diff --git a/domain/epc/property_overlays/main_heating_system_overlay.py b/domain/epc/property_overlays/main_heating_system_overlay.py
index af334f41c..b8c945393 100644
--- a/domain/epc/property_overlays/main_heating_system_overlay.py
+++ b/domain/epc/property_overlays/main_heating_system_overlay.py
@@ -188,6 +188,14 @@ _CONSERVATIVE_HEAT_PUMP_CONTROL = 2201
 _HEAT_NETWORK_CATEGORY = 6
 _HEAT_NETWORK_CODES = frozenset({301, 302, 303, 304})
 _COMMUNITY_BOILER_CODES = frozenset({301, 302, 303})
+# SAP Table 4e Group 3 heat-network control: 2301 ("flat rate charging, no
+# thermostatic control of room temperature") is the conservative default when
+# the landlord named only the scheme. It is never-over-crediting on BOTH axes
+# the control drives: the largest Group 3 temperature adjustment (+0.3 C, tied
+# with 2302) and the worst Table 4c(3) charging factors (space 1.10, DHW 1.05
+# — an unobserved charging arrangement is never assumed usage-linked). The
+# community mirror of storage 2401 / boiler 2101 / heat-pump 2201 (ADR-0053).
+_CONSERVATIVE_HEAT_NETWORK_CONTROL = 2301
 _COMMUNITY_GAS_FUEL = 20
 
 # SAP Table 4c full boiler-control code: programmer + room thermostat + TRVs. The
@@ -318,6 +326,8 @@ def _control_for(code: int) -> Optional[int]:
         return _CONSERVATIVE_BOILER_CONTROL
     if code in _WET_HEAT_PUMP_CODES:
         return _CONSERVATIVE_HEAT_PUMP_CONTROL
+    if code in _HEAT_NETWORK_CODES:
+        return _CONSERVATIVE_HEAT_NETWORK_CONTROL
     return None
 
 
diff --git a/tests/domain/epc/test_main_heating_system_overlay.py b/tests/domain/epc/test_main_heating_system_overlay.py
index c092c5114..fb856b75c 100644
--- a/tests/domain/epc/test_main_heating_system_overlay.py
+++ b/tests/domain/epc/test_main_heating_system_overlay.py
@@ -94,18 +94,24 @@ def test_electric_room_heaters_overlay_the_room_heater_charge_control() -> None:
 
 def test_overlay_logs_when_it_cannot_complete_a_companion_set(
     caplog: pytest.LogCaptureFixture,
+    monkeypatch: pytest.MonkeyPatch,
 ) -> None:
-    # An archetype the overlay cannot yet fully companion — here community
-    # heating, whose Table 4e Group 3 conservative control is not yet mapped —
-    # is still overlaid (log-and-continue), but the incomplete companion set is
-    # logged as an error so the known gap is visible (CloudWatch) rather than
-    # silently inheriting the replaced system's stale value.
+    # Every real archetype now resolves a complete companion set (ADR-0053),
+    # so the incomplete case is simulated: a hypothetical warm-air heat-pump
+    # archetype (SAP 521 — category 4 but its Table 4e Group 5 control is
+    # deliberately unmapped). The overlay still applies (log-and-continue),
+    # but the incomplete companion set is reported rather than silently
+    # inheriting the replaced system's stale value.
+    from domain.epc.property_overlays import main_heating_system_overlay as mod
+
+    monkeypatch.setitem(mod._MAIN_HEATING_CODES, "Warm-air heat pump", 521)
+
     # Act
     with caplog.at_level(logging.ERROR):
-        main_heating_overlay_for("Community heating, boilers", 0)
+        main_heating_overlay_for("Warm-air heat pump", 0)
 
     # Assert — the gap is reported and names the archetype.
-    assert "Community heating, boilers" in caplog.text
+    assert "Warm-air heat pump" in caplog.text
 
 
 @pytest.mark.parametrize(