Viessmann 0-10V OpenTherm Input Module

Quick guide from the manual

This document provides installation and operational instructions for the Viessmann 0-10V OpenTherm Input Module (Part No. 7249 069). This module is designed to accept a 0-10V DC modulating input signal and transmit it to the boiler via OpenTherm communication. Important: Installation, adjustment, and service must be performed by a licensed professional heating contractor. Ensure the main power supply is deactivated and the main gas supply is closed before starting work.

Product Description

The module acts as an interface between a room controller and the boiler. The room controller calculates the heat demand and sends a signal to the boiler, which then adjusts the heat input accordingly. It is compatible with Vitodens 100, WB1A series, WB1B CombiPLUS series, B1HA, and B1KA series boilers.

Operating Characteristics

The boiler target temperature is determined by the DC voltage input:

• Cut-in (Start): The boiler starts when the signal is at least 2.2V.
• Cut-out (Shutdown): The boiler shuts down when the signal falls below 0.9V.
• Modulation: Voltages between 0.9V and 2.2V maintain the supply temperature of 81°F (27°C).

Installation

1. Remove the left white cover of the Input Module.
2. Remove the black cover of the Input Module.
3. Loosen the two screws and gently pull the module off its sub-base.
4. Remove the required number of knockouts. Install the supplied strain reliefs and guide the wire harness into the terminal box.
5. Mount the terminal base onto the wall close to the boiler.
6. Make electrical connections as specified in the wiring diagrams.
7. Run the Input Module communication cable (2-wire 18AWG) through the Power Pump Module to the boiler control sub-base (Terminals X3.3, X3.4 for WB1A; X21.1, X21.2 for WB1B CombiPLUS; or X21.1, X21.2 for B1HA/B1KA).
8. Connect the power supply harness to the RT terminals in the Power Pump Module (Terminals X4.3 and X4.4). Note: B1HA/B1KA series requires an external 24VAC power source (field supplied).

Wiring Diagrams

Refer to the specific wiring diagram for your boiler series (WB1A/WB1B or B1HA/B1KA) provided in the full documentation to ensure correct terminal connections for the 0-10V signal, OpenTherm (OT), 24V power, and fault alarm output.

LED Display Status

The module features three LEDs to indicate status:

• Red: Fault alarm output (dry contact), maximum 1A (Terminals 18-19 closed).
• Yellow: Call for heat.
• Green (flashing): Bus communication established between boiler and Input Module.

Troubleshooting

If a fault occurs, check the display window on the boiler control unit:

• Fault A9 (Red light flashing): Indicates a communication error. Turn the boiler OFF, then ON. Check the communication cable on terminals X3.3, X3.4 or X21.1, X21.2. Verify connections on Input Module terminals 12 and 13. Check the 24VAC output of the Power Pump Module. Ensure the 0-10V input signal is at least 3.0V to start the boiler.