Ouman
Finnish HVAC Building Management with EH-203 and KNX Integration
Ouman (Oulu, Finland) manufactures building management controllers (BMS) for HVAC automation in Nordic markets. The Ouman EH-203 (heating curve controller), EH-800 (multi-function BMS controller), and SummIT web-based BMS are widely used in Finnish apartment buildings, schools, and offices with KNX building automation.
Role in our panels
How we use Ouman
Ouman EH-203 KNX integration: The EH-203 is a standalone heating curve + domestic hot water controller with RS485 Modbus RTU. Unit ID 1, baud 9600, 8E1. Key registers: 1 (outdoor temperature, int16 degCx10), 2 (heating circuit 1 supply temperature setpoint, int16 degCx10), 3 (heating circuit 1 actual supply temperature), 10 (DHW setpoint temperature), 11 (DHW actual temperature), 20 (operating mode: 0=normal, 1=setback, 2=holiday, 3=anti-freeze), 21 (heat pump ON/OFF 0/1). Write register 20 from KNX time programme (schedule to Modbus write mode). Write DHW setpoint (reg 10) from KNX for SG Ready boost. Ouman EH-800: multi-channel HVAC controller (up to 8 heating zones, 4 AHU controls). RS485 Modbus RTU unit 1. Also has BACnet MS/TP on second RS485 port — bridge via LOYTEC for KNX. Ouman SummIT: web BMS with OPC UA and Modbus TCP (port 502). MDT Modbus gateway polls SummIT for energy counters, setpoints, and alarms. KNX demand-controlled ventilation: Ouman reads CO2 from Modbus-connected sensors, KNX sends occupancy telegrams from motion sensors (MDT PIR) to Ouman Modbus write registers 50-57 (zone occupied 0/1) — Ouman then adjusts AHU fan speed accordingly. Nordic climate considerations: heating curve parameters (e.g. EH-203 curve slope 1.8 at -26 degC outdoor) critical for Finnish climate — KNX weather station outdoor temperature feeds directly to KNX GA, but EH-203 reads outdoor temperature from its own NTC sensor.
Ouman EH-203 and EH-800 controllers integrate with KNX via Modbus RTU RS485 (9600/8E1), with KNX writing operating modes and setpoints to Ouman and reading temperatures and heating state for building-wide visualisation.
Used in these project types
Ouman products
Key components we install
EH-203 Heating Curve Controller
Standalone heating curve controller for district heating and boiler substations. RS485 Modbus RTU (9600/8E1, unit 1). KNX writes operating mode (reg 20: 0=normal, 1=setback) for schedule control. Reads outdoor temp (reg 1) and supply temp (reg 3).
EH-800 Multi-Zone BMS
8-zone HVAC controller with RS485 Modbus RTU and BACnet MS/TP. Controls multiple heating circuits + AHU. KNX integration via BACnet MS/TP to KNX bridge (LOYTEC LGATE-930) or Modbus TCP via SummIT platform.
SummIT Web BMS
Ouman SummIT web-based building management system with OPC UA, Modbus TCP port 502, and REST API. Aggregates EH-203/800 controllers on RS485 bus. MDT Modbus TCP gateway reads SummIT for KNX energy and alarm integration.
Ouman FAQ
What baud rate and parity does Ouman EH-203 use for Modbus?
Ouman EH-203 uses 9600 baud, 8 data bits, even parity, 1 stop bit (8E1). This is the Nordic standard RS485 configuration. Unit ID is set on the front panel DIP switches (1-31). The GOLD Swegon AHU and Ouman EH-203 in the same building must use different unit IDs on the same RS485 bus.
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