OpenTherm Gateway

New product

OTGW (OpenTherm GateWay) is based on an open source project by Schelte Bron. You will find more information on this website: 

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27,50 € tax incl.

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Fabrication time is 1 week upon placing an order.

OTGW (OpenTherm GateWay) is based on an open source project by Schelte Bron. You will find more information on this website: 

Another source for information is the Domotica OTGW forum: OTGW Forum

On OTGW boiler and thermostat matrix you will find a list of boilers and thermostats compatible with the OTGW print, and also which functions are supported.

During normal operation, the OTGW will communicate with the boiler and the thermostat via the two-wire link: the OTGW must be installed between boiler and thermostat. For programming, the OTGW can be linked to your computer using an FTDI cable,Wifi or ethernet  connection (can be purchased separately: cable, Wifi or UTP unit are not part of the OTGW unit). On delivery, the OTGW unit contains a pre-programmed PIC with the latest firmware. Tools and future firmware can be downloaded from OTGW download (

Supported features:

  • Monitor and log Opentherm communication between boiler and thermostat
  • Change thermostat temperature setpoint
  • Add outside temperature to thermostat display (if supported by thermostat)
  • Read outside temperature sensor
  • Control hot water supply (if supported by boiler)
  • Supports the following situations:
    • Opentherm thermostat
    • On/off switching thermostat
    • No thermostat present

Note that for several of these functions you will need a controlling program, for instance Domoticz.

The OTGW kit is sold as DIY kit. However, most of the components are SMD and are already installed on the printed circuit. Only the connectors and headers need to be installed. If you dont want to do any soldering yourself, you can choose for the soldering service in the webshop. The OTGW will then be delivered fully installed and ready for use. All OTGW units are fully tested before shipping. You can find it on the following link:

Opentherm Gateway Solder Service

The OTGW draws its power from an external 24V power supply. You may be able to re-use a power supply you already own, or you can purchase it separately from the webshop. The advantage of using an external power supply: there is no mains power (115/230 Volt) present on the OTGW print, which improves safety.

There is now a dedicated NodeMCU firmware for the OTGW board with NodeMCU. You can find all the info here:


Optionally you can order these items:

All of these articles can be found on the Nodo Webshop (


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