Resolve a high-heat-retention storage override to SAP code 409 🟥

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/adr/0044-hhrsh-baseline-archetype-drags-its-intrinsic-controls.md

@@ -0,0 +1,94 @@
+# A baseline HHRSH override drags its intrinsic SAP-409 controls, not the generic manual storage default
+
+## Status
+
+accepted
+
+## Context
+
+A **Landlord Override** naming *"High heat retention storage heaters"* (HHRSH) had
+no home in the heating taxonomy: `MainHeatingSystemType` carried
+`ELECTRIC_STORAGE_OLD` (SAP 401), `_SLIMLINE` (402), `_CONVECTOR` (403) and
+`_FAN` (404), but no High-Heat-Retention member. So the LLM classifier funnelled
+the **best modern storage** into **`"Electric storage heaters, old"` (401)** — the
+**worst** large-volume type. An audit found **111** `property_overrides` rows on
+that mapping (`'Electric Storage Systems: High heat retention storage heaters'` →
+`'Electric storage heaters, old'`). Same missing-archetype defect as ADR-0041.
+
+HHRSH is a distinct, modellable RdSAP system: **SAP Table 4a code 409** (high heat
+retention storage heaters), which the calculator already scores
+(`sap_efficiencies` carries `409: 1.00`). The **HHRSH *measure*** already installs
+this exact code (`_HHR_STORAGE_SAP_CODE = 409`,
+`domain/modelling/generators/heating_recommendation.py`) on a **Dual** off-peak
+meter with **control 2404**.
+
+The subtlety is the **charge control**. `main_heating_system_overlay._control_for`
+drags the **conservative manual** charge control (`2401`) for *every* storage code
+401–409, following ADR-0041's amendment ("an *unobserved* storage charge control
+defaults to the conservative manual one"). Table 4e Group 4's mean-internal-
+temperature adjustments are **manual +0.7 °C, automatic/Celect +0.4 °C, HHR 0 °C**
+— so a manual default carries a penalty. Applying it to a 409 heater would swap
+"scored as old-storage 401" for "scored as 409-but-penalised" — still under-
+crediting the 111 dwellings, and pairing 409 with manual control is not a
+combination RdSAP produces.
+
+**HHRSH has a single, intrinsic charge control (2404).** The control is therefore
+*named by the archetype*, not *unobserved* — unlike a generic storage heater whose
+control genuinely is unknown. So ADR-0041's manual-default rule does not apply to
+409.
+
+## Decision
+
+Add the baseline HHRSH archetype and let it drag its **coherent, intrinsic**
+companions — mirroring how a gas-boiler archetype drags full modern controls
+(`_control_for`) rather than a conservative default.
+
+1. **`MainHeatingSystemType.ELECTRIC_STORAGE_HIGH_HEAT_RETENTION` =
+   `"Electric storage heaters, high heat retention"`**, mapped in
+   `_MAIN_HEATING_CODES` to **SAP Table 4a code 409**.
+2. **Control 2404 (HHRSH controls), not the manual default.** `_control_for`
+   special-cases 409 → `2404` ahead of the generic storage → `2401`. HHRSH's single
+   intrinsic control is archetype-implied, an **exception to ADR-0041's
+   unobserved-storage manual default** (which stands for 401–404).
+3. **Electricity fuel (RdSAP 29).** `_natural_fuel_for` drags electricity for 409,
+   per ADR-0041's "storage → electricity" — so a mis-lodged non-electric fuel can't
+   leave an electric-storage dwelling incoherent. Scoped to 409 ("scoped per family
+   as archetypes land"); the pre-existing 401–404 fuel-drag gap is not touched here.
+4. **Dual/off-peak meter falls out of the code** — 409 is already in
+   `_ASSUMED_DUAL_METER_CODES`, so the off-peak meter drags automatically (ADR-0035
+   coherent companions).
+5. **Deterministic guard + reclassify, TEXT-first / pgEnum-deferred.** A
+   `main_heating_guard` recognises the structured `"Electric Storage Systems: High
+   heat retention storage heaters"` phrasing (wired via `GuardedColumnClassifier`);
+   `scripts/reclassify_hhrsh_storage.py` reuses the same guard as its decision
+   function, updates `property_overrides.override_value` (TEXT) unconditionally, and
+   defers the `landlord_main_heating_system_overrides.value` pgEnum-cache write for
+   the new value.
+
+## Consequences
+
+- The 111 HHRSH dwellings score as **409 + HHR control 2404 + off-peak meter +
+  electricity** — the efficient modern archetype — instead of the worst old
+  large-volume 401. Correct Rebaselining (ADR-0039).
+- **FE-owned pgEnum addition (Dan):** one new `main_heating_system` value,
+  `"Electric storage heaters, high heat retention"` (memory
+  `main-heating-system-pgenum-is-fe-owned`). TEXT read path is fixed on merge; the
+  cache write defers until the migration lands.
+- **Baseline vs measure stay distinct but consistent:** both use code 409 +
+  control 2404; the measure additionally installs a designed HW cylinder / immersion
+  end-state, which a baseline (existing-system) override does not.
+- Extends [ADR-0041](0041-landlord-heating-classification-targets-a-complete-modellable-taxonomy.md)
+  (complete taxonomy; **refines** its manual-default amendment for the single-
+  control HHRSH case) and [ADR-0035](0035-coherent-heating-system-synthesis.md)
+  (companions drag from the code).
+
+### Alternatives rejected
+
+- **409 + manual control (2401), holding to ADR-0041's default.** Rejected: HHRSH's
+  control is intrinsic (single option), not unobserved; the +0.7 °C manual penalty
+  under-credits, and 409+manual is not a real RdSAP combination.
+- **Reuse an existing storage archetype (401–404).** Rejected: none carries the
+  HHR retention/control — the whole point of the mis-score.
+- **Leave fuel unresolved (as 401–404 do).** Rejected for 409: an explicit
+  electricity drag keeps the system coherent if the lodged fuel is wrong; the older
+  archetypes' gap is a separate, out-of-scope cleanup.

tests/domain/epc/test_main_heating_system_overlay.py

@@ -98,6 +98,19 @@ def test_storage_heater_subtypes_decode_to_their_codes(
     assert simulation.heating.sap_main_heating_code == code
 
 
+def test_high_heat_retention_storage_decodes_to_its_own_code_not_old_storage() -> None:
+    # Act
+    simulation = main_heating_overlay_for(
+        "Electric storage heaters, high heat retention", 0
+    )
+
+    # Assert — HHRSH is SAP Table 4a code 409, NOT old large-volume storage (401)
+    # the classifier funnelled it into (ADR-0044).
+    assert simulation is not None
+    assert simulation.heating is not None
+    assert simulation.heating.sap_main_heating_code == 409
+
+
 @pytest.mark.parametrize(
     "main_heating_value",
     [