AirSelect3D Blog
AHU engineering, selection
and compliance — explained.
Practical articles on air handling unit selection, component data, specific fan power, heat recovery and acoustics. Engineering examples need checking against the applicable standards and project requirements.
Dampers and Mixing Sections: EN 1751 Leakage and Actuator Sizing
EN 1751 damper leakage classes, actuator torque sizing in Nm/m², and the pressure drop a mixing section quietly adds to an AHU's internal total — and to its SFP.
Fan Performance Curve or Fitted Parabola? How to Tell in AHU Software
A fan curve drawn as p = a − bQ² looks convincing and can be 30 % wrong. Four tests that show whether your AHU selection software reads the supplier's published line.
AHU Bill of Materials + DXF/IFC Export: What Your BIM Team Needs
A bill of materials is the export nobody specifies and everybody uses. What an AHU BOM must carry, how it ties to the DXF and IFC, and the checks that keep all three telling the same story.
AHU Software Demo Checklist: Test Your Own Project
Prepare a demonstration around a known unit, reference data, revisions and the documents your team needs.
AHU Selection for Sales Engineers: Review the Quotation Workflow
Reduce repeated data entry while preserving engineering review and a clear record of quotation assumptions.
Web-Based vs Desktop AHU Selection Software: The End of ClickOnce
Why installer-based AHU selection tools are being replaced by browser-native ones — what ClickOnce actually was, what breaks it, and where the vendor DLLs live now.
Manufacturer Data and Calculation Models in AHU Selection
Understand data sources, interpolation, operating ranges and validation when reviewing an AHU selection workflow.
How to Read an AHU Technical Data Sheet: A Consulting Engineer's Guide
A reading order and five pieces of arithmetic that let you verify an AHU technical data sheet yourself — SFP, coil duty, heat recovery efficiency, pressure budget and acoustics.
Humidification in AHUs: Steam vs Adiabatic and VDI 6022 Hygiene Rules
Steam and adiabatic humidification solve different problems in an AHU — energy use, saturation distance and hygiene risk under VDI 6022 all drive the choice. Here's how to spec it correctly.
Night Purge, Free Cooling and Mixed-Air: AHU Control Modes to Spec
Night purge, free cooling and mixed-air economizer modes each demand different damper authority, leakage class and fan turndown — what your AHU spec must state to make them work.
The Real Cost of Oversizing an AHU: Capex, Footprint, Part-Load SFP
Going one casing size up cuts SFP, but oversizing past that point adds capex and footprint faster than it saves — and hurts twice at part load. Worked numbers.
Plate HRS Frost Protection: Preheat vs Bypass vs Modulation
Frost protection for plate heat recovery compared — preheat coil, full bypass and modulating control, with the seasonal energy cost of each strategy priced out.
From SFP Class to Euros — Annual Fan Energy Cost and Payback
Convert SFP_int into annual kWh and euros: the Δp/η identity, a 5 000 m³/h worked example, and how to justify one casing size up to the building owner.
AHU Airflow Arrangements — Stacked, Side-by-Side and Cross-Flow Bridges
How supply/extract routing decides AHU footprint, height and duct connection sides — stacked vs side-by-side layouts, cross-flow bridges and deck-scoped keys.
AHU Airflow Sizing: From Heat Load (kW) to Supply-Return ΔT
How the sensible heat equation converts a calculated heating or cooling load into the airflow an AHU must deliver, and how supply-return ΔT is chosen.
What BIM Coordinators Actually Need From an AHU Export (DXF vs IFC, LOD, Clash)
A BIM coordinator's view of AHU exports — when DXF is enough, when you need IFC, what LOD 300 vs 350 requires, and how connection points survive a clash check.
Cooling Coil Selection: Rows, Circuiting, ADP and Carry-Over Limits
How row count, circuiting, apparatus dew point, bypass factor and carry-over velocity interact in AHU cooling coil selection, with a worked sizing example.
EC Plug Fans vs Belt-Driven: Efficiency, Redundancy, ErP Implications
EC plug fan walls vs belt-driven centrifugal fans in AHUs - efficiency at part load, N+1 redundancy, maintenance, and the 2026/2027 ErP fan ecodesign angle.
Psychrometrics for Sales Engineers — The Five State Points Every AHU Quote Implies
The five psychrometric state points behind every AHU quote - outdoor, return, mixed, coil-leaving and supply air - with a worked example and the numbers a consultant checks.
From Selection to BIM — What a Clean DXF/IFC Hand-off Looks Like
What consulting engineers and BIM coordinators actually need from an AHU selection tool's DXF/IFC export — accurate dimensions, connection points, and no stale geometry.
Duct Connection Design — Damper Apertures, Velocities, and the Lost 50 Pa
How duct connection sizing, damper aperture position and deck-scoped routing quietly add 50 Pa to an AHU quote — and how to catch it before install.
A 3D Workflow for AHU Selection: What to Evaluate
Review a 3D AHU workflow through layout, operating conditions, revisions and generated documents.
Heating Coil Selection — Rows, Fin Pitch and the Air-Side dP Trade-Off
How row count, fin pitch and tube velocity trade off against air-side pressure drop in AHU heating coil selection, with real circuit-sizing numbers.
AHU Selection Projects: Define the Market Requirements
Prepare an AHU software brief around the destination market, applicable requirements and expected documentation.
Evaluating a Web-Based AHU Selection Workflow
A practical checklist for evaluating browser-based AHU layout, component data and document exports.
AHU Selection Software: A Practical Evaluation Framework
Evaluate an AHU selection workflow using your own unit, component data, documents and project requirements.
Reviewing an AHU Technical Data Sheet: A Practical Checklist
Review operating conditions, component sources, geometry and document revisions in an AHU technical data sheet.
Octave-Band Sound Power in AHUs — How LwA Totals Are Really Summed
How octave-band sound power levels are logarithmically summed and A-weighted into the LwA figure consultants ask for - with a full worked example.
Plate vs Rotary Heat Recovery: Efficiency, Leakage, Frost Strategy
Plate vs rotary heat recovery compared on EN 308 efficiency, EN 13053 leakage classes and frost risk — a climate-based selection guide for AHU sales engineers.
AHU Filter Classes After ISO 16890 — ePM1, ePM2.5 and ePM10 Explained
ISO 16890 replaced EN 779 - what ePM1, ePM2.5 and ePM10 really measure, and which filter class to specify for offices, hospitals and industry.
Face Velocity — the One Number That Sizes Your AHU Casing (and Your SFP)
Face velocity (v = q/A) drives casing size, coil selection, filter life and SFP in AHUs - target ranges per component and the real trade-offs.
How to Choose AHU Selection Software: An OEM Evaluation Checklist
Evaluate AHU selection software on a real unit: supplier data, 3D configuration, PDF and DXF outputs, revisions and the scope of your deployment.
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