Manual S equipment selection
Manual S equipment selection and heat pump sizing that fits the house
Manual S is the ACCA method for choosing heating and cooling equipment once the Manual J load is known. It checks capacity at the actual design conditions, not the nameplate, and limits oversizing. Tradewright applies Manual S to real equipment, including cold-climate heat pump capacity at your design temperature, during the sales visit.
Cold-climate heat pump, 3 ton
33,100 BTU/h at 2°F · 86% of load
Cold-climate heat pump, 3.5 ton
38,900 BTU/h at 2°F · 101% of load
Standard heat pump, 3 ton
19,800 BTU/h at 2°F · needs 18,600 strip heat
Gas furnace 80k + 16 SEER2 AC
Meets load · highest 15-year cost
How equipment selection works
Step 1: Start from the load
The room-by-room Manual J heating and cooling loads, and the design temperatures behind them, carry straight into selection.
Step 2: Check real equipment
Candidate units are checked on their capacity at design conditions, so a heat pump is judged on what it delivers on the coldest design day.
Step 3: Apply Manual S limits
Equipment that is too small, or oversized beyond Manual S limits, is ruled out, and the reason is recorded.
Step 4: Hand off to comparison
The units that fit move into the whole-system comparison and the Good/Better/Best proposal.
Who it helps
Heat pump contractors
Size cold-climate heat pumps on capacity at design temperature, not nominal tons.
Comfort advisors
Recommend equipment with an engineered reason, without memorizing performance tables.
Technical leads
See which units were considered and why each one was accepted or ruled out.
Boiler and furnace replacements
Stop replacing like for like when the existing unit was oversized from the start.
Rebate jobs
Produce an equipment selection sheet to go with the Manual J report.
Equipment selection compared
| Rules of thumb | Load-calc-only tools | Tradewright | |
|---|---|---|---|
| Sized from a Manual J load | No | Yes | Yes |
| Capacity checked at design temperature | No | Some | Yes |
| Manual S oversizing limits applied | No | Some | Yes |
| Shows ruled-out equipment and why | No | No | Yes |
| Flows into a priced proposal | No | No | Yes |
Columns describe software categories and common practice, not specific vendors.
Questions
What is Manual S?
Manual S is the ACCA procedure for selecting residential heating and cooling equipment. It takes the Manual J load and checks equipment capacity at the actual design conditions, with limits on how far equipment may be oversized or undersized.
How does Tradewright size a heat pump?
Tradewright compares the Manual J heating and cooling loads with each heat pump's capacity at your design temperature, rather than its nominal tonnage. Units that cannot carry the load, or that exceed Manual S limits, are ruled out with the reason shown.
Does it handle cold-climate heat pumps?
Yes. Cold-climate heat pump selection is checked on capacity at the design temperature for the location, which is where nominal ratings are most misleading.
Which equipment types can it select?
Heat pumps, mini-splits, furnaces, air conditioners, boilers and dual-fuel systems.
Can I see why a unit was rejected?
Yes. Ruled-out equipment stays visible with a short explanation, such as insufficient capacity at design temperature or oversizing beyond Manual S limits.
Can I still choose a different unit?
Yes. Tradewright engineers the options; you decide how to sell. Your team can review the selection and adjust it before the proposal is built.
Related tools and guides
See heat pump sizing at design temperature on a real home.
A 20-minute demo on a real home in your territory.