What a 5-Minute AHU Software Demo Should Prove Before You Commit

Most AHU selection software demos are run by the vendor, on a unit the vendor chose, at a duty the vendor knows works. You watch a finished selection appear and you learn almost nothing. A free trial is more useful — but only if you go in with a script, because the failure modes of these tools are not visible in a happy-path walkthrough.

Here is a five-minute evaluation you can run on any trial, using one duty you already know the answer to. Bring a unit from a job you have already built: 5 000 m³/h supply, 350 Pa external static, ePM1 60% final filter, 4-row heating coil, plate heat recovery. Real numbers you can check against a real data sheet.

Minute 1 — Enter one duty and watch what it refuses

Type the duty. Before you look at any result, look for what the tool declines to answer.

A selection engine talking to real supplier software will occasionally come back with nothing: no fan of that family fits that combination of flow, pressure and deck height. That is a correct answer. A tool that always returns a full, confident selection for every duty you throw at it — including a duty at the edge of physics — is interpolating from a curve fit, not asking an engine. Push the static to 1 800 Pa in a 700 mm deck and see whether the tool says "no viable fan" or quietly hands you one.

The same test applies one field down: ask for a fan article number that does not exist. A tool that returns a complete performance curve for NO-SUCH-FAN-XYZ is generating, not selecting.

Minute 2 — Ask where every number came from

Pick three figures on the result — a fan shaft power, a coil face area, an air density — and ask which supplier engine returned each one. The distinction matters more than it sounds:

What you see	What it should be	Warning sign
Fan efficiency	The supplier's published value at that operating point	A round number like 60% or 50% on every row
Air density	Computed from the stated air temperature, or the labelled ISO 5801 / AMCA 210 reference of 1.20 kg/m³ at 20 °C	1.2 printed beside air at 40 °C
Coil face	Solved by the coil engine, or the size you requested — labelled as which	A "standard" 1 200 × 600 that appears whenever the engine did not solve
Filter Δp	Read from the manufacturer's published points	A square law scaled from one anchor flow

A number the supplier never published should print as absent, with a reason — not as a plausible default. Our certified data vs curve fit article goes through how to spot the difference on a printed sheet.

Minute 3 — Make it disagree with itself

This is the highest-yield test in the whole demo and almost nobody runs it. Take the selection you just made and open three views of the same unit: the 3D or graphic view, the printed dimensional drawing (DXF or PDF), and the technical data sheet.

Then compare the overall length, the overall height and the section dimensions across all three. They should be identical to the millimetre. If the drawing shows a roof panel over a section that the 3D view leaves open, or the data sheet quotes a length the drawing does not, the tool is deriving dimensions in two places from two rules — and the fabricator builds from the drawing.

Minute 4 — Change one thing and watch what moves

Increase the filter class by one step. Then check three downstream numbers:

• the fan's total static (it must rise by the filter's added Δp),
• the internal SFP and the ECP-05-2026 class,
• the section length and therefore the overall unit length.

If the class letter does not move when the internal pressure drop rises meaningfully, the class engine is reading a stored value instead of recomputing. Same test with the air temperature: change the entering condition and confirm the density, the volume-to-mass basis and the heat recovery efficiency all move together.

Minute 5 — Print the dossier and read it as a consultant

Export the full document set. You are looking for four things: the operating point printed beside every result it produced, both winter and summer classes with the governing one stated, the ErP verdict shown separately from the Eurovent class (they are different regimes — one is EU market law, the other is a voluntary data-accuracy programme), and a dimensioned drawing that matches the model. The data sheet reading guide is the checklist a consulting engineer will actually apply to it.

The seven questions, condensed

1. Show me a duty where you return no fan.
2. Which engine returned this efficiency, and what prints when it returns nothing?
3. Where does this air density come from?
4. Do the 3D view, the DXF and the data sheet agree to the millimetre?
5. Change the filter class — does the SFP class recompute?
6. Where is the summer class, and which season governs?
7. Can I export the drawing and the BOM without asking you?

Five minutes, one duty you already know. Any tool worth buying will pass all seven, and will not mind being asked.

Run this test on a real selection →