Fan control cabinets
- Starting method: direct-on-line, wye-delta reduced voltage, autotransformer reduced voltage, soft starter, VFD, two-speed pole changing (selected by power and airflow requirements)
- Two-speed control: high/low speed switching and time-delay protection for pole-changing two-speed fans, preventing direct reverse-connection switching
- Interlocking: sequenced start/stop interlocking with dampers, fire dampers, and upstream/downstream equipment, including damper position feedback confirmation
- Protection: overload, phase loss, short circuit, overheat, and locked rotor protection; differential pressure and filter differential pressure monitoring optional
- Multi-fan control: sequenced start/stop and rotation of multiple fans to avoid grid inrush from simultaneous starting
Specifications
The table below covers 80% of factory distribution room cases. Anything outside it we can still build — those are engineered items, quoted separately, with an indicative price the same day.
| Type | Floor-standing fan control cabinet / wall-mounted fan control box, single or multiple fans per cabinet |
|---|---|
| Standard sizes (W×D×H) | 600×600×1600 / 800×600×1800 / 1000×600×2000 mm, selected by power and fan count |
| Enclosure construction | 2.0 mm cold-rolled carbon steel, bent and welded with reinforcing ribs, electrostatic powder coated |
| Surface treatment | Degrease → derust → phosphating → electrostatic powder coating 60-80 μm, baked at 200 °C for 30 minutes |
| IP rating | IP54 standard / IP55 / IP65 optional (IP65 or a rain hood recommended for rooftop and outdoor installation) |
| Cooling | Top exhaust + bottom intake with filter; VFD options require separate heat calculation based on drive losses |
| Installation | Floor-standing or wall-mounted; leave ≥800 mm service access in front of the cabinet |
| Cable entry | Bottom cable entry with gland plate; for rooftop installation, point glands downward and seal them |
| Suitable power | 0.75–250 kW, starting method selected by power range |
|---|---|
| Starting method | Direct-on-line (≤7.5 kW), wye-delta reduced voltage (11–75 kW), autotransformer reduced voltage (37–160 kW), soft starter, VFD |
| Two-speed control | High / low speed switching for pole-changing two-speed fans, with switching delay and interlocking to prevent direct reverse-connection damage to the motor |
| Interlocking | Sequential start/stop and damper position feedback confirmation with air dampers, fire dampers, AHUs, and upstream/downstream process equipment |
| Multiple-fan control | Sequential start/stop and automatic rotation of multiple fans to prevent voltage sag from simultaneous starting |
| Protection | Overload, phase loss, short circuit, overheat, and locked rotor protection; optional air differential pressure switch and filter differential pressure alarm |
| Control interface | Local/remote selector switch; accepts start/stop and status inquiry signals from PLC or building automation (BA) |
| Signal output | Volt-free contacts for run, fault, and auto/manual status output to the control room |
| Single-fan star-delta starting | Conventional starting method for high-power fans; starting current reduced to approximately 1/3; simple and reliable design |
|---|---|
| Two-speed fan solution | Switches between high and low speed on demand; low speed for normal ventilation, high speed for emergency exhaust or process requirements |
| Variable frequency drive solution | Continuously adjusts air volume based on air pressure, temperature, or CO concentration signals; significant energy savings |
| Duty/standby fan configuration | Two fans in duty/standby operation; rotates based on running hours; automatic transfer on fault |
| Sequenced start/stop for multiple fans | Multiple fans start in sequence at set intervals and stop in reverse order to reduce impact on the power grid |
| Damper interlock solution | Confirms damper position before starting the fan; stops the fan before closing the damper on shutdown; includes damper position fault alarm |
| Reference standards | GB/T 7251.1 / IEC 61439-1 (assemblies); GB/T 5226.1 (electrical safety of machinery) |
|---|---|
| Clearance & creepage | Meets pollution degree 3 and overvoltage category III requirements |
| Insulation resistance | ≥1 MΩ (500V megohmmeter) |
| Power frequency withstand voltage | Main circuit 2500V / 1 min, control circuit 1500V / 1 min |
| Timing verification | Star-delta transition, two-speed switching, and sequential start/stop timing are tested and recorded before shipment to prevent switching surges |
| Routine tests (every unit) | Circuit checks, insulation and dielectric withstand tests, start/stop operation, interlock signal response, protection operation, and on-load trial run |
| Documents with shipment | Electrical schematic, terminal wiring table, timing description, BOM, test report, and factory photos |
Five steps to specify your run
A configuration summary is generated as you go. It travels with your inquiry, saving a round of confirmation.
Build details
Systems have been in service for decades, and the failure points are always the same few: poor busbar contact, water ingress at the door seal, high temperature rise in the correction cabinet, and mis-phased outgoing feeders. The six hard rules below are written for exactly these points — every cabinet can be traced to them.
Star-delta starting keeps the starting current down
Star-delta starting cuts the starting current to roughly 1/3 of the direct-on-line value, at the cost of an equally reduced starting torque. Fans are a variable-torque load, so this trade-off fits them well — but it does not carry over to heavy-duty equipment.
