Vaillant
German heat pumps and boilers — Modbus TCP integration for KNX energy management and SG Ready smart grid control.
Vaillant Group (Remscheid, Germany — founded 1874) manufactures residential and light commercial heating and cooling systems: aroTHERM plus air-source heat pumps (R290 propane refrigerant, A++ to A+++ energy rating), flexoTHERM ground-source heat pumps, ecoTEC series gas and combi boilers, hybrid heat pump systems, and domestic hot water cylinders (uniSTOR). Across Europe, Vaillant is one of the most-specified heat pump brands for residential renovation and new build — widely used alongside KNX room control systems for zone heating, DHW schedules and energy monitoring. The aroTHERM plus heat pump integrates with KNX via the VWZ AI Modbus TCP/RTU interface adapter, providing read access to flow temperature, return temperature, compressor state, COP and energy counters. SG Ready smart grid inputs on the outdoor unit allow KNX relay outputs to trigger heat pump boost modes for solar surplus and cheap-tariff charging.
Role in our panels
How we use Vaillant
The VWZ AI interface adapter (Article 0020261780) mounts on the aroTHERM plus indoor unit and exposes both Modbus RTU (RS-485) and Modbus TCP (RJ45 Ethernet, port 502, slave address 1). Key readable registers: register 1 (operating mode: 0=standby, 1=heating, 2=DHW, 3=cooling), register 5 (flow temperature setpoint, °C × 10), register 6 (actual flow temperature, °C × 10), register 7 (return temperature, °C × 10), register 10 (COP × 100), register 20 (daily energy consumption, Wh). A KNX-Modbus gateway (Weinzierl KNX ENO 634 or Intesis IBOX-KNX-MBS-100) polls these registers every 60 seconds and updates KNX group addresses — flow temperature as DPT 9.001, COP as DPT 9.002, daily energy as DPT 14.019. SG Ready: the aroTHERM plus outdoor unit has two digital input terminals (SG1 and SG2). Volt-free contacts from KNX relay outputs (MDT SRA relay module or ABB RM/S relay actuator) close these terminals to select operating mode.
KNX panel wiring for Vaillant aroTHERM plus: VWZ AI adapter connects to building LAN via RJ45 — include RJ45 patch panel in the electrical panel for structured cabling. KNX-Modbus gateway on the same LAN segment reads Modbus TCP registers every 60 seconds. SG Ready wiring: KNX relay output (volt-free contact, 24V DC rated minimum — use relay with gold-plated contacts for low-current signals) → 2-core cable to Vaillant outdoor unit SG Ready terminal block. SG1 closed alone = Mode 3 (cheap tariff, raise flow setpoint 3-5°C, DHW boost). SG1 and SG2 both closed = Mode 4 (PV surplus, maximum heating, fill buffer). SG1 open = Mode 2 (normal operation). Important: Vaillant SG Ready expects volt-free contact, not 230V or 24V supply — wire relay output only, no power supply to SG terminals.
Used in these project types
Vaillant products
Key components we install
Vaillant aroTHERM plus 5.5kW ASHP
5.5kW monobloc air-source heat pump with R290 (propane) refrigerant, A++ rating, COP 4.4 at A7/W35. Single-phase 230V AC supply. Modbus TCP via VWZ AI adapter (sold separately). SG Ready 2 digital inputs on outdoor unit (volt-free contacts). For residential heating up to 120m2 with underfloor heating (max flow temp 55°C) or up to 80m2 with radiators (max flow temp 70°C). Quiet mode operation from 35dB(A). Compatible with Vaillant uniSTOR DHW cylinder and hydraulic module. ETS6: KNX group objects for flow temp, COP, operating mode via Weinzierl Modbus gateway.
Vaillant aroTHERM plus 10.5kW ASHP
10.5kW monobloc air-source heat pump, R290 refrigerant, three-phase 400V supply, A+++ at A7/W35. For larger residential (150-250m2) and light commercial buildings with underfloor heating. Same VWZ AI Modbus TCP integration as 5.5kW model — register map identical. Three-phase supply from dedicated MCB in distribution panel (3 × C16A typical). SG Ready 2 inputs operational in all models. Commonly paired with 300L uniSTOR cylinder and Vaillant hydraulic module for buffered underfloor heating system. KNX panel monitors energy per zone via separate KNX heat meters on UFH manifold.
Vaillant flexoTHERM exclusive 18.7kW GSHP
18.7kW ground-source heat pump, three-phase 400V, Modbus TCP via VWZ AI adapter. COP 5.1 at B0/W35 (brine-to-water). For passive houses and high-performance buildings with borehole or horizontal ground loop. Modbus register map identical to aroTHERM plus — same KNX integration path (VWZ AI adapter, KNX-Modbus gateway, same group address DPTs). Higher COP than air-source — KNX energy dashboard shows lower kWh cost per kWh heat output. Three-phase supply requires 3 × C25A MCB, 6mm2 cable. Quiet operation (no outdoor fan) — suitable for noise-sensitive sites.
