Please call to check availability before ordering Live Chat/01985 850982

The Viessmann Internal extension H2 is a versatile function extension that allows for external extractor interlock and various connections, such as DHW circulation pump, heating circuit pump, central fault message facility and cylinder heating pump. Easily control and enhance your system’s performance for ultimate efficiency.

• External extractor interlock, or alternatively, one of the following functions:
• Connection of a DHW circulation pump (only with Vitotronic 200)
• Connection of a heating circuit pump (stepped) for a directly connected heating circuit
• Connection of a central fault message facility
• Connection of a circulation pump for cylinder heating