diff --git a/custom_components/localthings/registry/by_type/__init__.py b/custom_components/localthings/registry/by_type/__init__.py
index 4fa49d9..7f6b864 100644
--- a/custom_components/localthings/registry/by_type/__init__.py
+++ b/custom_components/localthings/registry/by_type/__init__.py
@@ -113,6 +113,15 @@ def for_device_by_model(model_num: str, description: str) -> Optional[DeviceRegi
     # 'P' sits between the underscore and 'RAC' in that token).
     if key is None and '_RAC_' in (model_num or ''):
         key = 'airconditioner'
+    # System air conditioners (multi-indoor-unit commercial installs, e.g.
+    # A-CAWW-TP2-20-COMMON, issue #52) report no oneUiVersion either and
+    # carry the '-CAWW-' board-family token instead of '_RAC_'/'_PRAC_'.
+    # Same TP1X/TP2X-class resource surface as the room-AC models above
+    # (confirmed by the issue #52 dump binding cleanly against the existing
+    # airconditioner registry once routed here), plus one new SAC-specific
+    # resource (see airconditioner.py's _AC_IGNORED).
+    if key is None and '-CAWW-' in (model_num or '').upper():
+        key = 'airconditioner'
     # Air purifiers (e.g. ARTIK051_TVTL_18K, issue #56) report no
     # oneUiVersion either, and carry the '_TVTL_' board-family token.
     if key is None and '_TVTL_' in (model_num or ''):
diff --git a/custom_components/localthings/registry/capabilities/airconditioner.py b/custom_components/localthings/registry/capabilities/airconditioner.py
index c58cf03..0137163 100644
--- a/custom_components/localthings/registry/capabilities/airconditioner.py
+++ b/custom_components/localthings/registry/capabilities/airconditioner.py
@@ -243,6 +243,11 @@ _AC_IGNORED = [
     '/remotetemperature/vs/0',     # external temp-sensor feed (unset on this unit)
     '/reserverulesets/vs/0',       # opaque hex-encoded schedule reservation blob
     '/welcome/temperature/vs/0',   # welcome-cooling plumbing
+    # System-AC-only (multi-indoor-unit commercial installs, e.g.
+    # A-CAWW-TP2-20-COMMON, issue #52): opaque hex-encoded installation
+    # topology -- indoor/outdoor unit pairing, per-unit serials, MCU info.
+    # Commissioning-time plumbing, not user-actionable appliance state.
+    '/sac/installationinfo/vs/0',
 ]
 
 # Built as bare no-entity caps; folded into the AC registry (not global).
diff --git a/tests/fixtures/airconditioner_caww_tp2_device.json b/tests/fixtures/airconditioner_caww_tp2_device.json
new file mode 100644
index 0000000..481110a
--- /dev/null
+++ b/tests/fixtures/airconditioner_caww_tp2_device.json
@@ -0,0 +1,486 @@
+{
+  "device0": [
+    {
+      "rt": [
+        "x.com.samsung.devcol",
+        "oic.wk.col"
+      ],
+      "if": [
+        "oic.if.baseline",
+        "oic.if.ll",
+        "oic.if.b"
+      ]
+    },
+    {
+      "href": "/aisleep/vs/0",
+      "rep": {
+        "x.com.samsung.da.displayNightMode": "Off",
+        "x.com.samsung.da.elapsedTime": "0",
+        "x.com.samsung.da.requestFeedback": "Off",
+        "x.com.samsung.da.resultFeedback": "0",
+        "x.com.samsung.da.statusFeedback": "Idle",
+        "x.com.samsung.da.sleepTime": "14002200",
+        "x.com.samsung.da.sleepMode": "Off"
+      }
+    },
+    {
+      "href": "/alarms/vs/0",
+      "rep": {
+        "x.com.samsung.da.items": [
+          {
+            "x.com.samsung.da.id": "0",
+            "x.com.samsung.da.description": "Alarm",
+            "x.com.samsung.da.alarmType": "Device",
+            "x.com.samsung.da.code": "ErrorCode_OFF",
+            "x.com.samsung.da.triggeredTime": "2026-07-23T05:13:21",
+            "x.com.samsung.da.state": "Deleted"
+          },
+          {
+            "x.com.samsung.da.id": "1",
+            "x.com.samsung.da.description": "Alarm",
