KNX Power Backup Supervision: Monitoring UPS, Generator and Battery State in ETS6
KNX supervision of power backup infrastructure transforms isolated alarms into a coordinated building response — activating emergency lighting scenes, shedding non-critical loads and escalating alerts to facility management the moment mains power fails or battery reserves run low.
Why KNX supervision for power backup
Without KNX integration, a UPS mains failure or low-battery condition is signalled only by a front-panel LED or local buzzer — invisible to the building management system and to occupants in remote areas of the building. KNX supervision connects these status signals to the entire building automation layer, enabling automatic and recorded responses.
Automatic responses enabled by KNX
- Emergency lighting scene activation on mains fail
- HVAC and EV charger load shedding to extend autonomy
- Occupant notification via Gira X1 popup or room display
- Energy manager integration for battery state awareness
Recorded data for O&M
- Timestamp of each mains fail and restoration event
- Battery SOC at start and end of each event
- Duration of each outage for insurance and compliance
- Generator hours counter for service interval tracking
KNX binary inputs for power status contacts
The simplest and most reliable KNX power supervision uses potential-free relay contacts from the UPS and ATS wired to KNX binary input modules. This method works with any UPS or generator brand that provides auxiliary contacts — no gateway or protocol conversion needed.
Binary input wiring and ETS6 configuration
Input 1 — UPS mains fail: Source: UPS relay output (NC contact — closes on mains fail) KNX device: MDT BE-08230.02 or Siemens 5WG1-125 binary input ETS6 parameter: "Normal position = OPEN" → sends 1 on closure Group address: 8/0/0 — UPS Mains Fail DPT: 1.005 (alarm) — 1 = mains failed, 0 = mains OK Cyclical sending: every 10 minutes (heartbeat for monitoring) Input 2 — Generator running: Source: ATS K2 contactor NO auxiliary (closes when on generator) Group address: 8/0/1 — Generator Running DPT: 1.001 (switch) — 1 = load on generator Reaction time: 10 ms (immediate — no filter delay needed) Input 3 — Battery low: Source: UPS battery low relay (NO — closes at battery < 20%) Group address: 8/0/2 — Battery Low Alarm DPT: 1.005 (alarm) — 1 = battery below threshold Action: immediate load shedding + alarm escalation Input 4 — Battery fault: Source: UPS fault relay (NO — closes on internal fault) Group address: 8/0/3 — UPS Fault DPT: 1.005 (alarm) — triggers maintenance notification
Contact wiring note: use shielded cable for UPS relay contacts to KNX binary input — unshielded cable running alongside power cables in the same duct can pick up switching transients that register as false mains-fail alarms. Connect cable shield to earth at one end only (binary input end) to avoid earth loops.
Modbus TCP UPS to KNX: Eaton gateway integration
IP-enabled UPS units from Eaton, APC and Riello expose battery state, remaining runtime and alarm data via Modbus TCP or SNMP. A KNX Modbus gateway polls these values and publishes them as KNX group addresses, enabling the building automation system to make decisions based on actual battery percentage rather than a simple low-battery threshold.
Eaton UPS Modbus TCP to KNX group address mapping
Eaton 5PX / 9PX with Network Management Card (NMC):
Modbus TCP port: 502, unit ID: 1
Key Modbus registers → KNX group addresses:
Register 0x0020 → Battery capacity (%)
DPT 5.001 → GA 8/1/0 — UPS Battery SOC %
Action: if < 30% → activate Stage 1 load shedding
Register 0x0021 → Estimated remaining runtime (minutes)
DPT 7.001 → GA 8/1/1 — UPS Runtime Remaining min
Action: if < 10 min → activate Stage 2 load shedding
Register 0x0024 → UPS status word (bitmask)
DPT 7.001 → GA 8/1/2 — UPS Status Word
Bit 3 = 1: on battery (mains fail)
Bit 4 = 1: low battery
Bit 5 = 1: fault condition
Register 0x002F → Input voltage L1 (V × 10)
DPT 9.020 → GA 8/1/3 — Mains Voltage V
KNX Modbus gateway options:
Intesis IN701KNX002000 (Modbus TCP master)
MDT KNX/Modbus Gateway (SCN-MBTCP.02)
WAGO 750-362 with KNX couplerETS6 logic: emergency lighting and load shedding
The ETS6 logic module (or an external logic controller such as MDT SCN-LOGM.01) processes the power status group addresses and triggers proportional responses based on the severity of the power event — distinguishing between a brief mains dip, sustained generator operation and a critical low-battery condition.
ETS6 logic module: power event response tree
Condition 1: GA 8/0/0 (Mains Fail) = 1
Delay: 5 seconds (ride-through momentary events)
→ Activate scene 10 "Emergency" on all lighting groups
(dim non-critical areas to 20%, maintain escape routes at 100%)
→ Send value 0 to HVAC temperature setback GA (raise setpoint 4°C)
→ Send OFF to EV charger group address (shed ~7kW)
→ Send OFF to commercial refrigeration pre-cool group
→ Write event timestamp to GA 8/3/0 (Last Mains Fail Time)
Condition 2: GA 8/1/0 (Battery SOC) < 30%
→ Additionally shed: server room AC (transfer to local UPS cooling)
→ Notify Gira X1: popup "Battery below 30% — 30 min autonomy"
→ Send alarm to KNX IP router syslog
Condition 3: GA 8/1/1 (Runtime Remaining) < 10 minutes
→ Initiate graceful shutdown sequence for IT servers
→ Activate Stage 2 load shedding: all non-life-safety loads OFF
→ Priority: emergency lighting, fire alarm, security — maintained
Condition 4: GA 8/0/0 = 0 (mains restored)
→ Delay 90 seconds (allow retransfer and stabilisation)
→ Restore normal lighting scenes (staggered 10-second delays)
→ Restore HVAC setpoints (5-minute delay to limit inrush)
→ EV charger: restore after 3 minutes
→ Log restoration event with durationKNX visualisation: Gira X1 and HomeServer dashboard
A dedicated power backup dashboard on the Gira X1 or HomeServer provides facility managers with at-a-glance status of all backup power assets, historical outage data and battery state trends. The dashboard is configured in Gira Project Assistant (GPA) using standard widget types linked to the group addresses defined above.
