# Manual S: select an HVAC system from design-condition performance

Canonical: https://www.savpwr.com/knowledge/manual-s-selection
Market: United States
Author: SAVPWR Editorial (VDX Logic LLC)
Published: 2026-11-09
Sources checked: 2026-11-09

## What should happen after the load calculation?

The contractor should select actual equipment using the calculated loads and manufacturer performance at relevant operating conditions. A nominal capacity or a high efficiency label does not complete equipment selection.

## Translate the load into a selection

ACCA Manual S addresses residential equipment selection. The comparison needs sensible, latent and heating output where applicable. Manufacturer expanded data can differ from the standardized performance point shown on a certification record. [1][2]

## For heat pumps, ask about both seasons

Cold-climate selection needs the winter load and low-temperature capacity, while summer comfort still matters. Ask how minimum output, humidity and backup heat are considered. A design aimed at covering winter heating should explain its cooling-season operation rather than ignoring it. [2]

## Turn a product recommendation into a reviewable proposal

Ask for exact outdoor, indoor and control components and the performance data supporting the choice. Record which data were unavailable. If the bidder changes the model after approval, request an updated selection rather than accepting a brand-family substitution.

## Decision exercise

A hypothetical home needs 28,000 Btu/h of total cooling at its design conditions. A product called a 3-ton system is not automatically confirmed to deliver the needed sensible and latent capacity there. Ask for the operating-condition table and selection record rather than assuming a nominal 36,000 Btu/h settles the issue.

Numbers are illustrative assumptions, not forecasts.

## Preparation checklist

- Compare selected equipment with the load report.
- Request summer and winter design data.
- Track exact model and control substitutions.

## Is Manual S the same as an AHRI certificate?

No. A certificate documents a rated combination; selection checks whether equipment performance suits the design requirements of the home.

## Sources

[1] ACCA — Manual S Residential Equipment Selection: https://www.acca.org/standards/technical-manuals/manual-s
[2] PNNL — Cold Climate Heat Pump Sizing and Selection: https://basc.pnnl.gov/resource-guides/cold-climate-heat-pump-sizing-and-selection

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