+            "x.com.samsung.da.alarmType": "Device",
+            "x.com.samsung.da.code": "FilterAlarm_OFF",
+            "x.com.samsung.da.triggeredTime": "2026-07-23T05:13:21",
+            "x.com.samsung.da.state": "Deleted"
+          }
+        ]
+      }
+    },
+    {
+      "href": "/availablecontrolsets/vs/0",
+      "rep": {
+        "x.com.samsung.da.sets": "000100B4012C0000120000000000",
+        "x.com.samsung.da.id": "CAC",
+        "x.com.samsung.da.version": "1.0"
+      }
+    },
+    {
+      "href": "/configuration/vs/0",
+      "rep": {
+        "x.com.samsung.da.region": "4131000000",
+        "x.com.samsung.da.airconOptionList": [
+          "DR",
+          "SingleCommand_1.0",
+          "AI_2.0"
+        ]
+      }
+    },
+    {
+      "href": "/diagnosis/vs/0",
+      "rep": {}
+    },
+    {
+      "href": "/drlc/vs/0",
+      "rep": {
+        "x.com.samsung.da.drlcLevel": "0",
+        "x.com.samsung.da.durationminutes": "0",
+        "x.com.samsung.da.start": "1970-01-01T00:00:00Z",
+        "x.com.samsung.da.override": "Off",
+        "x.com.samsung.da.realSaving": "Off"
+      }
+    },
+    {
+      "href": "/energy/consumption/vs/0",
+      "rep": {
+        "x.com.samsung.da.instantaneousPower": "153.000000",
+        "x.com.samsung.da.cumulativePower": "239209",
+        "x.com.samsung.da.cumulativeSavedPower": "7201",
+        "x.com.samsung.da.cumulativeUnit": "Wh",
+        "x.com.samsung.da.instantaneousPowerUnit": "W",
+        "x.com.samsung.da.cumulativePowerType": "total",
+        "x.com.samsung.da.saveLocation": "/mnt/usage.db"
+      }
+    },
+    {
+      "href": "/file/information/vs/0",
+      "rep": {
+        "x.com.samsung.timeoffset": "+09:00",
+        "x.com.samsung.supprtedtype": 1
+      }
+    },
+    {
+      "href": "/filter/airdustfilter/vs/0",
+      "rep": {
+        "x.com.samsung.da.filterUsage": "85",
+        "x.com.samsung.da.filterUsageResolution": "1",
+        "x.com.samsung.da.filterStatus": "normal",
+        "x.com.samsung.da.filterCapacity": "1000",
+        "x.com.samsung.da.filterCapacityUnit": "Hour",
+        "x.com.samsung.da.filterResetType": [
+          "replaceable",
+          "washable"
+        ]
+      }
+    },
+    {
+      "href": "/humidity/vs/0",
+      "rep": {
+        "x.com.samsung.da.humidity": "0.000000",
+        "x.com.samsung.da.fivepercentHumidity": "83"
+      }
+    },
+    {
+      "href": "/information/vs/0",
+      "rep": {
+        "x.com.samsung.da.modelNum": "A-CAWW-TP2-20-COMMON|10241941|600301170016110B40000F2000F2AD00",
+        "x.com.samsung.da.description": "A-CAWW-TP2-20-COMMON",
+        "x.com.samsung.da.serialNum": "**REDACTED**",
+        "x.com.samsung.da.otnDUID": "**REDACTED**",
+        "x.com.samsung.da.diagProtocolType": "WIFI_HTTPS",
+        "x.com.samsung.da.diagLogType": [
+          "errCode",
+          "dump"
+        ],
+        "x.com.samsung.da.diagDumpType": "file",
+        "x.com.samsung.da.diagEndPoint": "SSM",
+        "x.com.samsung.da.diagMnid": "0AJT",
+        "x.com.samsung.da.diagSetupid": "023",
+        "x.com.samsung.da.diagMinVersion": "1.0",
+        "x.com.samsung.da.items": [
+          {
+            "x.com.samsung.da.id": "0",
+            "x.com.samsung.da.description": "Version",
+            "x.com.samsung.da.type": "Software",
+            "x.com.samsung.da.number": "02274A260512",
+            "x.com.samsung.da.newVersionAvailable": "0"
+          },
+          {
+            "x.com.samsung.da.id": "1",
+            "x.com.samsung.da.description": "Version",
+            "x.com.samsung.da.type": "Firmware",
+            "x.com.samsung.da.number": "02419A25051901,FFFFFFFFFFFFFF",
+            "x.com.samsung.da.newVersionAvailable": "0"
+          },