Vaillant ecoTEC plus Combi Boiler
28kW ErP A-rated gas combi boiler with OpenTherm connectivity. Used as backup heat source in hybrid heat pump systems alongside aroTHERM plus. OpenTherm connection to Vaillant openTHERM controller or direct to HA OpenTherm gateway (OTGW) for setpoint control from HA. In hybrid system: KNX outdoor temperature sensor triggers mode switch — below -5°C ambient, KNX relay activates ecoTEC gas boiler and signals aroTHERM to standby mode (via Modbus write to register 1). Above 0°C, KNX reverses: heat pump primary, boiler standby. Dual-fuel setup requires BS EN 14511 compliance documentation.
Vaillant VWZ AI Modbus Interface Adapter
Modbus TCP and Modbus RTU interface adapter for aroTHERM plus and flexoTHERM series. Article number 0020261780. Mounts on indoor unit, connects to Vaillant eBUS system internally. Exposes RJ45 Ethernet (Modbus TCP, port 502, slave address 1 default) and RS-485 terminals (Modbus RTU). Register list available from Vaillant technical support portal (login required). KNX integration: VWZ AI on LAN → KNX-Modbus gateway (Weinzierl KNX ENO 634 or Intesis IBOX-KNX-MBS) polls every 60s → KNX group addresses updated for visualisation. Mandatory accessory for any KNX-Vaillant heat pump project.
Vaillant FAQ
How does Vaillant aroTHERM plus connect to KNX via Modbus?
Install the VWZ AI interface adapter (article 0020261780) on the aroTHERM plus indoor unit — it connects to the eBUS communication bus internally and exposes Modbus TCP on RJ45 (port 502, slave address 1). Key holding registers: register 1 = operating mode (0=standby, 1=heating, 2=DHW, 3=cooling), register 5 = flow temperature setpoint (°C × 10), register 6 = actual flow temperature (°C × 10), register 7 = return temperature (°C × 10), register 10 = COP (× 100, so value 440 = COP 4.4), register 20 = daily energy consumption (Wh). A KNX-Modbus gateway (Weinzierl KNX ENO 634 recommended) polls every 60 seconds and pushes values to KNX group addresses. KNX DPTs: flow temperature as 9.001 (2-byte float), COP as 9.002, daily energy as 14.019 (4-byte float kWh). Register writes are supported for setpoint (register 5) and mode (register 1), but direct KNX writes to heat pump mode should only be used with proper logic to avoid short-cycling.
What is SG Ready and how does KNX control it?
SG Ready (Smart Grid Ready) is a German VDE standard defining four operating modes for heat pumps: Mode 1 = hard block (grid operator emergency signal — heat pump off), Mode 2 = normal operation (no SG signal), Mode 3 = cheap tariff or reduced grid load (raise flow setpoint by 3-5°C, enable DHW boost — lower the effective electricity cost), Mode 4 = PV surplus maximum (maximum heating, fill buffer tank, charge DHW cylinder to maximum setpoint). The two SG Ready digital input terminals on the Vaillant outdoor unit accept volt-free contacts only — never apply voltage directly. KNX relay output wiring: Mode 2 = both contacts open (normal). Mode 3 = SG contact 1 closed (KNX relay 1 energised). Mode 4 = both SG contacts closed (KNX relay 1 and relay 2 both energised). Mode 1 block = external block input closed (separate terminal on outdoor unit). KNX solar logic: Fronius inverter surplus power (Modbus TCP) above 2.0kW sustained for 5 minutes → HA sets KNX group address → KNX relay actuator (MDT SRA-0800.01) closes SG contact 2 for Mode 4. Cheap-tariff schedule: ETS6 time object drives KNX relay to Mode 3 during off-peak hours.
Can Vaillant heat pumps integrate with BACnet for commercial projects?
Vaillant does not natively support BACnet — Modbus TCP (via VWZ AI adapter) is the only digital integration protocol on the aroTHERM plus and flexoTHERM series. For commercial projects where the BMS uses BACnet (Honeywell Niagara JACE, Siemens Desigo CC, Schneider EcoStruxure), use an HMS Anybus Communicator gateway to translate Vaillant Modbus TCP to BACnet IP — the Anybus gateway is pre-configured by the systems integrator with the Vaillant VWZ AI register map. Alternatively, for Niagara projects: the Niagara Modbus TCP driver reads Vaillant registers natively without an additional gateway, exposing them as Niagara points that can then be published to BACnet if needed. For purely KNX commercial projects, the Weinzierl KNX ENO 634 or Intesis IBOX-KNX-MBS gateway handles Modbus TCP to KNX translation directly, avoiding a BACnet intermediate step.
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