Model/domain/sap10_calculator/docs/HANDOVER_POST_S0380_145.md

Handover — post Slices S0380.141..145

Branch: feature/per-cert-mapper-validation. HEAD b1478cff. Predecessor: HANDOVER_POST_S0380_143.md.

TL;DR

Five slices landed on top of 8ee877e4 this session, all driven by the user clarification "target is ΔSAP_c = 0 vs worksheet at 1e-4, not 0.5". Cumulative impact closed pcdb 1 from SAP +6.95 → +0.57 (via S0380.141..143) and closed the electric storage cluster (e3/e6/e7/e2) to <0.21 SAP each (via S0380.145).

Slice	Commit	Scope
S0380.141	6636f1c3	SAP 10.2 §9.4.11 -5pp boiler-interlock applied to BOTH SH eff AND PCDB Eq D1 (was DHW scalar only).
S0380.142	7f9074fc	SAP 10.2 §4 line 7702 + Table 3 cylinder-presence gates: combi_loss=0 when cylinder lodged + primary_loss applies for PCDB Table 322 boilers. Golden cert 0390 re-pinned.
S0380.143	eda6f449	RdSAP 10 §10.11 Table 29 (p.56) — inaccessible-cylinder insulation defaults: age G/H → 25mm foam, I-M → 38mm foam, A-F → loose-jacket strict-raise.
S0380.144	ec6661cb	SAP 10.2 Table 11 — per-Table-4a-code dispatch for electric storage sec_frac (401/402/403/405/406 → 0.15, 404/407 → 0.10). Remove 408 from _FORCE_SECONDARY_FOR_MAIN_CODES per §A.2.2. Cost-invariant for off-peak certs (legacy scalar path billing main and secondary at same rate).
S0380.145	b1478cff	SAP 10.2 Table 4e (p.170-173) "Temperature adjustment, °C" applied to (92)m → (93)m per Table 9c step 8. 52-entry dispatch dict covering all 8 control groups. Closes e3 +2.55→-0.09, e6 +1.33→-0.17, e7 +1.29→-0.20, e2 +0.47→-0.18. e5 regressed +0.07→-1.43 (was net-zero from offsetting bugs).

Extended handover suite at HEAD: 888 pass, 0 fail.

Current residual state at HEAD b1478cff

Cascade-OK tier (25 variants on pin grid) — sorted by |ΔSAP_c|

Variant	SAP code	ΔSAP_c	Δcost	ΔPE	Notes
solid fuel 6	160	+0.03	-£0.65	+45
electric 1	191	-0.06	+£1.32	+94
solid fuel 8	160	-0.08	+£1.85	+45
electric 3	401	-0.09	+£2.01	+82	closed via S0380.145
solid fuel 7	160	+0.10	-£2.33	+17
electric 9	421	-0.12	+£2.72	+91
solid fuel 10	634	-0.16	+£3.70	+67
solid fuel 5	153	-0.17	+£3.81	+93
electric 6	404	-0.17	+£3.91	+103	closed via S0380.145
electric 2	524	-0.18	+£4.24	+393	closed via S0380.145; PE outlier remains
solid fuel 9	636	-0.20	+£4.51	+93
electric 7	408	-0.20	+£4.71	+113	closed via S0380.145
ashp	—	+0.24	-£5.57	-12	(closed)
solid fuel 11	634	-0.26	+£6.07	+104
electric 8	409	-0.26	+£5.92	+126
solid fuel 4	633	-0.29	+£6.73	+90
oil pcdb 1/2	(PCDB)	+0.42	-£9.77	-84	(closed)
pcdb 1	(PCDB oil)	+0.57	-£12.55	-109	closed via S0380.141..143
gshp	—	+1.15	-£26.48	-455	open
oil pcdb 3	(PCDB)	+1.16	-£26.72	-271	open
solid fuel 3	160	+1.32	-£30.45	-935	PE outlier
electric 5	402	-1.43	+£32.85	+535	regressed by S0380.145
solid fuel 2	158	+2.64	-£60.79	-1211	PE outlier
oil 1	(Table 4b)	+2.66	-£61.24	-1050	open: non-PCDB oil HW eff

Σ |ΔSAP_c| across 25 variants ≈ 12.2 SAP points (was 18.0 pre- session, -32% progress).

Blocked tier (16 variants — MissingMainFuelType)

Unchanged from previous handover. Categories: community heating × 5, electric storage 11-14, no system, oil 2-6, pcdb 3.

