The Fan Sits Millimetres From a 1000-Watt Heater

One order for the fan, the heater and the gap

An OEM building commercial HVAC heating modules asked for a complete fan heater assembly: a cross-flow blower and a 1000 W PTC element, quoted and drawn as one sub-assembly with the heater mounted directly at the discharge.

Meanwhile the envelope was unforgiving: an impeller no larger than 43mm across and 290mm long, in a housing profile near 60 by 60mm.

The working numbers

• First, 115 m3/h pushed through the PTC fins, which demand 22 Pa to cross without stalling the flow.
• Next, 230 V 50 Hz directly, with no room for a power supply.
• Meanwhile 37 dB(A) maximum, since the module serves occupied space.
• Finally, GB/T 13933 compliance, elevated ambient survival, and volume tier pricing for production scaling.

Why they bought the pair, not the parts

The heater block is 320mm long with a 290mm active zone, and the impeller is 290mm long. Naturally, those numbers match because someone matched them.

Otherwise, buy the two separately and that matching, plus the thermal consequences of proximity, lands on whoever integrates them. The customer chose to buy it solved.

Inside a fan heater assembly at 1000 watts

A fan heater assembly succeeds or fails in the few millimetres between the blades and the fins. Everything interesting happens there.

Why cross-flow carries the pairing

A PTC element heats unevenly if the air crosses it unevenly. The starved fins overheat and cycle their protection, while the flooded ones underperform.

By contrast, the tangential impeller delivers a ribbon of air exactly as wide as its 290mm length, matching the active heating zone edge to edge. A round jet from an axial fan would do precisely the wrong thing here.

Why the impeller is aluminum

Millimetres from a kilowatt of heat, the rotating part runs warm in operation and warmer at shutdown, when airflow stops but the PTC mass keeps radiating. In a fan heater assembly, that soak is the sizing case.

People miss it. A plastic impeller rated for the running condition meets its real test in the minutes after switch-off, so this build carries an aluminum impeller in a galvanized housing, sized for the soak rather than the datasheet ambient.

Why not a DC blower

Firstly, a 12 V DC centrifugal came up and got dropped fast. The customer rail is 230 V AC, and a power supply for the DC option costs money and volume the 60 by 60mm profile does not have.

Instead, the AC cross-flow architecture runs on the mains directly and holds the 37 dB(A) cap, which a small high-speed centrifugal would have struggled to do.

What one part number buys the customer

In a fan heater assembly, the interface between fan and heater has one owner, mechanically, thermally and aerodynamically. So when the module ships, the 22 Pa, the edge-to-edge coverage and the soak tolerance all get verified together, not hoped about separately.

Safety requirements for the fan follow GB/T 13933, and airflow verification follows ISO 5801 methods.

Technical Specifications

These figures describe the pair working together. Neither component meets them alone, which is the point of the assembly.

Parameter	Value
Fan Model	LWCA-43290SN-07
Airflow	115 m³/h
Static Pressure	22 Pa
Fan Input Power	19 W
Heater Power	1000 W
Speed	2300 RPM ± 10%
Fan Voltage	230V AC
PTC Voltage	220V AC
Frequency	50 Hz
Noise Level	37 dB(A)
Impeller Dimensions	43 mm x 290 mm
Housing Dimensions	370 mm x 60 mm x 60 mm
Operating Temperature	-25°C to +60°C
Bearing Type	Ball Bearing
Housing Material	Galvanized Sheet Steel
Impeller Material	Aluminum Alloy
Certifications	CE, RoHS, ETL, BSCI, CCC, UL, ISO

Technical Documentation

Here the following engineering files contain the approved specifications for mass production:

LWCA-43290SN-07 Fan Drawing
Provides the complete CAD dimensions for the 43×290 mm aluminum impeller and the 230V AC shaded pole motor housing for mechanical integration.

Visual confirmation of the client’s original product request, displaying the intended mounting position of the heater at the air outlet.

PTC Heater Drawing and Specs
Details the 320x35x12.5 mm footprint of the 1000W PTC component, including wiring instructions and GB/T13933-2008 safety compliance data.

Buying heat and air together

If your product pairs moving air with resistive heat, four decisions determine whether the fan heater assembly works.

• Buy the interface, not just the components. A fan heater assembly from one supplier makes the gap between blade and fin an explicit responsibility. Two purchase orders make it an assumption, and assumptions between suppliers fail at integration.
• Size the fan materials for shutdown, not just running. The hottest moment for the impeller arrives after switch-off, when the heater mass radiates into still air. Ask what temperature the rotating parts see in that soak, and choose the material against it.
• Match the airflow width to the active zone. After all, heater fins outside the airstream are dead weight, and fins in a starved corner are failure points. The impeller length should equal the active heating zone, which is a reason cross-flow dominates this product class.
• Interlock the heater to proven airflow. A kilowatt into still air is a hazard, so the element should only energize when the fan demonstrably runs. Decide whether that proof comes from a flow switch, a speed signal or the PTC element self-limiting behavior, and write it down.

See our cross-flow fans range, the AC cross-flow fans section, or cross-flow impellers.

Questions about fan-heater pairs

Why does a PTC element even need a matched fan?

Because a PTC self-regulates: its resistance climbs as it heats, so output depends on how fast air removes heat. Starve it and it derates itself; flood it unevenly and parts of it work while parts idle. The heater only delivers its rated watts across a properly matched airstream.

What happens to the fan when the heater switches off?

Simply put, the heater mass keeps radiating while the airflow that cooled everything stops. For the impeller sitting millimetres away, that soak is often the hottest condition in the whole duty cycle, which is why material choice keys to shutdown rather than steady running.

Could the fan run on after the heater stops?

Yes, and it helps: a run-on delay flushes the stored heat, and many controllers implement one. The assembly should still survive a hard stop, since power cuts do not wait for delays. Design for the soak, then add the run-on as comfort.

Is 37 dB(A) hard to reach next to a heater?

The heater itself is silent. However, its fins add resistance the fan must overcome without speeding into audibility. A wide, slow cross-flow impeller crossing the fins evenly reaches the pressure quietly, where a small fast blower would whine.