Record ADR-0052: electric boiler/CPSU overrides drag category 2 + conservative Group 1 control 🟪

#1444 Parts A+B for codes 191/192, diagnosed on portfolio 796: 30 of the
first 40 live overrides inherit a replaced system's category (6/4/7) —
suppressing HHRSH or billing direct-acting heat as storage.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/adr/0052-electric-boiler-and-cpsu-overrides-drag-category-2-and-conservative-group-1-control.md

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+# Electric boiler and CPSU overrides drag category 2 and the conservative Group 1 control
+
+## Status
+
+accepted
+
+## Context
+
+[ADR-0048](0048-heating-override-forces-category-and-control-defers-fuel-and-meter.md)
+requires a system-replacing heating override to emit a complete companion set
+(category and control archetype-forced, never inherited) and deferred the
+electric boiler / CPSU expansion; [ADR-0050](0050-electric-underfloor-override-drags-category-8-and-conservative-group-7-control.md)
+completed the underfloor half. This ADR completes the electric-boiler half
+(#1444 Parts A+B for codes **191/192** — the archetypes "Direct-acting
+electric", "Electric boiler", "Electric CPSU").
+
+A portfolio-796 scan of the 126 live 191/192 overrides found **30 of the first
+40 in a suppressed or mis-billed state** from inherited companions:
+
+- **Inherited category 6** (replaced community heating — the bulk): the heating
+  generator's `is_heat_network_main` gate reads the dwelling as a heat network,
+  so the **HHRSH bundle is never offered** — only tune-ups. Same class as
+  ADR-0050's evidence property.
+- **Inherited category 4** (replaced heat pump — property 711954): *every*
+  heating bundle suppressed.
+- **Inherited category 7** (replaced storage heaters — property 721912): the
+  SAP 10.2 Table 12a resolver's category-7 branch bills the direct-acting
+  boiler as storage — **100% at the off-peak low rate** — the precise
+  ADR-0048 room-heater mis-billing, resurfaced.
+- Stale controls ride along (community 23xx, storage 2401, room-heater 2603),
+  applying the wrong Table 4e temperature adjustment.
+
+## Decision
+
+The electric-boiler codes (SAP Table 4a **191** direct-acting electric boiler,
+**192** electric CPSU) join the forced-companion branches of
+`main_heating_system_overlay`:
+
+1. **Category 2** ("boiler system with radiators or underfloor heating") in
+   `_category_for` — deterministic from SAP Table 4a; the same category the
+   gas-boiler overlay already stamps. Table 12a billing for these codes is
+   code-keyed (191 → `DIRECT_ACTING_ELECTRIC_BOILER`, 192 → the deliberate
+   Appendix-F fallback), so the category change *removes* stale-category
+   misrouting rather than selecting a new billing row.
+2. **Control 2101** (SAP Table 4e **Group 1**, "no time or thermostatic control
+   of room temperature", **+0.6 °C**) in `_control_for` — the conservative
+   default within the group the category fixes: the largest Group 1
+   mean-internal-temperature adjustment, so an unobserved control is never
+   over-credited (the boiler mirror of storage 2401 / room-heater 2601 /
+   underfloor 2701). This **supersedes the earlier "direct-acting electric
+   drags no control" choice** — code 191 is a wet Group-1 boiler, and leaving
+   the control unset inherits the replaced system's (the ADR-0048 bug class),
+   which is strictly worse than a conservative assumption.
+
+   Deliberate asymmetry with gas boilers: the gas archetypes force **2106**
+   (full modern controls) because they also assume a modern condensing install
+   (ADR-0035, decided with Khalim) — the whole system is modelled modern. The
+   electric-boiler archetypes describe an *existing* system of unknown vintage
+   modelled at code 191/192's intrinsic efficiency, so the conservative
+   default applies.
+
+Fuel (electricity 29, ADR-0045) and meter (192 off-peak Dual via §12; 191
+Single) were already correct and are unchanged. A forced 2101 also makes the
+system tune-up options available (2101 is improvable) — a coherent cheap lever
+for these dwellings.
+
+## Consequences
+
+- The suppressed cohort regains its heating pathway: category 6/4 inheritors
+  become HHRSH-eligible (verified live: 711954 gains the HHRSH option), and
+  category-7 inheritors stop billing direct-acting heat at the all-night low
+  rate (721912).
+- The "incomplete companion set" error log no longer fires for
+  Direct-acting electric / Electric boiler / Electric CPSU. Remaining gap-log
+  archetypes (#1444): heat pumps (Group 2 control), community heating
+  (Group 3 control — interacts with the Table 4c(3) charging factor, needs an
+  accredited worksheet), then the log flips to a raise (Part C).
+- Overrides re-model with a different (usually lower) baseline where a stale
+  category was over-crediting — an accuracy correction, not a regression.
+
+### Alternatives rejected
+
+- **Keep "no control" for direct-acting electric.** Rejected: `None` is not
+  "no control assumed" — by last-wins composition it means *inherit the
+  replaced system's control*, the silent mis-rating ADR-0048 exists to stop.
+- **Force modern controls (2106) like the gas boilers.** Rejected: nothing in
+  the electric-boiler archetype implies a modern install; assuming full
+  controls over-credits every dwelling whose controls were never observed.