OpenTherm Gateway

New product

OTGW (OpenTherm GateWay) is based on an open source project by Schelte Bron with improvements.

Version 2.3 runs from 5V USB power. There is a built in USB/serial converter to allow a PC to communicate with the gateway.

You will find more information on his website: 

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Pre Order

29,50 € tax incl.

More info

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 OpenTherm link: the OTGW must be installed between boiler and thermostat. For programming, the OTGW can be linked to your computer using a USB cable, Wifi or ethernet  (options to be purchased separately: USB cable, Wifi (WeMos D1 Mini) or Ethernet (USR-TCP232-T2) modules are not included). On delivery, the OTGW kit includes 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 a USB 5V 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.

You may wish to order one or more of the following options:

- USB cable to power and/or connect to a USB port.

- USB power supply if you use the WiFi or Ethernet module.

- Housing


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