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SAP 10.2 Appendix D §D2.1(2) Equation D1 blends the monthly water-heater efficiency by the ratio of the boiler's space-heating load to its water load. On a dual-main cert the DHW boiler does only its OWN share of space heating ((204) for Main 1, (205) for Main 2), but the cascade fed Eq D1 the dwelling total ((202) = 1 − secondary). That over-weighted η_winter and under-stated HW fuel — simulated case 6 (Main 1 serves DHW + 51% of space heat) was HW −78 kWh vs the worksheet. New `_water_heating_main_space_fraction` returns the DHW main's total- space share via `_water_heating_main` (WHC-901 → Main 1 (204); WHC-914 → Main 2 (205)); single-main / WHC-901 single systems get (202) = 1 − (201), so they are unchanged. Case 6 (219) HW now 4902.8601 EXACT. With S0380.205 (demand exact), case 6 now closes to 1e-4 on EVERY metric: SAP cont 71.6597, ECF 2.0316, cost 1162.5374, (211)+(213) 14736.9564, (219) 4902.8601, (231) 356, (232) 357.6571, CO2 5953.6679 (rating) / 4895.2137 (demand). Re-pin: 0240 (dual combi, WHC 901, Main 1 51%) HW rises slightly → PE +1.6893 → +1.8687, CO2 +0.0815 → +0.0907 (SAP 72 unchanged). Single-main certs unchanged (2360 pass + 0 fail). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> |
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| .. | ||
| addresses | ||
| fuel_rates | ||
| property | ||
| property_baseline | ||
| sap10_calculator | ||
| tasks | ||
| __init__.py | ||
| test_postcode.py | ||