Johnson Controls

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Metasys is Johnson Controls' flagship building management system — the platform spans field controllers (FX/FC series), supervisory controllers (NCE), and enterprise server software (Metasys System Configuration Tool, Metasys UI). The legacy N2 bus (proprietary serial, 9600 baud, RS-485 physical) is the foundation of millions of existing Metasys installations. Migration to BACnet/IP is achieved via the Metasys Software Engine (MSE): the MSE acts as a BACnet/IP device presenting all legacy N2 devices as BACnet objects. Modern Metasys FX-PC and FC field controllers are natively BACnet/IP and MS/TP without N2 migration requirements. York YVAA variable-speed air-cooled chillers support BACnet/IP via an optional BACnet module (factory-installed or field-fitted). Key BACnet objects: Analog Value AV-0 (Chilled Water Setpoint, read/write, DPT 9.001 equivalent), Analog Input AI-1 (Leaving Water Temperature), Binary Input BI-0 (Chiller Run Status), Binary Input BI-1 (Fault Active), Analog Input AI-5 (Compressor Power kW). These objects are browseable via any BACnet/IP client including LOYTEC LGATE-952 or Intesis INBACKNX gateways. LOYEC LGATE-952 gateway configuration for Metasys/KNX integration: add Metasys NCE or FX-PC as a BACnet/IP device in LGATE web configurator. Browse the BACnet object tree — Analog Inputs for measured temperature and power values, Binary Outputs for chiller start/stop commands, Analog Values for setpoint writes. Map BACnet objects to KNX group addresses: York YVAA chilled water setpoint (BACnet AV-0) → KNX GA with DPT 9.001 (2-byte float), chiller status (BACnet BI-0) → KNX GA with DPT 1.001, fault active (BACnet BI-1) → KNX GA with DPT 1.005 (alarm), compressor power (BACnet AI-5) → KNX GA with DPT 9.001. For projects where KNX is the primary room control system (lighting, blinds, room temperature) alongside a Johnson Controls Metasys HVAC plant, two integration architectures are available: (1) LOYTEC LGATE-952 at field level — real-time bidirectional KNX/BACnet mapping with sub-second response, suitable for setpoint control and alarm annunciation; (2) Metasys OPC UA server (v11+) with KNX Virtual OPC UA client — supervisory-level integration for energy dashboards and setpoint scheduling without real-time requirements. Architecture (1) is recommended for KNX room panels in hotels and offices where the chiller setpoint is adjusted from the KNX BMS visualisation or from a KNX room controller.

Johnson Controls Metasys N2 (legacy serial bus) converts to BACnet/IP via Metasys Software Engine (MSE). Modern Metasys FC/FX/NCE field controllers natively support BACnet/IP. LOYTEC LGATE-952 connects as BACnet/IP client: add Metasys device, browse object tree (Analog Inputs for measured values, Binary Outputs for commands), map to KNX GAs. York YVAA chiller BACnet: AV-0 Chilled Water Setpoint (read/write), AI-1 Leaving Water Temperature, BI-0 Chiller Status, BI-1 Fault Active, AI-5 Compressor Power kW. Map to KNX: setpoint GA DPT 9.001, status GA DPT 1.001, fault GA DPT 1.005, power GA DPT 9.001.