Ouman A203
- Loops: 3 (2 heating + DHW)
- Display: graphical, multilingual
- Power / IP: 230 V AC, IP 20 (controller) / IP 44 (with Ouman enclosure)
- Communication: Modbus RTU, Modbus TCP (via add-on), Ounet cloud
Applications
Ouman A203 is widely used in Finland and the Baltic region: substations for multi-family residential, hotel, office, school and industrial buildings. A single controller handles space heating (radiator or underfloor loop), domestic hot water preparation (DHW) with recirculation, and an optional second heating loop (e.g. AHU coil). Suitable for buildings connected to district heating (DH) and for local heat sources such as gas boilers or ground-source heat pumps. Delivery across the EU.
Technical specifications
| Parameter | Value |
|---|---|
| Code | OMA0650 |
| Model | Ouman A203 |
| Type | Electronic weather-compensated multi-loop controller |
| Loops | 3 (2 heating + 1 DHW) or 2 (1 heating + 1 DHW) by configuration |
| Power supply | 230 V AC, 50/60 Hz |
| Power consumption | ≤ 5 VA |
| Ambient temperature | 0 → +50 °C |
| Display | Graphical LCD, multilingual (LT, LV, EE, EN, FI, SE, RU, etc.) |
| Sensor type | NTC 10 kΩ (Ouman TMO/TMS/TMW/TMR range) |
| Digital inputs | 2 (DI1, DI2 — e.g. room thermostat contact, flow switch) |
| Analogue outputs | 3 (0–10 V for modulating actuators) |
| Relay outputs | 3-point actuator control + pump control |
| Communication | Modbus RTU (RS-485) — BMS / Ounet integration |
| Protection class | IP 20 (controller) / IP 44 (with Ouman enclosure) |
| Remote panel compatibility | Ouman Wireless Room Panel, GSMPLUS, Access 4G/LTE modems |
Designer note
Ouman A203 ships with a factory-programmed standard substation application — no separately purchased application key is required (unlike Danfoss ECL 310). All settings — loop count, DHW schematic, pump control, heating curve — are configured through the menu. Modbus RTU is available out of the box for BMS or Ounet cloud integration. If more than 3 loops are needed, choose Ouman C203 or add a second A203 unit.
When to choose Ouman A203
- Standard multi-family or commercial substation with 2–3 loops
- When Ounet remote-monitoring integration is required
- When the controller must work out of the box, without an add-on key
- Projects that need Modbus RTU integration with a BMS (Fidelix, Belimo, Schneider, etc.)
- Compatibility: sensors — Ouman TMO/NTC10 (outdoor), TMS-4M/NTC10 (surface), TMW-50/100/NTC10 (immersion); actuators — Ouman M31A150 / M31C150 (3-point, heating), M41A15 (DHW), and 0–10 V modulating actuators from Belimo, Siemens SAS/SQS, Honeywell.
B2B delivery and logistics
- Delivery across the EU (from warehouse in Vilnius, LT)
- Competitive B2B pricing for projects and bulk orders
- 30-day payment terms for companies (per contract)
- Free technical consultation on sensor and actuator selection
Official Ouman catalog: ouman.fi/tuote/a203
FAQ
Can A203 replace an older Ouman EH-105 controller?
Yes. A203 is the technological successor to the EH-105 / C203 family and covers the same tasks (heating + DHW control with weather compensation), but adds a wider Modbus interface and a multilingual graphical display. When retrofitting, verify the sensor type (all Ouman NTC10 units fit) and the actuator control signal (3-point vs. 0–10 V).
Does it require a separately ordered application key?
No. Unlike Danfoss ECL 310, Ouman A203 ships with a pre-programmed standard substation configuration. Loop count, DHW scheme, pump control and heating curve are adjusted through the menu.
Which sensors are compatible?
Ouman NTC 10 kΩ (25 °C) family: TMO/NTC10 (outdoor), TMS-4M/NTC10 (surface / clip-on pipe), TMW-50/NTC10 and TMW-100/NTC10 (immersion into pocket), TMR/NTC10 (room). Third-party NTC 10 kΩ sensors with a Beta of ~3977 K also work if calibrated in the controller menu.
Is remote access available?
Yes. Ouman A203 connects to the Ounet cloud platform via Modbus RTU + an Access 4G/LTE modem or GSMPLUS. Ounet provides temperature history, remote setpoint control and email/SMS alerts.
Suitable for BMS integration (Modbus)?
Yes. The open Modbus RTU RS-485 interface integrates with Fidelix, Belimo, Schneider EcoStruxure, Siemens Desigo, Ouman Ounet and other BMS platforms. The register map is available from ouman.fi or on request.
