topic Re: H73 error nest learning thermostat in Nest Thermostats

H73 error nest learning thermostat

Klempka — Tue, 27 Dec 2022 09:16:00 GMT

I have Nest Learning Thermostat 3rd gen. and Viessman Vitodens 100 boiler.

For last 3 years its been connected over OT and worked well. Since about 3 months few times error H73 comes up and says couldn't detect an OpenTherm connection, Check your settings.

Few times just a reset of thermostat and heatlink helped but last time I had to reset all settings to factory, restart boiler and it worked for about two weeks. This morning it happened again, same error, same situation but nothing helped to make it work again. Boiler works on normal settings (not over OT but normal request of heating) but I want it back on OT.

Re: H73 error nest learning thermostat

AlexD — Wed, 28 Dec 2022 12:18:54 GMT

Thanks for reaching out to us here @Klempka . I am sorry to hear you are having difficulties with your device and i'd be happy to try and assist. The H73 message indicates that the thermostat is connected to the Heat Link but the OpenTherm connection between the Heat Link is not detected.

In this case I would recommend getting in touch with the boiler manufacturers or perhaps an installer to test the OpenTherm connection terminals. It may need some adjustments in the settings or there could be something going on on the boiler or Heat Link side. There could also be something going on with the e-Bus adapter, if that is how the Heat Link is connected to the boiler.

Re: H73 error nest learning thermostat

george_t — Fri, 30 Dec 2022 15:38:22 GMT

Hi @Klempka. Just checking in, did you manage to read the message from my colleague?

Re: H73 error nest learning thermostat

Klempka — Sun, 01 Jan 2023 12:30:31 GMT

Thank but No errors on the boiler. I bought different thermostat that works on OT and it worked straight out of the box.

anyway, on the same day I posted this tread nest managed to come back to work by itself. It looks like heat link has some reliability problems. It’s becoming more common

Re: H73 error nest learning thermostat

Vladut — Sun, 01 Jan 2023 12:40:06 GMT

Hi @Klempka, thank you so much for the update. It's great that everything is back to normal. i apologise for any inconveniences caused by this. If you need anything else please let me know.

Re: H73 error nest learning thermostat

Klempka — Mon, 02 Jan 2023 01:37:39 GMT

I’m not sure if it’s back to normal. Will find out. As well shouldn’t you guys figure out what is wrong with heatlink? Why is it loosing control over OT? Why is it reconnecting and returning to normal after some time? Is there any software or firmware update?

Re: H73 error nest learning thermostat

AlexD — Thu, 05 Jan 2023 15:57:31 GMT

The thermostat and the Heat Link should update automatically if there is any update. It could have been something related to the Heat Link or it could have been something related to the boiler that was causing the behavior. In order to determine what may be going on we need to try and troubleshoot.

Re: H73 error nest learning thermostat

AlexD — Sat, 07 Jan 2023 16:45:37 GMT

Hi, I wanted to check in. How has it been behaving so far, still going ok?

Re: H73 error nest learning thermostat

AlexD — Sun, 08 Jan 2023 16:49:20 GMT

Hey there, I haven't heard from you in a while so I'll be locking this thread. If you have any new issues, updates or just a discussion topic, feel free to start a new thread in the community. Thanks, AlexD.