Sourcing humidity controllers from China

Duty on automatic humidity controllers

Read from the UK Trade Tariff on 18 October 2026, heading 9032 covers automatic regulating or controlling instruments and apparatus. This guide concerns humidity controllers that operate equipment to maintain a humidity setting. For the wider product family, see thermostats and controllers. The table separates electronic and mechanical versions sharing the same residual code.

Goods from China under 9032 89 00 90 and controller parts under 9032 90 00 90 carry 2% duty. Hydraulic or pneumatic instruments under 9032 81 00 00 carry 0%. These lines show no anti-dumping or countervailing duty and no suspension. Suspensions elsewhere in the heading concern specifically described steering, valve and gas-flow products, rather than ordinary humidity controllers.

The UK Trade Tariff attaches an import control of fluorinated greenhouse gases to these lines. Confirm the requirement and applicable declaration with your customs broker for the actual goods; do not assume the tariff attachment means every standalone controller contains refrigerant. Confirm the commodity code from its operating principle, supplied components and whether it arrives separately or within a machine.

Specify sensing and humidity switching

Specify the humidity range, declared accuracy, switching differential, calibration method and operating temperature. Choose an integral or remote sensor and agree its cable length, mounting position and protection against condensation. State whether rising humidity starts extraction or dehumidification, or falling humidity starts humidification. Agree the response to a disconnected sensor and restoration of power.

Match the supply, relay rating and load type to the actual fan, humidifier or dehumidifier. Distinguish a control signal from an output intended to power the load. Ask for the wiring diagram, enclosure dimensions, mounting details and replacement-sensor specification. Approve a sample on the equipment your customers will use.

For Great Britain sales, mains-powered models within the electrical safety rules need conformity checks, importer identification and understandable English instructions. For electronic models, check the scope of electromagnetic compatibility and hazardous-substance rules and obtain supporting evidence where applicable. Confirm with the relevant authority whether waste electrical equipment obligations apply to the supplied controls. Use testing and certification to settle the evidence for the exact model.

Worked duty example

Illustrative example, not a quote: Illustrative batch of automatic humidity controllers for an installation business under 9032 89 00 90, invoiced at £10,000 free on board, with £900 of freight and insurance to the UK. The customs value is £10,900. Duty at 2% is £218. Import VAT at 20% is charged on the customs value plus duty, £11,118, so it is £2,223.60. Import taxes total £2,441.60; a VAT-registered importer can usually reclaim the VAT, so the lasting cost is the £218 of duty. The import duty and VAT guide explains each step.

Inspection checklist

Sensor accuracy: compare readings with a calibrated humidity reference across the agreed operating range after stabilisation. Record deviations and repeat after exposure to the intended environment.

Switching behaviour: raise and lower humidity through the set point, record the switching differential and verify the correct output direction. Test sensor disconnection and power restoration.

Load and construction: operate the agreed load, check relay chatter and heating, and inspect terminal security, probe connections, enclosure cracks and moisture protection.

Identity and documents: match model, supply and load ratings to the approved sample and reports. Check importer details and English instructions where the electrical safety rules apply. Arrange quality inspection before shipment and repeat functional checks on arrival.

What goes wrong

A controller can display plausible humidity while switching at the wrong point. Sensor drift, condensation and poor placement can produce unstable readings. Reversed humidifying and dehumidifying settings can make the controlled equipment worsen the problem. A narrow switching differential can cause repeated cycling.

A relay rating quoted for a different load can conceal poor suitability for a motor or compressor. Replacement probes may use incompatible sensing characteristics, and reset behaviour may leave equipment running after a fault. Put the agreed load, probe identity and fault response into the purchase specification, then test production samples against it.

Cambridge China Bridge sources these products for UK businesses, checking the factory and the documents before shipment. See factory verification. For components and parts, see sourcing for manufacturers.