Compatibility of the 3rd gen. Nest Learning Thermostat with the Bosch Modulating EMS bus protocol

[Manpher]

Hola, recientemente compré una caldera Bosch ("Junkers") "Condens 6000W" con tecnología de modulación (Modulante). ¿No puedo hacer funcionar mi termostato NEST para que sea modulante ?     Parece que solo los termostatos de Bosch son compatibles con su Bus EMS. Quería saber si alguien ha encontrado alguna solución mediante algún dispositivo "OpenTherm" a EMS o me gustaría que algún firmware actualice mi NEST para que sea compatible con este protocolo y estas calderas. Las calderas de condensación son buenos dispositivos para ahorrar algo de gas y este NEST debería ser capaz de comunicarse con todos.

Hello, I recently purchased a Bosch ("Junkers") "Condens 6000W" boiler with modulation technology (Modulating). Can't I get my NEST thermostat to modulate? It seems that only Bosch thermostats are compatible with their EMS Bus. I wanted to know if anyone has found a solution using an "OpenTherm" device to EMS or I would like some firmware update to my NEST to be compatible with this protocol and these boilers. Condensing boilers are good devices to save some gas and this NEST should be able to communicate with all of them.

[humbertogarcia]

Hi Manpher,

Thank you for posting in the community your detailed and insightful report! I truly understand your frustration that your Nest can't modulate with your Bosch boiler. You've accurately identified the core challenge: your Nest Learning Thermostat (3rd gen) uses the OpenTherm protocol, while your Bosch boiler operates on its proprietary EMS Bus.

This difference in communication 'languages' prevents your system from achieving full modulation. At the time, there’s no available information about a firmware update to support EMS Bus. While you're resourceful to consider third-party OpenTherm-to-EMS converters, Google Nest doesn't officially support these, so we recommend consulting a qualified HVAC professional for assessment.

Your Nest Learning Thermostat (3rd gen) can certainly still control your boiler via standard on/off wiring, ensuring your essential heating needs are met. We genuinely value your detailed feedback on this common industry challenge. To ensure your valuable insights formally reach our product teams, please take a moment to fill out our dedicated feedback form.

Your input makes a real difference in shaping our future innovations. Any additional assistance, please count on me.

Regards,

Humberto

[Manpher]

Thanks Humberto,

If there's no way to communicate productively with Nest, I'll likely turn to an unofficial device that converts Opentherm to EMS Bus or purchase a thermostat compatible with my boiler. It's a real shame, since the handling, design, and functionality of Nest Learning are exactly what we always wanted. After trying several devices, it was Nest that solved our problem.

[humbertogarcia]

Hi Manpher,

Thanks for reaching out again. It's good to hear how much you appreciate your Nest Learning Thermostat's (3rd gen) design and handling. I understand you're looking for full modulation with your Bosch boiler.

You've highlighted the core challenge of the proprietary EMS Bus protocol. We understand your need to consider third-party converters or other thermostats for modulation.

Please know your specific feedback, combining what you love about Nest with your essential feature needs, is incredibly valuable. It directly informs our product evaluations. Feel free to submit your thoughts via our dedicated feedback form.

If you need any other assistance, please let me know.

Regards,

Humberto