Allow a delay in the star-delta transition
Leave enough delay between the star and delta transition (set according to fan inertia). Switching too early causes a current surge from back EMF. This timing is measured and calibrated at the factory before shipment.
Sequence interlock
The start sequence is "open damper → confirm damper position → start fan," and the stop sequence is reversed. Starting the fan with the damper closed overloads it against a blocked pressure condition.
Two-speed changeover without hard switching
During two-speed fan changeover, the original speed circuit is disconnected first, and the other speed is only engaged after motor speed has dropped, avoiding the high current and mechanical shock of plugging.
Multiple fans do not start simultaneously
Multiple fans start in sequence at set intervals. Closing them all at once stacks the impact on the transformer, which is especially noticeable where supply capacity is limited.
Timing records delivered with the cabinet
The timing for star-delta transition, two-speed changeover and sequenced start/stop is measured and recorded at the factory. During on-site commissioning, the parameters can be entered as recorded, with no repeated trial and error.
Photos & enclosure construction
Below are photos taken in our own shop — from the complete unit down to the internal busbars and secondary wiring. Every build detail can be checked item by item.
Image key: 01–05 are shop photos (the numbers match the shot list). The line drawing shows the front elevation of the enclosure; dimensions match the specification table above.
Where these cabinets go
These are the routine applications — we can talk scheme and configuration directly. For the industry view, see the industry pages.
Workshop ventilation and dust collection
Start/stop control for supply and exhaust fans, dust collection fans and process exhaust in workshops.
Commercial and public building ventilation
Supply and exhaust ventilation for buildings, garage ventilation, and interfaces to the building management system.
AHU and fresh air units
Interlocked control of AHU fans, fresh air handling units and air dampers.
Boiler and kiln auxiliaries
Sequenced start/stop and interlock protection for induced draft and forced draft fans.
Tunnels and underground utility tunnels
Zone control and remote interlocking for jet fans and axial fans.
Mining and heavy machinery ventilation
Duty/standby and rotation control for underground and equipment room fans.
Commercial terms
Specification dated September 2026; quotations follow this.
| Drawings & design | Free |
| MOQ | 1 unit (5 or more recommended for production) |
| Production lead time | 15-25 days after drawing approval |
| on-time delivery | 98% |
| Warranty | 12 months |
| Loading port | Ningbo / Shanghai, China |
| Component brands | Schneider / ABB / Siemens / Chint |
| Factory visit & dispatch confirmation | Factory visits welcome; finished-cabinet photos and video before dispatch |
| Capacity | 5,800+ units / year |
Documents for your engineering team
Selection manual, outline dimensions and RFQ checklist — for the customer's electrical engineer. All three documents are being organized by product line; download links go live once complete.
Six questions procurement and electrical engineers ask most
Should a fan use star-delta or a VFD?
If you only need start/stop and airflow does not need to be regulated, star-delta is the most economical choice. If airflow must vary with operating conditions (adjusted by temperature, air pressure or CO concentration), use a VFD — energy savings are typically over 20%. The two can also coexist: VFD for the fresh air fan, star-delta for the standby/emergency fan.
How is a two-speed fan controlled?
Contactor combinations switch the motor's pole pairs to give high and low speed settings. During changeover, the control circuit first opens the current setting, waits for the speed to drop, then engages the other setting, with interlocking between the two to prevent phase-to-phase short circuits. The control panel usually provides local/remote and high/low speed selection.
Is damper interlocking mandatory?
It depends on the process. Starting a fan with the damper closed makes it run against blocked pressure, raising current and noise, which is hard on the motor over time. We default to a "confirm damper open, then start fan" sequence. If your system has normally open dampers or dampers controlled by another system, we can also do signal-only interfacing.
Can multiple fans share one cabinet?
Yes, but the enclosure size and incoming capacity must be designed for the total power, and the inrush from simultaneous starting must be calculated. With many fans, we recommend splitting cabinets by zone or using sequenced starting to reduce inrush.
What should be considered for rooftop or outdoor installation?
Raise the enclosure to IP65, point cable glands downward and seal them, add a rain hood on top, and add an anti-condensation heater inside. Rooftop temperatures are high in summer, so internal temperature rise must be calculated, with fans or a cooling unit added if needed.
Do you also build smoke exhaust fan controls?
The fan control cabinet itself is built to normal industrial and building ventilation requirements. If a fire smoke exhaust system is involved, the control cabinet must meet the applicable fire protection and acceptance requirements. Please state the project requirements in your inquiry, and we will match the supply scope to them.
Other cabinet types in the same main circuit
Related products use color-block placeholders for now (product photos not yet complete; they will be replaced together). Internal links will be filled in once live URLs are confirmed.
Fan tripping on start, or airflow that needs regulating?
Send us the fan type, power, quantity and control requirements, and we will provide a starting method and interlock solution free of charge · quotation within 24 hours. Direct from the source factory, MOQ 1 unit, 15–25 day delivery, 1-year warranty.
ISO 9001:2015 · CE(LVD+EMC) · CQC · IP65
When you write, include: single-line diagram or primary scheme, switch room layout, load list, and component brand requirements. You do not need complete drawings — capacity and cabinet type are enough to start.