+          {
+            "x.com.samsung.da.id": "2",
+            "x.com.samsung.da.description": "Version",
+            "x.com.samsung.da.type": "Outdoor",
+            "x.com.samsung.da.number": "FFFFFFFFFFFFFF,FFFFFFFFFFFFFF"
+          }
+        ]
+      }
+    },
+    {
+      "href": "/keepnormalstate/vs/0",
+      "rep": {
+        "x.com.samsung.da.keepnormal": 0
+      }
+    },
+    {
+      "href": "/mode/convenient/vs/0",
+      "rep": {
+        "x.com.samsung.da.modes": "Off",
+        "x.com.samsung.da.supportedModes": [
+          "Off",
+          "Nano",
+          "LongWind",
+          "Speed",
+          "Sleep",
+          "NanoSleep"
+        ]
+      }
+    },
+    {
+      "href": "/mode/vs/0",
+      "rep": {
+        "x.com.samsung.da.workingMode": "Auto",
+        "x.com.samsung.da.supportedModes": [
+          "Auto",
+          "Cool",
+          "Dry",
+          "Fan",
+          "AIComfort"
+        ],
+        "x.com.samsung.da.modes": [
+          "Auto"
+        ],
+        "x.com.samsung.da.options": [
+          "Sleep_0",
+          "ArtificialWorking_Off",
+          "ComfortAICooling_Off",
+          "AiTempChanged_Off",
+          "AiTemp_240",
+          "OutdoorTemp_82",
+          "Light_Off",
+          "Volume_100",
+          "KeyInputPermit_On",
+          "ModePermit_NoLimit",
+          "UpdateAllow_NotAllowed",
+          "DurationOn_419",
+          "WelcomeCoolingState_Off"
+        ]
+      }
+    },
+    {
+      "href": "/option/autoclean/vs/0",
+      "rep": {
+        "x.com.samsung.da.status": "Stop",
+        "x.com.samsung.da.settingStatus": "On",
+        "x.com.samsung.da.progress": "0",
+        "x.com.samsung.da.supportedStatus": [
+          "Start",
+          "Stop"
+        ],
+        "x.com.samsung.da.supportedSettingStatus": [
+          "On",
+          "Off"
+        ]
+      }
+    },
+    {
+      "href": "/option/muteonce/vs/0",
+      "rep": {
+        "muteonce": "Off"
+      }
+    },
+    {
+      "href": "/otninformation/vs/0",
+      "rep": {
+        "x.com.samsung.da.target": "",
+        "x.com.samsung.da.newVersionAvailable": "false",
+        "x.com.samsung.da.newVersionNo": "00000000",
+        "x.com.samsung.da.currentVersionInfo": "00000000",
+        "otnStatus": "None",
+        "flashingProgress": "",
+        "otnTarget": "main",
+        "otnCompleteDate": "noHistory",
+        "otnList": [
+          {
+            "type": "WIFI",
+            "modelId": "A-CAWW-TP2-20-COMMON",
+            "versions": [
+              "14260512"
+            ],
+            "visVersion": "260512"
+          },
+          {
+            "type": "Micom",
+            "modelId": "040010241941FFFFFFFF",
+            "versions": [
+              "25051901",
+              "FFFFFFFF"
+            ],
+            "visVersion": "250519"
+          },
+          {
+            "type": "Micom",
+            "modelId": "0400FFFFFFFFFFFFFFFF",
+            "versions": [
+              "FFFFFFFF",
+              "FFFFFFFF"
+            ],
+            "visVersion": ""
+          }
+        ]
+      }
+    },
+    {
+      "href": "/power/vs/0",
+      "rep": {
+        "x.com.samsung.da.power": "Off"
+      }
+    },
+    {
+      "href": "/realtimenotiforclient/vs/0",
+      "rep": {
+        "x.com.samsung.da.timeforshortnoti": "0",
+        "x.com.samsung.da.longnotisubscription": "true",
+        "x.com.samsung.da.periodicnotisubscription": "true"
+      }
+    },
+    {
+      "href": "/reserverulesets/vs/0",
+      "rep": {
+        "x.com.samsung.da.sets": "1F121E121E121E121EFFFFFFFF010001000F0001000E0000001C",
+        "x.com.samsung.da.id": "CAC",
+        "x.com.samsung.da.version": "1.0"
+      }
+    },
+    {
