Nest Thermostat No WiFi and Hot Water Relay Sticking on

[lowbug]

Hi, we have two nests which work independently. One for upstairs and one for downstairs. They are installed 4 inch's away from each other, upstairs works fine and never loses WiFi connection.

both best were bought the same time October 2023

We noticed downstairs, occasionally drops WiFi, however it is getting worse. Also we found the unit is energising the hot water relay. We can prove with a multimeter we have continuity on the normally open pins. It seems to do this randomly, today we caught it again firing the boiler at around 4am, there has never been a schedule for this time !

The unit has been reset and we also reset to factory. Still playing up. We try to search for WiFi network and it can't see any despite there being an WiFi access point 1 meter away and another nest unit connects with no issues to this access point?

We think the unit is breaking down internally as there are two significant issues with it. The relay should not be operating and we can see on the dial screen the thermostat is not asking for heat / hot water? 

We tried a google support form but it says it's out of hours when it is in hours. Please help.

[Patrick_Caezza]

@lowbug 

Where are you located? US/Canada or UK/Europe?

How are the thermostats wired?

Can you post pictures here?

Are you controlling just the hot water relay?

[Frustratedddd]

I assume you are in the UK the way you are describing things, and assume you are talking about the relays in the Heat Link - Correct?

Instead of trying to connect an access point, try the Hotspot in your mobile!

This will prove if you are having issues with your home wifi. We have to start somewhere. Also IF you are in the UK, don't contact Google support yet until you confirm the above.

[lowbug]

Hi, Yes UK. Sorry, the relay output on the heat link. So we did a full factory default. Wifi set back up and the thermostat was quicker to use ( odd) it was laggy before. After the full factory default, it was quick and found the wifi ok. So it was working okay until a moment ago around 12 hours later when we heard the heating on. We also noticed the Wi-Fi had disconnected.  We have two nests and both heat links are next to each other. The other nest is working with no issues, this one is constantly having wifi issues dropping out for no reason. 

We will try another WIFI access via a mobile - good idea 🙂 

Does the Heat Link connect to wifi or is it the wall mounted thermostat? 

[Frustratedddd]

The display connects to WiFi, but it’s always recommended not to connect via access points. Metal objects, ie fridge, microwave etc., are all objects that block signals. Look for something that may have been replaced recently!

[lowbug]

Thanks, We have a wireless mesh network due to the size of the property. Its just done it again. I got out the fluke multimeter and we have 247 Volts on both pins on the nest heat link relay. The other heat link is not like this. We checked the display and its not set to come on. We noted the minute the nest lost wifi, it turned the boiler on!

Could this be a setting? Not sure this is right imagine turning your router off when you go away to come back and find your heating has been on for 2 weeks?

Odd thing is the display is  6-meter line of sight to an access point in the same room ( Lounge ). When it was connected to the unfi access point it had a "excellent" signal.

[lowbug]

@Patrick_Caezza Thanks - I said hot water in the topic but it's also doing the same to the radiator heating. When it loses internet connection, the heat links the relays so the normally closed is then at approximately 247 volts. If we check the display it is set as hot for both water and radiators. We did a full factory default (again) earlier and it's behaving the same way as it was before. It also seems to be getting progressively worse. When it does this it somehow cuts the wifi off and then the relays energise or the lack of wifi causes it. unsure to which way it truly is..

Rebooting it brings wifi straight back on then after a few hours the relays energise and we have no wifi to the nest? 😞

[Patrick_Caezza]

@lowbug 

I know nothing about how the heat link system works so I can't be of any help.

Sorry

[lowbug]

We tried to get the nest to connect to wifi - it wouldn't. We then restarted the nest and it did the " I will be back in a bit". We then checked wifi and it was connected again to the signal to the closest unfi AP. This means the nest is connected to the access point 6 meters from it across an open lounge. It has a signal rating of excellent.  Thanks for everyone's help 🙂

[Frustratedddd]

You mention UniFi, I have the same and use to connect to the nearest AP at 5mhz, I changed that to 2.4, that did help. Sadly the connection still had issues, and then connected direct to the router at 2.4, and that has worked ever since. Nest always recommend connection direct to the router. 

Your thermostat is it wired or wireless?

I am not saying this is your issue, as I can’t see why the system would kick in randomly. Was the time correct on the display or had that changed? 

I would try a full reset, and then check all schedules have been removed.

Who installed the system, ie Nest Pro?

[lowbug]

Hi,  Ok so working from home and the upstairs nest ( different nest ) is coming on! No schedules - everything is in eco. Is there an issue with this product? We disconnected all wiring from the heat link and we have 248 volts from the hot water terminals! Nothing is telling this nest to operate. App shows everything is off.

Losing faith in this system. The control system should run by command not randomly come on without warning!

[lowbug]

I've been on with Google Nest support via the phone, they are both factory defaulted. They were not connected to the app and asked if I could leave both units 24 hours. Already with no schedule setup and the thermostat set to eco 9 deg c  ( its 20 in the house ). Randomly we caught one of them turning on the heating at 8:40pm. Checked the thermostat no schedule and it's not orange. checked with the multimeter and the heat link has the relay activated (the wire is disconnected on the other end to prove its not back feeding.. )

It looks like there are some serious and dangerous issues with Nest. There is nothing connected and the thermostat/switch is set to off, yet the unit is turning the relay on and working!

I think the best course is to rip it out and put in a more reliable system... google is saying they will send another two units - but two units failing is very worrying, with no clear answer I am worried this is either a known issue they are covering or they have no idea what's going on.

[Frustratedddd]

Who installed these thermostats for you? Not a name.

Are you saying, one Thermostat and Heat Link is working correctly, and one not still?

Have you a picture of the Heat Link connections?