Nest Renew randomly changes temperature

[idelange]

Hello,

I have the basic Nest thermostat. It's been working fine for years (so there's no issue with wiring or such). Recently, my heating suddenly goes on and my radiator gets very hot, even though:

- Heating mode is OFF

- It's summer and already very warm in the house (25 degrees celsius plus).

- I don't have Nest aware running and my Nest is not connected to Google Home.

- My Nest on the wall is locked, to make sure I didn't accidentally triggered the change myself.

I looked at my Nest and it's suddenly on "manual". Even though I didn't use the app.

Any ideas? 

Best,

Ingmar

[Jenelyn_O]

Hi idelange,

Thanks for reaching out. I'm sorry for the delay. I'd like to know more about it. Could you please provide your Nest Thermostat's power readout? Also, check your thermostat's Energy History.  It might help you see what your thermostat was doing previously.

You can check out the guides below:

Nest Learning Thermostat and Nest Thermostat E:

1. Go to your thermostat Quick View menu.
2. Go to Settings.
3. Look for Technical Info.
4. Select Power.

Nest Thermostat 2020:

1. Open the Google Home app tap the thermostat tap Settings .
2. Select the Device Information.
3. Choose Technical Information.

Best,

Jenelyn

[idelange]

Hi Jenelyn,

Thanks for your help!

This is the Power readout:

Battery
3.915V
Vusb
0.02 V
Vin
11.02 V
lin
200 mA (c)

Weirdly, if I look at the history, it says "no usage" for every day last week.

Regards,

Ingmar

[Jenelyn_O]

Hi there,

Thanks for providing the information above. Your battery level is fine, and your Nest Thermostat detects your C wire. However, your Voc and Vin aren't in their normal range. 

Voc, Vin, and Iin measure the electrical current sent over your system’s wires to your thermostat. 

Below are the ranges that the Voc, Vin and Iin should stay in during normal operation.

Nest Learning Thermostat/E

• Voc: 29 to 42V
• Vin: 29 to 42V
• lin: 100 to 200 mA

Please go to your thermostat's Settings > Equipment > Wiring Diagram. Check for any messages or codes there. 

Also, did you restart your thermostat recently or last week? The missing Energy History data happens because the Nest thermostat went through a non-orderly restart at some point that day. A non-orderly restart simply means the thermostat wasn’t restarted properly by selecting Settings > Reset > Restart in the thermostat interface.

Regards,

Jenelyn

[idelange]

Hi Jenelyn,

When I select Equipment Settings I only see the options heat link / hot water temp / pro setup.

For your understanding: there's no energy history data missing, it just says "no usage". While the radiator did get hot and the Nest suddenly was on manual mode (selected temperature 27.5 degrees Celsius).

The wiring has been like this since I had the Nest installed in 2015, never had problems before.

Best,

Ingmar

[LarisaL]

Thank you for the details. Can you tell me if your thermostat controls the hot water as well? Also, did you notice any patterns when the radiators are on? 

[idelange]

Yes, the thermostat controls hot water also. I just suddenly noticed the radiators were very hot and quickly turned the Nest back to HEAT OFF. It was already a hot day and plus 27 degrees Celsius in the house... 

[LarisaL]

And when the radiators were hot, did you notice on the thermostat display an orange circle with a black water droplet or any other icons? Do you have a separate hot water tank as well?

[idelange]

Hi Larisa, 

Sorry, I seemed to have missed your reply. No, the thermostat display just showed "Manual" and 27.5 degrees celsius. The screen was orange ("heating"). I don't have a separate hot water tank. Both my central heating and hot water are heated by the same gas driven module.

[AlexD]

Thank you for the information. The "Manual" message indicates that the manual mode was activated. This can only be done by pressing the button on the Heat Link. Does anyone have access to the Heat Link location or are there doors or anything that could press the button by mistake? 

[idelange]

The first time, I'm very sure I didn't touch the dial and there was no one else in the house. The second time, I locked the screen with a code, to be 100% sure the dial wasn't touched. It still happened. Could this be a hacker having fun?

[TudorL]

Thanks for letting us know. By any chance, are there any programs or controls on the boiler that may interfere with the controls of the thermostat? 

[idelange]

No, there are no other smart interfaces present and the setup hasn't change for that last few years.

[TudorL]

By any chance, have you used the Auto-Schedule or True Radiant functions on the thermostat? 

[idelange]

No, nothing 🙂

[LarisaL]

Do you remember how many lights have you seen on the Heat Link when this happened? Also, did it happened since then?

[idelange]

I didn't look at them, sorry. It happened twice in two months.

[Paul_R]

No problem. In this case please monitor the issue and let us know if it appears again. The message saying "Manual" on the display can only mean that the manual mode of the Heat Link was somehow activated, this would mean the button being pressed. If this occurs again, please look at the Heat Link and note if it has three lights on. It may be the button that has some malfunction, and somehow activated itself, I couldn't tell really. 

[idelange]

Sorry for my late reply, your reply ended up in my spam. I getting the vibe my Nest was hacked. Again, the display was on Locked and I didn't touch it. Still, it was suddenly on manual and 27 degrees. 

[AlexD]

No worries. The manual mode can't be triggered by the app or from the display itself. It can only be triggered by the button on the Heat Link. So it is very unlikely anyone else could trigger the manual mode as it can only be activated by pressing the button on the Heat Link.  

Just to check, is anything close to the Heat Link like a broom, door or something else that could move and press the button perhaps?

Also, do you happen to still have the plastic sticker over the Heat Link button? If so, do remove it as it could be pressing down on the button slightly. 

[idelange]

Mhhhh... that's interesting. I will look into this, thanks Alex!

[AlexD]

No worries. Keep us posted here!

[UanaC]

Hello there! Just checking in, did you see my colleagues previous message?

[UanaC]

Hello there! Just checking in with you. Did you see my colleague's previous message?