Next-slice candidates ranked by leverage

1. oil 1 SAP +2.66 / cost -£61 / PE -1050 — biggest open variant

Table 4b oil boiler (code 127, eff 84%) with cylinder lodged + Boiler Interlock=Yes per cert. The §9.4.11 -5pp interlock fix from S0380.141 doesn't apply (interlock present).

Cascade HW kWh 2785 vs worksheet 3639. Worksheet effective HW efficiency ≈ 65% suggests:

• Summer/winter blend the cascade isn't applying for non-PCDB oil boilers per SAP 10.2 Appendix D §D2.1
• Or a Table 4b row that lodges separate HW efficiency

Probe needed before implementing. Spec target: SAP 10.2 Appendix D or Table 4b HW eff row.

2. electric 5 SAP -1.43 — regressed by S0380.145

Pre-S0380.145 was +0.07 (close to zero from offsetting bugs: cascade SH was under by 236 kWh, missing the +0.4 K Table 4e adjustment that would have added ~484 kWh). Post-slice with +0.4 K applied: cascade now OVER worksheet by ~248 kWh.

Root cause: there's a residual cascade-SH OVER-count for electric 5 specifically that S0380.145 exposed. Likely §9 MIT calc for fan-assisted storage heater R=0.40 (Table 4a code 402) OR Table 9b Tsc formula divergence for the specific (R, control_type) pair.

3. solid fuel 2 (+2.64) / 3 (+1.32) PE -935..-1211 — anthracite outliers

Both Table 4a codes 158/160. Distinct cause from oil 1 (no PCDB, solid fuel). Per-variant probe required. Likely Table 4b solid-fuel efficiency row, Table 4f auxiliary energy, or §9 anthracite-specific secondary fraction.

4. gshp +1.15, oil pcdb 3 +1.16 — mid-tier

Each needs its own probe. gshp is heat-pump PCDB Table 362 dispatch; oil pcdb 3 is gas/oil PCDB Table 322 with different boiler model.

5. community heating unblocking (5 variants) — sizable

Extend extractor to capture §14.1 Community Heating block (heat-network codes 41-58). Each cert maps to a Table 32 heat-network code via the lodged heat source type.

6. Electric storage unblocking (variants 11-14) — small

Extend _ELMHURST_MAIN_HEATING_EES_TO_FUEL_CODE for EES codes WEA, REA, OEA.

Important diagnostic findings from this session

1. The "+2.5 SAP cluster" was heterogeneous, NOT a single shared cause. Per-variant probing was essential. The Table 4e fix (S0380.145) closed electric 3/6/7 to <0.21 SAP each; oil 1 + solid fuel 2 remain open with separate drivers.

2. Off-peak electric certs route through _ZERO_FUEL_COST_FOR_OFF_ PEAK sentinel + legacy scalar cost math. Main and secondary are billed at the SAME off-peak low rate (7.41 p/kWh), so changes to sec_frac don't affect cost / SAP for these certs. Only CO2 / PE shift. Discovered while implementing S0380.144.

3. Coincidence-zero closures are NOT real closures. electric 5 was +0.07 pre-S0380.145, which looked like "near-closure". It was actually two opposing bugs canceling. The spec-correct Table 4e fix exposed the underlying SH-demand divergence (-1.43). Per zero-error strict: chase the spec, not the residual sign.

4. Cascade SH demand undercount on electric storage certs was the driver, not Table 11 sec_frac. Table 4e (92)m→(93)m adjustment was the missing spec piece. After S0380.145 the remaining undercount for electric 5 specifically is small enough that overshooting now matters.

Standard slice workflow

1. Read spec page + identify rule
2. Probe one cluster variant; verify diagnosis via monkey-patch
3. Write failing AAA test (literal # Arrange / # Act / # Assert)
4. Implement helper / dispatch entry / mapper extension
5. Re-pin affected variants (DO NOT widen tolerance)
6. Run extended handover suite (command below)
7. Pyright net-zero check (git stash → pyright → git stash pop → pyright)
8. Commit with spec citation + Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
9. Update project-heating-systems-corpus + MEMORY.md index

