Glossary · Heating, cooling & ventilation

Manual S (ACCA equipment selection)

Also called: ACCA Manual S · ANSI/ACCA 3 Manual S

The US industry standard for choosing heating and cooling equipment whose real capacity, from the maker's data, fits the home's calculated loads.

What it means

Manual S takes the heating and cooling loads from Manual J and the manufacturer's performance data, then checks that a candidate system falls within size limits that account for the local climate. The 3rd edition (ANSI/ACCA 3 Manual S – 2023) expanded the size tolerances for variable-capacity heat pumps. It covers heating, cooling, dehumidifying and humidifying equipment.

Why it matters in an audit

It's the step that stops a too-big or too-small unit from being installed even after a proper load calculation.

Typical numbers

Reference values with their sources. Your auditor’s report gives the figure for your own house.

What	Value	Source
Current edition	3rd edition (ANSI/ACCA 3 Manual S – 2023), with 2024 addenda	acca.org ↗

Sources

acca.org ↗

Related terms

Manual J (ACCA load calculation) The US industry standard for calculating how much heating and cooling a house needs, room by room, so equipment can be sized correctly.
Manual D (ACCA duct design) The US industry standard for designing and sizing a home's ducts so each room gets the airflow the heating and cooling equipment is meant to deliver.
Load calculation An engineering calculation of how much heating and cooling a house needs, room by room, used to size equipment correctly.
Oversizing Installing heating or cooling equipment with much more capacity than the house needs, usually from rules of thumb, not a load calculation.
Variable-speed (inverter) compressor A compressor that ramps its speed up and down to match the heating or cooling needed, instead of switching fully on and off.

← Every term, A to Z