Thermostat stopped connecting

[Slambr]

I’ve had my Nest 3gen thermostat working fine for years. This summer I added a new water heater so I could turn the boiler off during the summer. I just turned it back on and can’t get my Nest to heat the house. It connects, turns on, but within a few minutes says the Rh connection can’t be found. The wiring was never touched. This is not a new connection. Can someone help or tell me who would I call to help? Electrician? Plumber? Heating/oil guy? Do I need to replace my Nest? Maybe with a new brand? TIA

[Patrick_Caezza · Accepted solution]

If you had the boiler turned off for an extended period of time, there is a very good chance that the internal battery has completely discharged. Try using the USB port on the thermostat and any phone charger to charge the battery in the thermostat. You'll most likely need to leave it plugged in to charge for several hours or even overnight.

[Patrick_Caezza · Accepted solution]

If you had the boiler turned off for an extended period of time, there is a very good chance that the internal battery has completely discharged. Try using the USB port on the thermostat and any phone charger to charge the battery in the thermostat. You'll most likely need to leave it plugged in to charge for several hours or even overnight.

[Slambr]

Thanks. I charged for several hours and it still connects, the heat kicks on, but still stops after a few minutes - it says Power Out. I’ll charge it overnight and see if that does the trick. I also ordered a new battery but it’s not expected for another week. I’m assuming that since it’s turning it on at some point it’s not a connection problem but as you suggest it must be the battery. I have a 3rd Gen Learning thermostat. Only 2 wires W1 and Rh are connected. Thank you. I’ll keep trying. 

[Patrick_Caezza]

Those two wires are your problem. You are going to need a C wire, and the Google Nest Power Connector is the easiest way to add it.

There are no replacement batteries for the Nest Learning Thermostat, 3rd Gen. I know people sell what they claim to be a replacement battery, but they are the wrong voltage and current rating, they also tend to be the wrong physical size.

This is the basic wiring that you'll need to do to use the Google Nest Power Connector.

 

[Slambr]

So even though this has been working for six years I now need to purchase the Power Connector? Is it because of the battery or is it because I put in a water heater for the first time (boiler had on demand hot water but it didn’t get hot enough). Do you know?

I’m not familiar with wiring, is this something that my I can do (or my handy boyfriend) or does it require adding wiring down to the basement? I’m in a 1946 colonial with radiators and no central AC, if that helps. 

Last question, if I have to hire someone to do the wiring, if this were your house, would you just purchase a new thermostat since it’s already 6 years old or stick with the Connector?

Thanks in advance. 

[Markjosephp]

Hi folks,

Chiming in. I just wanted to see how I could help.

Thanks for your assistance @Patrick_Caezza. That helps!

@Slambr, I understand that you've been using your Nest thermostat for several years without having any power issues until the recent change to your system. Let's see what's going on.

A few questions: are you getting any wire reports or message codes? If so, what's the message? Then, please try the troubleshooting steps here:

1. Check the battery level, Voc, Vin, and Lin in Power under Technical Info settings.
2. Turn off the system power from the beaker before touching the wires.
3. Remove the thermostat display from the base.
4. Move the Rh wire to Rc terminal.
5. Make sure both wires are still connected.
6. Put the display back to base, make sure it'll click into place.
7. Then, turn the system power back on and check your thermostat for any wire reports.

Let me know how it goes.

Best regards,

Mark

[Markjosephp]

Hi Slambr,

I'm checking back in. Were you able to do the steps above? I'd be glad to hear from you — I'd like to make sure everything is working.

Best regards,

Mark

[Slambr · Accepted solution]

Hi Mark. Thanks for checking in. The problem is solved. I replaced the Nest with a dumb thermostat and that also worked for a few minutes and shut off. The plumber came back and said I probably needed a transformer - which the boiler company also said I’d need. However I then called the oil company who installed the boiler 12 years ago and said (based on all the troubleshooting I did he figured it out pretty quickly) it came down to the thermostat still being connected to the boiler for the on-demand water. Once it hit 180° it would shut off. He removed that wire from the boiler, put the Nest back on and it works just like before I added the external water heater. Two wires and it works. I am returning the Power Connector tomorrow. It shouldn’t be working based on all the literature but it does. And I love having it back!

[Markjosephp]

Hi Slambr,

That's great! I appreciate you posting and updating us on your efforts to address your concern finding a fix— Hats off to of you!

So I'm going to be locking this thread in 24 hours. If you have any other concerns or questions, please feel free to create a new thread.

Best regards,

Mark