Test baseline at HEAD b1478cff

PYTHONPATH=/workspaces/model python -m pytest \
    backend/documents_parser/tests/test_summary_pdf_mapper_chain.py \
    backend/documents_parser/tests/test_heating_systems_corpus.py \
    backend/documents_parser/tests/test_elmhurst_extractor.py \
    backend/documents_parser/tests/test_elmhurst_end_to_end.py \
    domain/sap10_calculator/worksheet/tests/test_e2e_elmhurst_sap_score.py \
    domain/sap10_calculator/worksheet/tests/test_heat_transmission.py \
    domain/sap10_calculator/worksheet/tests/test_internal_gains.py \
    domain/sap10_calculator/worksheet/tests/test_solar_gains.py \
    domain/sap10_calculator/worksheet/tests/test_dimensions.py \
    domain/sap10_calculator/worksheet/tests/test_rating.py \
    domain/sap10_calculator/worksheet/tests/test_ventilation.py \
    domain/sap10_calculator/worksheet/tests/test_appendix_h_solar.py \
    domain/sap10_calculator/worksheet/tests/test_mev.py \
    domain/sap10_calculator/rdsap/tests/test_cert_to_inputs.py \
    domain/sap10_calculator/rdsap/tests/test_golden_fixtures.py \
    domain/sap10_calculator/tests/test_pcdb_table_322_lookup.py \
    domain/sap10_calculator/tests/test_pcdb_table_329_lookup.py \
    domain/sap10_calculator/tests/test_table_12a.py \
    --no-cov -q

Expected: 888 pass, 0 fail.

Memories to load (in order)

project-heating-systems-corpus    # HEAD b1478cff
feedback-sap-10-2-only-never-10-3 # CRITICAL — never reference SAP 10.3
feedback-worksheet-not-api-reference
feedback-spec-citation-in-commits
feedback-verify-handover-claims
feedback-zero-error-strict        # TARGET: ΔSAP_c < 1e-4 vs worksheet
feedback-commit-per-slice
feedback-aaa-test-convention
feedback-e2e-validation-philosophy
feedback-abs-diff-over-pytest-approx
feedback-spec-floor-skepticism
feedback-golden-residuals-near-zero
feedback-one-e-minus-4-across-the-board
reference-unmapped-sap-code       # updated S0380.145
reference-unmapped-api-code
project-oil-price-spec-divergence

What NOT to do

• Don't reference SAP 10.3 — track 10.2 deliberately
• Don't widen pin tolerances to make pins pass — re-pin smaller or find the spec gap
• Don't re-investigate Slices .91..145 — all settled
• Don't add new helpers to domain/sap10_ml/ — on deprecation path
• Don't treat ΔSAP=0.07 as "closed" — it might be offsetting bugs. Target is < 1e-4 vs worksheet.
• Don't follow the previous handover's "shared cluster cause" framing — S0380.144/.145 confirmed each of the original +2.5 SAP cluster members has a distinct driver.

Spec source quick-reference

All under domain/sap10_calculator/docs/specs/:

• SAP 10.2 full spec: sap-10-2-full-specification-2025-03-14.pdf
  • §4 (p.135-137) — water heating worksheet (45..65), Tables 2/2a/2b
  • §9 (p.155+) — MIT calc, Tables 9/9a/9b/9c
  • §9.4.11 (p.30) — Boiler interlock: -5pp to BOTH SH and DHW
  • §A.2.2 (~p.189) — Forced-secondary set "401 to 407, 409 and 421"
  • Table 3 (p.160) — Primary circuit loss; zero-loss list
  • Table 4a (p.163-170) — heating systems incl. R column
  • Table 4b — gas/liquid boilers seasonal efficiency
  • Table 4c (p.169-170) — Efficiency adjustments
  • Table 4d (p.170) — heat-emitter R
  • Table 4e (p.170-173) — heating system controls + temperature adjustment column (8 groups)
  • Table 4f (p.174) — pumps + fans
  • Table 9 (p.182) — heating periods and temperatures
  • Table 9c (p.184) — heating requirement (step 8 = apply Table 4e adjustment)
  • Table 11 (p.188) — secondary heating fraction
  • Table 12 (p.191) — SAP rating fuel prices
  • Table 12a (p.191) — high/low-rate fraction by system × tariff
  • Appendix D §D2.1 — PCDB monthly cascade Eq D1
• RdSAP 10 spec: RdSAP 10 Specification 10-06-2025.pdf
  • §10.11 Table 29 (p.56) — Heating and hot water parameters; inaccessible cylinder defaults
  • §19 Table 32 (p.95) — RdSAP10 fuel prices / CO2 / PE

Good luck.