Sizing selects the aroTHERM plus rung nearest PSR ~0.8 (0.8 x design heat
loss) — the Appendix-N efficiency peak, reproducing the pump a real
installer fits — rather than the MCS PSR>=1.0 capacity target, which
oversizes. Validated against the relodged Elmhurst ASHP cert (delta 0
held at the 5 kW Vaillant); the two self-snapshot pins re-pin to their
correctly-sized larger pumps, and the orchestrator/harness thread the
calculator's design heat loss so production sizes to the dwelling. Manual
SapResult test stubs carry the new design_heat_loss_kw field.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>