Thermostat not working H72 error

[Princess_Pia]

I am in Australia and have a nest learning thermostat 3rd Ed that I purchased online from the UK. I have hydronic heating that it controls. I am getting the h72 error which I know means no power is getting to the thermostat. My thermostat is hard wired and I can’t find/ don’t know where the heat link is installed to check that. The nest was installed as part of a new build and I have been in the house for over 2 yrs and have never seen the power link. I’m presuming the thermostat needs the power link to work so I must have one?? ‘I’ve checked the fusebox (all fuses ok, no power link there) and also the boiler has power. 

any ideas? 

[AlexD]

Thanks for reaching out to us here @Princess_Pia . I would be happy to try and assist. 

You are correct, the H72 is a message that indicates missing power to the display. 

Just to confirm, if you grab the display by the rotating ring and pull it off the base, does the base under it only have 2 wires going into it, T1, T2 terminals, or multiple ones? 

If you do only see 2, then it is the model that uses a Heat Link and if the display is wired to the Heat Link, then that is what provides power to it. You will need to locate the Heat Link to see what the status of it is, it should have an LED light on it if it is still operational. 

If you are not able to locate it you may want to get in touch with an installer, they may be able to trace the wires to its location. You can have a look here to get an idea on how the Heat Link should look for each of our thermostats. 

[Princess_Pia]

Thanks. It has the two wires. I have reached out to the company, hopefully they have a note of where it was installed!

[AlexD]

No worries. In that case it is definitely the model with the Heat Link. Once you manage to locate it make sure to let me know. Make sure to note the status of the LED lights on it. 

[AlexD]

Hi, just wanted to check in. Did you manage to locate the Heat Link? Keep us posted once you do.

[Princess_Pia]

The installer has told me where they think it is, but we haven’t had a chance yet to investigate (not easy to reach). Hoping to do it this weekend…will keep it updated 

[AlexD]

No worries. Keep us posted here on how it goes. Just remember it is a white box with a button in the middle of it. And usually it will have a status LED on but it might not have one on.

[Princess_Pia]

We found it. No LED lights on. We rest it but still no lights came on so i’m guessing it has died?

[UanaC]

Hello @Princess_Pia ! 

Indeed this might be the problem. Let's find out. Could you please answer to the following questions:

1. How long has your thermostat been installed for?
2. Have you had any power cuts recently?
3. Have you had any work done on your electrical or heating systems recently?
4. How many zones are present in the setup?

Many thanks, Oana.

[Princess_Pia]

1) installed mid 2020

2) no

3) no

4) 1

[UanaC]

Thanks! Could you also confirm or try the following troubleshooting steps:

1. Check if all the breaker switches are set to on.

2. Turn the breaker switches off and back to on.

3. Try to turn on manual mode by pressing once on the Heat Link.

[Princess_Pia]

Hi,

yes have checked all the fuses are switched on and tried switching them on and off.

pressed once initially on the heatlink and got not response so then held the button for 10sec to reset it with no effect

[UanaC]

Gotcha! I've sent you an email with more instructions. Please follow them and let me know once it's done.

[Princess_Pia]

that’s complete now

[UanaC]

Thank you so much for doing this! I just sent you another email. Please let me know if there are any questions.

[OannaCG]

Hi there! Just checking in, did you manage to see the message above?

[Princess_Pia]

Yes i did, thanks

[OannaCG]

Great! Is there anything else we can assist you with for the moment?

[Princess_Pia]

No, just waiting for the follow up from the case being transferred

[AlexD]

Thank you for your patience. I just finished checking in with my senior colleagues. I will reach out over email with all the details soon. 

[Paul_R]

Hi there! I saw that this issue is now being handled via email, so I'll go ahead and close the thread. Please check your inbox for any updates or steps. If anything else comes up, feel free to reach out here as well. Have a great day onward!