Slice 102f-prep.7: Table N4 fixed durations ("24"/"16") in HP extended-heating helper

SAP 10.2 Appendix N3.5 Table N4 (PDF p.107) — heat-pump packages
with fixed daily heating durations:
  - "24" → N24,9 = 365 (continuous): every day at heating temperature,
    no off period → (days_in_month, 0) per month → MIT_zone = Th.
  - "16" → N16,9 = 365 (unimodal, 0700-2300): every day with single
    8h off → (0, days_in_month) per month → MIT_zone = Th − u1(8h).
  - "9" → standard SAP schedule (bimodal 7+8 off): falls through to
    `None` so the orchestrator applies the legacy bimodal path.

Cert 9418 (Daikin Altherma EDLQ05CAV3, PCDB 102421) lodges
`heating_duration_code = "24"` — worksheet (87) MIT_living = 21.0
every month (= Th1, no off period) and (90) MIT_elsewhere collapses
to Th2 directly. Pre-fix the bimodal cascade produced MIT ~17.8-19.8
(2.04°C low at Jan) and SAP was +2.20 over worksheet 84.6305.

Post-fix cert 9418 closes to SAP Δ +0.0296 (from +2.20) — the
residual is consistent with the same ~0.05 PSR-formula drift seen
in 5/7 cohort certs sharing PCDB 104568.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/documents_parser/tests/test_summary_pdf_mapper_chain.py

@@ -678,6 +678,43 @@ def test_api_0380_heat_pump_no_pumps_fans_kwh_per_table_4f() -> None:
     assert result.pumps_fans_kwh_per_yr == 0.0
 
 
+_API_9418_JSON = (
+    Path(__file__).parents[3]
+    / "domain/sap10_calculator/rdsap/tests/fixtures/golden"
+    / "9418-3062-8205-3566-7200.json"
+)
+
+
+def test_api_9418_daikin_24h_duration_mean_internal_temp_matches_worksheet_92() -> None:
+    # Arrange — cert 9418 (Daikin Altherma EDLQ05CAV3, PCDB 102421)
+    # lodges `heating_duration_code = "24"`. Per SAP 10.2 Table N4 (PDF
+    # p.107) this means N24,9 = 365 (all days operate at 24-hour
+    # heating, no off-period). Worksheet (87) MIT_living = 21.0 every
+    # month (= Th1, no off period), worksheet (90) MIT_elsewhere
+    # collapses to Th2 directly. Worksheet (92) blended at fLA = 0.30.
+    #
+    # Pre-slice-102f-prep.7 the helper's "V"-only gate returned None
+    # for this duration → bimodal cascade gave MIT ~17.8-19.8 (off by
+    # ~2°C). After Table N4 wiring the cascade lands at 1e-3.
+    doc = json.loads(_API_9418_JSON.read_text())
+    epc = EpcPropertyDataMapper.from_api_response(doc)
+
+    # Act
+    inputs = cert_to_inputs(epc, prices=SAP_10_2_SPEC_PRICES)
+
+    # Assert — worksheet (92) "MIT" 12-tuple at 1e-3 per month.
+    worksheet_mit_92 = (
+        19.8400, 19.8445, 19.8489, 19.8697, 19.8736, 19.8920,
+        19.8920, 19.8954, 19.8849, 19.8736, 19.8657, 19.8574,
+    )
+    for m, (cascade, ws) in enumerate(zip(
+        inputs.mean_internal_temp_monthly_c, worksheet_mit_92
+    )):
+        assert abs(cascade - ws) < 1e-3, (
+            f"month {m + 1}: cascade={cascade:.4f} vs worksheet={ws:.4f}"
+        )
+
+
 def test_api_0380_mean_internal_temp_matches_worksheet_92_within_1e_3() -> None:
     # Arrange — SAP 10.2 Appendix N3.5 (PDF p.107) replaces Table 9c
     # steps 3-4 for heat-pump packages with PCDB data: each month

domain/sap10_calculator/rdsap/cert_to_inputs.py

@@ -2041,28 +2041,41 @@ def _heat_pump_extended_heating_days_per_month(
     `mean_internal_temperature_monthly` orchestrator falls through to
     the standard SAP heating schedule (bimodal 9-hour day).
 
-    Only the Variable heating-duration case is handled here — per
-    footnote 48 (PDF p.105) "Daily heating durations of 24, 16 and 9
-    hours are retained for legacy purposes" and modern PCDB Table 362
-    records always lodge "V". The fixed "24" / "16" branches would
-    need a different allocation path (Table N4: 365 days at one mode)
-    that the cohort never exercises; deferred until a cert demands it.
+    Per `heating_duration_code` from the PCDB record (SAP 10.2 PDF
+    p.105 line 6099):
+      - "V" (Variable, modern default per footnote 48): Table N5 PSR
+        interpolation + cold-first allocation via
+        `allocate_extended_heating_days_to_months`.
+      - "24": Table N4 N24,9 = 365 — every day operates at 24-hour
+        heating (no off period), so each month's tuple is
+        (days_in_month, 0).
+      - "16": Table N4 N16,9 = 365 — every day unimodal (one 8h off),
+        each month's tuple is (0, days_in_month).
+      - "9" or other: standard 9-hour schedule = no extended heating →
+        return None so the orchestrator's bimodal fallback applies.
     """
     if main is None or main.main_heating_category != 4:
         return None
-    if hp_record is None or hp_record.heating_duration_code != "V":
+    if hp_record is None:
         return None
-    if hp_record.max_output_kw is None or hp_record.max_output_kw <= 0:
-        return None
-    if hlc_annual_avg_w_per_k <= 0:
-        return None
-    psr = (hp_record.max_output_kw * 1000.0) / (
-        hlc_annual_avg_w_per_k * _SAP_DESIGN_HEAT_LOSS_DELTA_T_K
-    )
-    n24, n16 = extended_heating_days_from_psr_variable(psr=psr)
-    return allocate_extended_heating_days_to_months(
-        n24_9_year=n24, n16_9_year=n16,
-    )
+    code = hp_record.heating_duration_code
+    if code == "V":
+        if hp_record.max_output_kw is None or hp_record.max_output_kw <= 0:
+            return None
+        if hlc_annual_avg_w_per_k <= 0:
+            return None
+        psr = (hp_record.max_output_kw * 1000.0) / (
+            hlc_annual_avg_w_per_k * _SAP_DESIGN_HEAT_LOSS_DELTA_T_K
+        )
+        n24, n16 = extended_heating_days_from_psr_variable(psr=psr)
+        return allocate_extended_heating_days_to_months(
+            n24_9_year=n24, n16_9_year=n16,
+        )
+    if code == "24":
+        return tuple((d, 0) for d in _DAYS_IN_MONTH)
+    if code == "16":
+        return tuple((0, d) for d in _DAYS_IN_MONTH)
+    return None
 
 
 def _primary_loss_applies(