SectionsCompact air handling units
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Compact air handling units

Compact describes packaging and installation space. It does not establish the number of air paths or which treatment functions the unit includes.

Principle and scope

A compact unit puts a defined combination of functions into a relatively small enclosure. It can be supply-only, extract-only or two-stream with recovery. A box fan is one possible assembly; it is not the definition of every compact AHU.

Compare the complete installed envelope, including ducts, drainage and filter access. A smaller casing may increase internal air velocity, pressure loss and sound; suitability depends on the measured selection data.

Installed space and actual duty

Check the fan curve at the required pressure, filter condition and selected accessories. Verify permitted mounting orientation, access-panel swing or removal, filter withdrawal, flexible connectors and condensate fall. A ceiling void that fits the bare enclosure may still be too small to install and service the unit.

Related components: Fan · Air filter

Calculate the stated air duty. It does not establish whether a compact unit fits, has the necessary functions or meets its operating limits.

Calculate sensible air load

Sensible air load calculation

Calculate the heat rate associated with a specified temperature change in one air stream. Enter all five values for your stated operating conditions.

Mass flow ṁ = ρ × V̇ / 3600; temperature change ΔT = Tout − Tin; sensible heat rate Q̇ = ṁ × cp × ΔT. With the units below, the result is in kW. Positive Q̇ means heating; negative Q̇ means cooling. Zero flow or zero temperature difference gives zero sensible load.

For a steady, single-phase air stream with constant user-supplied properties. The balance excludes latent heat, moisture changes, phase change, shaft work and kinetic/potential energy changes. It does not select a fan, coil or complete AHU.

Topic for the local draft

Opening a page does not select anything. A topic choice records context only; no product or configuration is selected.

Operating inputs

Use density at the same state and volume basis as the entered airflow. Enter cp in kJ/(kg·K), not J/(kg·K). Density and cp are editable assumptions; no universal values are prefilled. Check that your temperatures and properties describe gas-phase air. This tool does not check phase boundaries or property-table consistency.

Interactive calculation requires JavaScript. The formula, units, scope and reference information remain available here for manual use.

Heat recovery

A compact two-stream unit can integrate recovery, filters and fans in one housing. Assess access to the exchanger and both filter banks, drain arrangement and all four air connections. Small dimensions do not establish separation quality or winter performance.

Related components: Fan · Air filter · Condensate drainage

Commissioning and service

Before closing the ceiling or enclosure, demonstrate filter removal, access-panel opening and drain inspection. Measure the actual operating flow and room sound. Record the orientation and accessory set; changes to filters or duct fittings can move a small fan away from its selected operating point.

Related components: Fan · Air filter · Condensate drainage

Back to section: Compact

A guide to equipment and selection; the final configuration and performance require project-specific confirmation.