinet-style reviews when pressure, filtration, access, or serviceability becomes more important. Exhaust Fans remain relevant when the source is a room exhaust condition.
Booster fan requests should be handled carefully. A weak branch or existing system complaint needs details about the existing fan, duct route, controls, and sound expectations.
Service access and controls are part of the selection
A fan buried above a ceiling, behind a filter, or inside a service area has a different maintenance profile. Access constraints should be discussed before the equipment family is narrowed.
Speed control, sensors, timers, switches, and continuous operation also shape the selection. They affect electrical discussion, operating expectation, and document details.
Recognize pressure clues
Filters loaded with dust, undersized grilles, multiple elbows, flex duct, dampers, backdraft devices, and tight termination caps are all clues that diameter alone will understate the fan work. These clues should be written down before asking for a fan family.
When the duct path includes filtration or a cabinet, the review may move away from a simple inline fan toward a cabinet, utility, or pressure-focused product discussion.
Define the system boundary
For booster work, identify the existing fan, weak branch, room source, control method, and complaint. Adding a fan into an unknown system can create noise, imbalance, or maintenance issues if the original boundary is unclear.
For new work, state whether the fan is serving outdoor air, transfer air, exhaust, filtration, or process airflow. That single sentence often prevents the wrong equipment family from entering the conversation.
Prepare for fan-curve review
Equivalent length is only a screening note. A real duct fan review still needs the target CFM, estimated pressure path, voltage, controls, sound expectation, and any filtration or grille restriction.
When those details are available, the distributor can compare product data and fan curves instead of guessing from duct diameter or cabinet size.
Resistance note
The short check turns straight duct length and elbows into a simple equivalent-length note. It is a guide-level estimate; final fit still needs model fan curves.
Enter CFM, straight duct length, and elbows to create a quick resistance note.
diameter fails
A fan that matches the duct diameter can still miss the airflow target if filters, grilles, elbows, or termination are ignored. The final review should combine CFM, pressure path, sound, voltage, controls, and model data.
Duct Fan Matrix
The matrix maps installed conditions to the first fan family to review.
| Installed condition | Project facts | Related page | MiWind family |
|---|---|---|---|
| Simple inline run | CFM, duct size, length, termination, controls | Ventilation CFM Calculator | Ventilation Fan |
| Filtered or access cabinet | CFM, filter path, pressure, service clearance | Static Pressure Estimator | Cabinet centrifugal fan |
| Inline cabinet fan request | CFM, static pressure estimate, access side, equipment-room space | Static Pressure Estimator | Cabinet centrifugal fan |
| Booster support | Existing fan context, weak branch, duct route, sound | Ventilation CFM Calculator | Booster or inline selection |
| Exhaust path | Source, CFM, duct route, noise target, controls | Bathroom or Ventilation CFM Calculator | Exhaust Fans plus Inline Fans |
| Inline duct-size request | 4/6/8/10/12 inch inline options, duct length, elbows, termination | Duct Fan Static Pressure Estimator | Inline Duct Fan |
| EC control request | 4/6/8 inch EC inline options, speed, temperature or humidity control | Duct Fan Static Pressure Estimator | EC Inline Duct Fan |
| Filtered duct run | Carbon or HEPA filter pack, pressure impact, service access | Duct Fan Static Pressure Estimator | HEPA Purified Duct Fan |
| Wall exhaust path | 6/8/10/12 inch opening, shutter behavior, wiring, termination | Bathroom or Ventilation CFM Calculator | Wall Mounted Exhaust Fans |
Source-backed fan data to keep with the duct path
Use source airflow, pressure, and duct-size references for screening only; final fan curves and model documents decide project use.
| Fan path | Published source reference | Pressure or access note | Selection use |
|---|---|---|---|
| Inline Duct Fan | Source air volume range 120-1900 m3/h with 4/6/8/10/12 inch duct options | Fan curve needed for the selected pressure point | Use for mixed-flow duct runs after CFM, length, elbows, and termination are known |
| EC Inline Duct Fan | Source air volume range 240-540 m3/h with 4/6/8 inch EC inline options | Confirm speed, temperature, and humidity control package | Use where variable occupancy airflow or sensor response matters |
| Booster Fan | Source air volume range 240-540 m3/h | Source static pressure range 142-295 Pa | Use only after the weak-airflow branch and pressure-loss reason are known |
| HEPA Purified Duct Fan | Source air volume range 160-920 m3/h | Carbon or HEPA filter pack adds pressure impact and service-access requirements | Keep filter service and pressure impact with the fan selection |
| Cabinet Centrifugal Fan | Source range is 2000-25000 CMH; convert and confirm exact CFM | Source static pressure range 400-740 Pa | Use for higher-pressure or service-access cabinet paths |