diff --git a/tests/domain/epc/test_main_heating_system_overlay.py b/tests/domain/epc/test_main_heating_system_overlay.py
index 795a9defe..c092c5114 100644
--- a/tests/domain/epc/test_main_heating_system_overlay.py
+++ b/tests/domain/epc/test_main_heating_system_overlay.py
@@ -108,6 +108,30 @@ def test_overlay_logs_when_it_cannot_complete_a_companion_set(
     assert "Community heating, boilers" in caplog.text
 
 
+@pytest.mark.parametrize(
+    "main_heating_value",
+    ["Community heating, boilers", "Community heating, CHP and boilers"],
+)
+def test_community_heating_drags_the_conservative_group_3_control(
+    main_heating_value: str,
+) -> None:
+    # The landlord names the scheme, not its control or charging arrangement.
+    # The conservative Table 4e Group 3 default is 2301 ("flat rate charging,
+    # no thermostatic control of room temperature"): the largest Group 3
+    # temperature adjustment (+0.3 C) AND the worst Table 4c(3) charging
+    # factors (space 1.10, DHW 1.05) — an unobserved control is never
+    # over-credited and an unobserved charging arrangement is never assumed
+    # usage-linked (ADR-0053). Leaving it unset inherits the replaced system's
+    # control instead (the ADR-0048 bug class).
+    # Act
+    simulation = main_heating_overlay_for(main_heating_value, 0)
+
+    # Assert — SAP Table 4e Group 3 conservative heat-network control.
+    assert simulation is not None
+    assert simulation.heating is not None
+    assert simulation.heating.main_heating_control == 2301
+
+
 def test_air_source_heat_pump_drags_the_conservative_group_2_control() -> None:
     # The landlord names the system, not its control, so the overlay assumes
     # the conservative Table 4e Group 2 default: 2201 ("no time or thermostatic