+      "href": "/sac/installationinfo/vs/0",
+      "rep": {
+        "installationOptions": [
+          {
+            "id": "0",
+            "option": "17444980C80171700010"
+          },
+          {
+            "id": "1",
+            "option": "28010000000000000100"
+          },
+          {
+            "id": "2",
+            "option": "50000000000000000000"
+          },
+          {
+            "id": "3",
+            "option": "30000000000000000000"
+          }
+        ],
+        "installationDeviceNum": [
+          {
+            "id": "0",
+            "number": "01"
+          },
+          {
+            "id": "1",
+            "number": "04"
+          },
+          {
+            "id": "2",
+            "number": "00"
+          }
+        ],
+        "outdoorInfo": [
+          {
+            "id": "0",
+            "info": "01900A230418",
+            "serial": "**REDACTED**"
+          },
+          {
+            "id": "1",
+            "info": "000000000000",
+            "serial": "**REDACTED**"
+          },
+          {
+            "id": "2",
+            "info": "000000000000",
+            "serial": "**REDACTED**"
+          },
+          {
+            "id": "3",
+            "info": "000000000000",
+            "serial": "**REDACTED**"
+          }
+        ],
+        "mcuInfo": [
+          {
+            "id": "0",
+            "info": ""
+          },
+          {
+            "id": "1",
+            "info": ""
+          },
+          {
+            "id": "2",
+            "info": ""
+          },
+          {
+            "id": "3",
+            "info": ""
+          },
+          {
+            "id": "4",
+            "info": ""
+          },
+          {
+            "id": "5",
+            "info": ""
+          },
+          {
+            "id": "6",
+            "info": ""
+          },
+          {
+            "id": "7",
+            "info": ""
+          },
+          {
+            "id": "8",
+            "info": ""
+          },
+          {
+            "id": "9",
+            "info": ""
+          },
+          {
+            "id": "10",
+            "info": ""
+          },
+          {
+            "id": "11",
+            "info": ""
+          },
+          {
+            "id": "12",
+            "info": ""
+          },
+          {
+            "id": "13",
+            "info": ""
+          },
+          {
+            "id": "14",
+            "info": ""
+          },
+          {
+            "id": "15",
+            "info": ""
+          }
+        ]
+      }
+    },
+    {
+      "href": "/temperature/control/vs/0",
+      "rep": {
+        "x.com.samsung.da.increment": "0.5"
+      }
+    },
+    {
+      "href": "/temperatures/vs/0",
+      "rep": {
+        "x.com.samsung.da.items": [
+          {
+            "x.com.samsung.da.id": "0",
+            "x.com.samsung.da.description": "Temperature",
+            "x.com.samsung.da.desired": "27.0",
+            "x.com.samsung.da.current": "29.0",
+            "x.com.samsung.da.maximum": "30",
+            "x.com.samsung.da.minimum": "18",
+            "x.com.samsung.da.increment": "0.5",
+            "x.com.samsung.da.unit": "Celsius"
+          }
+        ]
+      }
+    },
+    {
+      "href": "/timezone/vs/0",
+      "rep": {
+        "timezoneid": "Asia/Seoul",
+        "offset": "+09:00",
+        "DST": "OFF"
+      }
+    },
+    {
+      "href": "/wind/direction/vs/0",
+      "rep": {
+        "x.com.samsung.da.modes": "Fix",
+        "x.com.samsung.da.supportedModes": [
+          "Up_And_Low",
+          "Fix",
+          "Left_And_Right",
+          "All"
+        ]
+      }
+    },
+    {
+      "href": "/wind/strength/vs/0",
+      "rep": {
+        "x.com.samsung.da.modes": "0",
+        "x.com.samsung.da.supportedModes": [
