Air Handling Units / Compact & Packaged AHUs / Buying Guide

Compact & Packaged AHUs: Buying and Engineering Guide

The selection focus is standardized configuration intended to reduce space and commissioning complexity. Unlike a household appliance, a commercial AHU is often project-configured. Check system duties and manufacturer selection output before comparing bids.

Procurement priority: Specify the design airflow, static pressure, heating and cooling schedule, outdoor-air share and system control sequence.

1. Airflow and Load Schedule

Verify that offered fixed module size reaches airflow and pressure duty point. Confirm the exact manufacturer’s selection sheet with full test conditions, dimension drawings and design assumptions. Require written responses to deviations in project specifications.

2. Fan and Coil Performance

Compare exact air connection orientation, service side and dimensions. Confirm the exact manufacturer’s selection sheet with full test conditions, dimension drawings and design assumptions. Require written responses to deviations in project specifications.

3. Casing and Filtration Design

Check preconfigured heat exchangers, fans and available factory accessories. Confirm the exact manufacturer’s selection sheet with full test conditions, dimension drawings and design assumptions. Require written responses to deviations in project specifications.

4. Heat Recovery and Environmental Limits

Review outdoor installation, noise, drainage and filter servicing. Confirm the exact manufacturer’s selection sheet with full test conditions, dimension drawings and design assumptions. Require written responses to deviations in project specifications.

5. Installation and Service

Assess delivery clearances and rigging through existing building openings. Confirm the exact manufacturer’s selection sheet with full test conditions, dimension drawings and design assumptions. Require written responses to deviations in project specifications.

6. Control, Testing and Handover

Confirm controls options, user interface, electrical protection and output signals. Confirm the exact manufacturer’s selection sheet with full test conditions, dimension drawings and design assumptions. Require written responses to deviations in project specifications.

7. Important Selection Warnings

Common mistake: Compact overall dimensions can hide inadequate maintenance clearance or fan pressure.

  • Choosing by maximum airflow without accounting for fan pressure and efficiency.
  • Omitting filter terminal resistance or access zones from the plant layout.
  • Overlooking hygiene, casing leakage, carryover and maintenance needs.
  • Equating a modular catalog family with one fixed as-sold assembly.

8. AHU Tender and Buying Checklist

  1. Certified air volumes and static pressure on final fan curves.
  2. Coil duty and air/water temperatures including frost conditions.
  3. Filter type, efficiency, pressure loss and service plan.
  4. Heat recovery, bypass, condensation and cross-leakage assumptions.
  5. Casing, insulation, dimensions, rigging and access clearances.
  6. Electrical load, fan controls, BMS and commissioning sequences.
  7. Acoustic data at the actual design duty point.
  8. Documentation, warranty, spares, factory and site acceptance tests.

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References

Use manufacturers’ latest configurator/submittal documents linked on AirAlign, the project mechanical schedule and ASHRAE ventilation standards as applicable.

AirAlign independent buying guide · October 2026. This article does not replace engineered AHU project selection.