Single Inlet Centrifugal Blowers — OEM Manufacturer in China

Ningbo Longwell Electric Technology Co., Ltd. (LONGWELL) has been in HVAC&R air movement since 1990, sits in Yuyao, Ningbo, and ships to more than 30 countries. Buyers here are equipment makers who need a blower inside a cabinet — air purifiers, gas boilers and water heaters, fan coil units, enclosures — and importers sourcing a full size ladder.

What "single inlet" means

One inlet ring on one side of the scroll housing, one impeller. Air enters axially, turns 90°, is accelerated by the forward-curved blades and leaves through the rectangular outlet. The motor sits on the closed side, so the unit is narrower than a two-inlet blower on the same wheel diameter and needs clear intake on one face only — which is why it suits boxed appliances.

SISW (single inlet, single width) and SWSI (single width, single inlet) are the same arrangement written two ways. The large fans usually sold under those abbreviations, on a shaft and bearings in a welded housing, are a different product class. This is the OEM blower class: Ø120–315 mm, motor built into the impeller.

Sizes and catalogue data

The range falls in three size bands. Each link opens the model-level pages on our selection site, where every model has its own P-Q curve and CAD.

Catalogue data from the 2026 LONGWELL AC, DC and EC single inlet forward-curved catalogues. Each row spans a family, and the airflow and static pressure columns are two separate ends of one curve — they never occur together. The IP and insulation values (IP54 and class F on AC, IP54 and mostly class B on DC) are catalogue design ratings, not third-party certifications; an individual model's approved datasheet can differ, so we confirm both per model. The model that goes on the order is the one checked against your duty point — airflow, static pressure, supply voltage, control mode — then validated in your own cabinet before the first production run.

AC, DC or EC

AC

Single-phase 230 V or three-phase 380 V, capacitor run. A 140 mm example, LWFA2E140-092SS-01: 230 V, 148 W, 0.67 A, 2,400 rpm, 5 µF run capacitor, 65 dB(A), its curve running to 446 m³/h at the open end and 378 Pa at shut-off. On a tapped motor the datasheet fixes the speeds instead — the 133 mm single inlet sheet lists 1,600, 1,100 and 800 rpm, and the tap you wire decides the duty. On that model the thermal protector opens at 150–160 °C.

DC

Brushless, 24 V, 48 V or 310 V DC, 0–10 V speed input, 28 models from Ø120 to Ø180 — the usual answer when the appliance already has a DC bus. Worked example, bearings and life figures: DC brushless blowers.

EC

Electronically commutated, speed set by 0–10 V or PWM, 21 catalogue models Ø120–250. A 150 mm EC model turns about 2,550 rpm on a 10 V input, its curve reaching roughly 575 m³/h at the open end and about 410 Pa at the closed end. At sustained part load an EC build pays for itself; at one fixed duty an AC motor on the right tap is cheaper and just as good, so send the duty cycle, not only the maximum point. More on the EC centrifugal blower page.

Reading a single inlet model code

Codes run LW + F (forward-curved) + A, D or E (AC, DC or EC) + pole or phase code + impeller diameter + rotor size + structure letter + voltage letter + serial number. Here the structure letter is always S, single inlet with housing; the voltage letters are T (380 VAC) and S (230 VAC) on AC, M (24 VDC), H (48 VDC) and Z (310 VDC) on DC. RS485 is offered on the 102, 138 and 188 rotors only, which rules out the smallest frames if you need bus control. So LWFA4D250-138ST-01 is a 250 mm three-phase 380 V single inlet blower on a 138 rotor. Full decode on the centrifugal blower hub; bare impellers and housings on the blower wheels and impellers page.

One inlet or two

On the same wheel diameter the two-inlet build moves far more air, in a wider housing needing clear intake on both faces; the single inlet package is narrower and seals against one cabinet wall, which usually decides it. Full comparison on our main site: single inlet vs double inlet centrifugal fans. The two-inlet models sit on the forward-curved squirrel cage blower page.

How these blowers are built and inspected

One line on sourcing, because buyers ask: this range is engineered and specified by LONGWELL, built to LONGWELL drawings and inspected to LONGWELL standards — the full account is on the China centrifugal blower manufacturer page. In practice, a bracket, a lead-out or a supply voltage is a drawing revision we make ourselves.

The company’s motor winding line and cross-flow fan production run in Yuyao (factory); these blowers are built to LONGWELL drawings in qualified partner plants. Outgoing checks here are earth continuity, dielectric withstand, insulation resistance, a run test, and impeller balance to the grade on the drawing. Air performance is tested to the AMCA 210 method; sound is measured in a semi-anechoic room, calibration report SSD202500326.

Certificates for this range

• CE, AC forward-curved: KTS certificates LVD KB2207084L01, EMC KB2207085E01 and RoHS KB2207086R01 cover LWFA108 to LWFA450, so the AC single inlet models here (Ø120–315) are inside that scope. They do not extend to the EC or DC models.
• ETL: part of the EC and DC forward-curved range is an ETL Recognized Component under Intertek control number 5022563, inside the report's model rule and power ceiling (DC: 600 W at 48 V, 500 W at 24 V, 200 W at 12 V). Send the exact model and we confirm coverage in writing before quoting.
• Management systems: ISO 9001, ISO 14001 and ISO 45001 — numbers and validity on quality and certifications.

We do not stretch a certificate to a model it does not cover, and we hold no third-party IP certificate. If your market needs an approval we do not hold, say so early — it changes the timeline.

Samples, lead time and what can change

Samples of catalogue models ship in 1–3 days, production runs in 15–30 days, warranty is 12 months. Tell us what has to change and it is priced into the quote: supply voltage, speed setting or control interface, lead and connector, mounting and bracket, nameplate and packing. How a project runs from drawing to first shipment is set out in the OEM process. Neighbouring ranges: all centrifugal blowers and gas and combustion blowers.

FAQ

Can you build a single inlet centrifugal blower to my drawing?

Yes. Send the drawing, or just the duty point — airflow, static pressure, supply voltage, control mode — with the space envelope and the mounting. We answer with the nearest catalogue model first, because that is the fastest route to a sample, and quote a modified version beside it.

What sizes and duty points are available?

Impellers Ø120–315 mm. AC reaches 5,150 m³/h and 695 Pa, DC 762 m³/h and 773 Pa, EC 1,957 m³/h and 989 Pa — each figure is the end of a curve, so read them as family limits, not as a working point.

Is a single inlet blower the same as an SISW or SWSI fan?

The arrangement is the same: one inlet, one impeller width. Those abbreviations normally describe large fans with a shaft, bearings and a welded housing — a different product from these Ø120–315 mm OEM blowers. Give us the size and we will say whether it is in range.

How much of the housing can you change?

Anything inside the existing tooling is a drawing revision: outlet flange detail, inlet ring fixings, bracket, lead-out, nameplate. A new housing width or impeller size needs new tooling, quoted separately with its own sample lead time.

What is the MOQ, and how fast is a quote?

MOQ is set per model and confirmed with the quotation, because it depends on whether the build uses catalogue tooling or new tooling. Technical answers and quotes normally go out the next working day.

Ask for a quote — send the duty point, the opening the blower must sit in, and which face of the cabinet is free for intake. You get back the nearest single inlet model, its curve, the sample lead time and the price.