+          "0",
+          "1",
+          "2",
+          "3"
+        ],
+        "x.com.samsung.da.modesName": [
+          "Auto",
+          "Low",
+          "Mid",
+          "High"
+        ]
+      }
+    }
+  ]
+}
diff --git a/tests/fixtures/golden/airconditioner_caww_tp2.json b/tests/fixtures/golden/airconditioner_caww_tp2.json
new file mode 100644
index 0000000..290a269
--- /dev/null
+++ b/tests/fixtures/golden/airconditioner_caww_tp2.json
@@ -0,0 +1,15 @@
+{
+  "state_keys": [
+    "air_filter_status",
+    "air_filter_usage",
+    "alarm_code",
+    "auto_clean",
+    "climate",
+    "diagnosis_status",
+    "energy_kwh",
+    "energy_saved_kwh",
+    "firmware_update",
+    "mute_once",
+    "power_watts"
+  ]
+}
diff --git a/tests/test_airconditioner_capabilities.py b/tests/test_airconditioner_capabilities.py
index 676f026..981dc5d 100644
--- a/tests/test_airconditioner_capabilities.py
+++ b/tests/test_airconditioner_capabilities.py
@@ -215,6 +215,30 @@ def test_tp1x_rac_expected_state_keys_present():
         assert key in state, key
 
 
+def test_caww_tp2_model_resolves_via_model_fallback():
+    """A-CAWW-TP2-20-COMMON (issue #52, System AC) reports no oneUiVersion
+    and no '_RAC_'/'_PRAC_' token -- resolved via the '-CAWW-' modelNum
+    fallback added for this device."""
+    reg, _ = _resolve('airconditioner_caww_tp2')
+    assert reg is not None and reg.name == 'airconditioner'
+
+
+def test_caww_tp2_no_unbound_hrefs():
+    """Every resource in the issue #52 dump binds or is ignored -- clears
+    the coverage-gap repair. Only new href beyond the existing RAC/PRAC
+    surface is /sac/installationinfo/vs/0 (opaque SAC installation topology,
+    ignored)."""
+    reg, resources = _resolve('airconditioner_caww_tp2')
+    unbound = []
+    discover(resources, reg.capabilities, reg.pattern_capabilities, log=unbound.append)
+    assert unbound == []
+
+
+def test_caww_tp2_sac_installationinfo_is_ignored():
+    ignored_hrefs = {cap.href for cap in airconditioner.COVERAGE}
+    assert '/sac/installationinfo/vs/0' in ignored_hrefs
+
+
 def test_mute_once_write_target():
     write = airconditioner.MUTE_ONCE.entities[0].write_fn
     assert write('On', {}) == (['option', 'muteonce', 'vs', '0'], {'muteonce': 'On'})
diff --git a/tests/test_golden_regression.py b/tests/test_golden_regression.py
index e3159cb..56ba878 100644
--- a/tests/test_golden_regression.py
+++ b/tests/test_golden_regression.py
@@ -213,6 +213,24 @@ def test_registry_reproduces_golden_state_keys_for_tp2x_rac_20k():
     )
 
 
+def test_registry_reproduces_golden_state_keys_for_caww_tp2():
+    """A-CAWW-TP2-20-COMMON (issue #52, System AC / multi-indoor-unit
+    commercial install) reports no oneUiVersion and no '_RAC_'/'_PRAC_'
+    token; resolved via the '-CAWW-' modelNum fallback in
+    for_device_by_model. Otherwise binds cleanly against the existing
+    airconditioner registry -- same TP1X/TP2X-class resource surface, plus
+    one SAC-only installation-topology resource (ignored)."""
+    from tests.conftest import _load_device
+    resources = _load_device('airconditioner_caww_tp2')
+    golden = json.loads((GOLDEN / 'airconditioner_caww_tp2.json').read_text())
+    state_keys = _new_state_keys('airconditioner_caww_tp2', resources)
+    assert set(state_keys) == set(golden['state_keys']), (
+        f"state_keys mismatch:\n"
+        f"  extra:   {sorted(set(state_keys) - set(golden['state_keys']))}\n"
+        f"  missing: {sorted(set(golden['state_keys']) - set(state_keys))}"
+    )
+
+
 def test_registry_reproduces_golden_state_keys_for_tp1x_rac():
     """TP1X_DA-AC-RAC-01001_0000 (issue #38) -- fuller RAC board with display
     light, self-check, mute-once, and a current-limit setting."""