AHU Selection Software for Sales Engineers: Quote in 5 Minutes

An AHU quotation is not a hard engineering problem. It is a long one. The physics of a 12 000 m³/h double-deck unit with rotary recovery has been settled for decades; what consumes the afternoon is everything wrapped around it — re-keying the same airflow into four supplier programs, redrawing the casing so the dimensions match the data sheet, and re-checking a Eurovent class after the customer moves the coil water temperatures by 5 K.

For a sales engineer carrying 15–30 live enquiries, that overhead is the whole job. So it is worth being precise about where the time goes.

Where the afternoon actually goes

A typical quotation, timed honestly, breaks down roughly like this:

Step	Manual / multi-tool workflow	What it should be
Enter duty, airflow, external pressure	5 min	2 min, once
Fan selection (supplier program)	15–25 min	Automatic, from the same inputs
Coil selection (second supplier program)	20–30 min	Automatic, circuits autosized
Heat recovery selection (third program)	15 min	Automatic
Sum pressure drops, re-run fan	15 min	Recalculated on every change
Casing layout + dimensions	30–45 min	Derived from the module list
Data sheet + drawing assembly	30–60 min	Generated
Eurovent / ErP check	15 min	Continuous

The pattern is obvious once it is written down: only the first row is engineering judgement. Everything below it is bookkeeping — and bookkeeping is where quotations get slow and where they get wrong, because each hand-off between programs is a chance for a number to be transcribed, rounded or forgotten.

The chained-pressure-drop step is the worst offender. Add a second filter stage, or move from ePM1 60 % to ePM1 80 %, and the clean-condition dP shifts by 30–60 Pa; the fan operating point moves; the absorbed power moves; the SFP moves; and the ECP-05-2026 class can flip. Done by hand across three programs, that is a 20-minute round trip for a change the customer described in one sentence.

The five minutes that matter

Compressing a quotation is not about typing faster. It is about removing the steps that never needed a human:

• One input set, many engines. Airflow, external static pressure, air and water temperatures and altitude are entered once and passed to every component engine. No re-keying means no transcription errors.
• Chained recalculation. When any component's air-side dP changes, the total is re-summed and the fan is re-selected in the same pass. The engineer sees the new operating point immediately, not after a manual loop.
• Autosized circuiting. Coil circuits should be derived from the tube velocity window (roughly 0.4–1.2 m/s for water) and the module stacking, not typed in from habit. Circuit count drives water-side dP, and water-side dP is what the customer's pump schedule is built on.
• Geometry as the single source of truth. The casing length, the connection positions and the drawing must come from the same model, so the DXF and the data sheet cannot disagree. Dimension drift between a drawing and a spec sheet is the single most common reason a technical data sheet gets rejected.
• Compliance evaluated continuously. Eurovent ECP-05-2026 classes (A+ to E) and the Ecodesign/NRVU requirements under (EU) 1253/2014 — with fan thresholds tightened by (EU) 2024/1834 through 2026–2027 — should be shown while the unit is being built, not discovered at the end.

Do those five things and the residual work really is a few minutes: describe the duty, look at what the engines returned, adjust the one or two things that are commercial decisions rather than physics, export.

What "fast" must not mean

Speed earned by approximating the components is not speed; it is rework. Fan and coil performance curve-fitted from catalogue points can sit several percent away from what the supplier's own engine returns at the same duty, and the customer's consultant will check against the supplier's data, not yours. Fast quoting only holds up when the numbers underneath come from the real supplier selection engines.

The other thing fast must not mean is unaudited. When a quotation is produced in five minutes, the dossier has to carry its own justification: which fan model, at which speed and absorbed power; which coil geometry, rows, fin pitch and circuits; which recovery efficiency at which reference conditions per EN 308 and EN 13053. That is what makes the quote defensible in a technical review — the audit trail, not the layout of the PDF.

The practical test

Next time an enquiry lands, time yourself on one thing only: how long it takes from receiving a changed requirement — "make it ePM1 80 %", "drop the water to 45/40 °C", "add 150 Pa external" — to having a fully re-checked unit with a new data sheet. If that number is measured in minutes, the tool is doing its job. If it is measured in coffee breaks, the tool is the bottleneck, not the enquiry.

Build a unit and export the dossier →