120V EC Axial Fan for Air-Source Heat Pumps: 805 m3/h Case Study

What the heat pump OEM needed

A North American OEM needed an EC axial fan for the evaporator in a new residential air-source heat pump. The duty point was specific. Namely 805 m3/h at 16.7 Pa.

Power was the tight constraint. The request specified 25W maximum, with reluctant acceptance of 30W if that was what the airflow demanded.

The control requirement is the interesting part.

• A fixed 120V, 60Hz single-phase supply, since that is what homes there provide.
• A fixed-speed EC axial fan, explicitly excluding a VFD or any complex controller.
• The fan delivered from the factory pre-set to hit 805 m3/h exactly.
• A 250mm impeller on a square mounting panel, as drawn.
• At least IP44, since the unit sits outdoors.
• Lastly, performance data tested to AMCA 210/211 and ISO 5801.

That combination looks contradictory at first. The customer wants EC efficiency, yet refuses EC wiring. In fact you can have both together, and the next section explains how.

Setting the EC axial fan at the factory

Here the problem was hitting a precise airflow and pressure target with a motor that never varies its speed.

Why an AC motor could not do it

We ruled out a standard AC induction motor immediately, for two separate reasons.

Firstly, it cannot deliver the required flow inside a 30W budget. Secondly, its speed is tied to line frequency, so trimming it to an exact duty point needs a VFD, which the customer had explicitly forbidden.

The trick with a SmartEC motor

Our LWAE3G 250 platform solved it. The motor has full 0-10V and PWM variable speed capability. Moreover, its integrated controller can be factory-programmed to one fixed RPM instead.

That gives exactly what the customer asked for. EC efficiency, with no control wiring on their side at all, since we make the speed decision before the fan leaves us.

Setting the speed

Our engineers picked the LWAE3G250US-7PYW-17-00. Its curve at the nominal 1650 RPM comfortably exceeds the duty point, which is the right starting position.

A light development task then trimmed the factory-set speed until the fan produced exactly 805 m3/h against 16.7 Pa. Consequently the final solution landed on the original 25W target rather than the 30W fallback.

Rated beyond the requirement

The fan ships IP55 rather than the IP44 requested, so it resists water and dust better at no extra cost. Meanwhile maintenance-free ball bearings and a -25C to +60C range cover a North American winter, which a heat pump evaporator meets every year.

Technical Specifications

Meanwhile the maximum figures below sit well above the duty point we set this EC axial fan to. That headroom let us trim the speed rather than push it.

Technical Documentation

The PDF contains the full technical data, P-Q performance curve, wiring diagram, and mechanical drawings for the LWAE3G250US-7PYW-17-00, essential for design engineers integrating the fan into the heat pump chassis.

Download Technical Specification: LWAE3G250US-7PYW-17-00

Here the product family overview shows the LWAE-250 series in its standard configuration, from which the customer-specific model was derived.

Why the OEM chose this route

On a project like this, four things counted.

• Light development, not full NPI. A full custom NPI takes 90 days. Because this needed only factory programming of a standard SmartEC motor, production-intent samples at the fixed duty point arrived in under four weeks.
• EC efficiency at a workable price. Residential heat pumps are a volume market, and an expensive fan simply does not get designed in. Producing the EC axial fan and its motor ourselves is what put this efficiency inside the customer budget instead of above it.
• Margin given away for free. IP55 instead of IP44, plus a -25C threshold, exceed what the brief asked for. That margin raises field reliability in harsh weather, and it costs the customer nothing.
• Data before the samples. We sent a full documentation package with performance tested to ISO 5801 early. Consequently the customer engineering team could commit with confidence rather than validate first.

Browse our EC axial fan range, or the condenser and heat pump fan series. Test methods are published by AMCA International.

Questions about speed and certification

Can the speed be adjusted in the field?

Not as delivered, since this one was factory-programmed to a fixed 1650 RPM at the customer request. The underlying SmartEC motor is fully controllable though, with 0-10V and PWM inputs available if you connect a compatible controller. For other fixed-speed applications we set whatever RPM you need during production.

What is the lead time on 500 units?

Mass production runs 15 to 30 days after the purchase order is confirmed for a standard model like this. Samples are usually available within one to two weeks, which is what keeps an aggressive launch timeline realistic.

Is it UL certified for North America?

Here the base motor platform is designed to comply with UL 1004-1, and the fan assembly with UL 507. This project baseline was CE marked. Achieving full UL recognition for a specific customer configuration is a routine process here, and our experience with North American certification shortens it.

Why is factory-setting the speed better than a field controller?

Because it removes a whole layer of the installation. No control wiring, no potentiometer, no commissioning step, and nothing an installer can set wrongly. Where the duty point never changes, all of that adds cost and risk. Meanwhile it adds no capability at all.