Gira X1 power backup dashboard layout
Dashboard page: "Power Backup Status" Row 1 — Status tiles (traffic light widgets): UPS Status: GA 8/0/0 — green=OK, red=Mains Fail Generator: GA 8/0/1 — grey=standby, green=running Battery Low: GA 8/0/2 — green=OK, amber=low, red=critical UPS Fault: GA 8/0/3 — green=OK, red=fault Row 2 — Bargraph widgets: Battery SOC %: GA 8/1/0 — 0–100%, threshold markers at 30% and 80% Mains Voltage: GA 8/1/3 — 0–260V, limit lines at 207V and 253V Row 3 — Numeric displays: Runtime remaining: GA 8/1/1 — minutes, unit label "min" Generator hours: GA 8/4/0 — accumulated counter, unit "h" Row 4 — Event log widget: Last mains fail: GA 8/3/0 — timestamp (DPT 19.001) Last restoration: GA 8/3/1 — timestamp Last outage duration: GA 8/3/2 — minutes
Victron Cerbo GX and KNX integration
Buildings with Victron Energy battery systems — MultiPlus, Quattro or EasySolar inverter-chargers with a Cerbo GX monitoring unit — can integrate battery state of charge and solar power data into the KNX bus via a Modbus TCP bridge. Victron natively exposes all device data on Modbus TCP port 502 without additional licenses.
Victron Cerbo GX Modbus TCP to KNX
Cerbo GX Modbus TCP setup:
Enable in Cerbo GX: Settings > Services > Modbus-TCP: ON
Default port: 502, static IP recommended
Key Modbus registers (unit ID 100 = system overview):
Register 840 → Battery SOC (%) → GA 8/5/0 DPT 5.001
Register 842 → Battery voltage (V×100) → GA 8/5/1 DPT 9.020
Register 843 → Battery power (W) → GA 8/5/2 DPT 13.010
Register 850 → Grid power (W) → GA 8/5/3 DPT 13.010
Register 855 → AC input status → GA 8/5/4 DPT 1.001
0 = disconnected, 1 = connected, 2 = ignore
Bridge options:
Option A: KNX Modbus gateway (Intesis IN701KNX)
→ direct Modbus TCP polling, no middleware
Option B: Node-RED on local server
→ node-red-contrib-victron (official Victron nodes)
→ node-red-contrib-knx (KNX/IP bridge)
→ Adds calculated values: self-consumption %, import cost
KNX action — battery SOC < 20% (GA 8/5/0):
→ Reduce EV charger to minimum 6A
→ Notify visualisation: "Battery low — grid backup active"Cerbo GX to KNX without gateway: if a KNX IP router is accessible on the same LAN, Node-RED running on a Raspberry Pi co-located with the Cerbo GX provides the most flexible bridge. The node-red-contrib-knx library handles KNX/IP tunnelling natively, eliminating the cost of a dedicated Modbus-KNX gateway for battery-only installations.
Alarm escalation: BACnet, SCADA and SMS gateway
For critical facilities — hospitals, data centres, large commercial buildings — power alarm escalation must reach facility management teams within seconds of a mains failure, regardless of time of day. The escalation chain moves from KNX through BACnet or SCADA to SMS, email or pager notification.
Alarm escalation chain
Level 1 — KNX (immediate, building-wide):
GA 8/0/0 = 1 → Emergency lighting + load shedding scenes
KNX visualisation popup on all Gira X1 / touchpanel devices
Reaction time: < 1 second
Level 2 — BACnet alarm (< 10 seconds):
KNX/BACnet gateway (e.g. Intesis IN701BAC) publishes:
BACnet Binary Value: UPS_Mains_Fail (instance 100)
BACnet Analog Value: Battery_SOC (instance 101)
BACnet BBMD broadcasts to building SCADA system
SCADA: alarm acknowledged by operator → work order created
Level 3 — SMS/Email gateway (< 30 seconds):
SCADA → SMS gateway (e.g. SMSEagle, Moxa OnCell) on mains fail
Recipient group: FM engineer on-call, building manager
Message: "MAINS FAIL [building name] [timestamp]
Generator running: [YES/NO]
Battery SOC: [%], Runtime: [min]"
Escalation: if not acknowledged in 5 min → page duty manager
Level 4 — Restoration notification:
GA 8/0/0 = 0 → SMS: "MAINS RESTORED [building] [timestamp]
Outage duration: [X] min"
Auto-close SCADA alarm with duration loggedHospital and data centre requirement: HTM 06-01 (UK hospital electrical infrastructure) and EN 50171 (central power supply for safety lighting) require logged records of every mains failure event with duration, load status and battery autonomy demonstrated. The KNX group address event log combined with the SCADA alarm journal satisfies this requirement — configure both systems to retain a minimum 12-month history.
Need a KNX panel with full power backup supervision and ETS6 logic configured to spec?
We design panels with UPS Modbus integration, KNX binary inputs for generator and battery status, Gira X1 dashboard configuration and BACnet alarm escalation — commissioned and documented for critical facility requirements.
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