Nest Gen 4 thermostat

[fhkrph95]

Love the thermostat, but it does come with a few glitches. I have the t-stat wired for heating only.,.so I connected the Rh, W1 and C wires as instructed. All connections are locked and secure. Even so, I get a continuous error code N403...No Power to W1 wire. In addition ,, the t-stat displays a ....No System Power....on the display. This occurs intermittently , and when it does, the t-stat has no power for about a minute  before powering up again. 

The unit is doing it's job of controlling the heat from my gas furnace, but these error messages are annoying. 

I called customer support about the problem. They sent a new replacement thermostat , but it is showing the same error messages as the first t-stat. The problem was escalated to level 2 technical support, but they could not determine what is causing the error messages and sporadic power cuts to occur. 

So I'm keeping the unit as it is performing it's job of regulating the heat properly and the furnace is responding to all calls for heat. I had a HVAC tech check out the furnace but he couldn't find any issues with the transformer or wiring etc. 

So again very elegant thermostat...but the error codes and sporadic cuts in power to the t-stat are annoying. 

[moralesvicente]

Hello  fhkrph95, 

Thanks for posting here in the community forum. I’m sorry to know that your Nest Learning Thermostat 4th gen is not working as you expected due to this error code that is showing up constantly. So don’t worry; I’m here to assist you today.

 Usually, this error code appears if one of the wires in your thermostat is receiving less power than expected. So let’s check these recommendations.

• Check that all connectors with wires are down; if they aren't, reinsert the wires. Press the connector button down and insert the wire as far as it will go. If the wire is in correctly, the button will stay down when you let it go. You may need to strip the wire ends. There should be ⅓ to ½ inch of straight copper wire exposed.
• Press the display onto the base until it clicks into place and turns your system power back on.

If you have a multi-meter and feel comfortable manipulating the wiring system, you can check if this wire (w1) is receiving enough power.  

When you want to use the voltmeter, you should turn the dial or switch to AC. AC allows voltage to flow through the leads and allows the voltmeter to display an accurate readout.

• Set the dial to 200 VAC or V~. 
  • If the multi meter doesn’t have a 200 setting, choose 100 or 250 VAC.
  • The general rule of thumb is don’t set it too high (500+) or too low (50). Place the red lead on the R wire.
• Place the black lead on the other wire being tested (W1, Y1, or C).
• The normal readout should be somewhere between 20 and 30 V (24 V is most common).

I'll look forward to your response.

Regards,

Daniel

[fhkrph95]

Thanks for your response Daniel.

I had a new 3 wire installed by a licensed HVAC technician and can confirm that all 3 wires are properly and securely locked into place. 

All wires were stripped 1/2 inch prior to insertion and all buttons are staying down. 

Furthermore, my furnace does turn on when it receives a call for heat...so the W1 wire is clearly installed properly and receiving power, despite the fact that I have a continuous error stating "no power to W1 wire detected "

The voltage on the t-stat itself reads Vin : 35.558V...lin:300...PS:C - 300...Battery voltage : 3.935V

All values are within the recommended voltage range as recommended on the Nest website. 

The more bothersome error message is the one that says : No System Power. 

This message only appears intermittently, but when it does, the thermostat goes dark and doesn't function for a minute or two . Then it powers back up and works normally. 

Despite all of these error messages, the thermostat is functioning properly and keeping the heat at the desired setting. 

So again the W1 wire is installed securely and does allow the furnace to turn on when it receives a call for heat...so it should not be triggering the error message : no power to W1 wire detected" if it is consistently allowing the furnace to turn on when needed. 

But the intermittent " No System Power"  events are perplexing as all the voltage readings are within the recommended range when the unit powers back on. 

I'm confident that the thermostat and all wiring are properly installed. 

Regards,

FK

[moralesvicente]

Hey fhkrph95, 

Thank you for taking an interest in our community. I appreciate your continuous communication and the actions you’ve taken regarding this situation.  
To continue with the assistance, the team would like to learn more about this behavior. When you get a chance, please fill out this form and let us know when you’re finished. We’ll have someone reach out to you via email from there. 

Regards,
Daniel 

[No_One]

Hello,

I am also having HVAC heating issues with my 4th generation thermostat. My wiring is Y1, G, W1, C, Rh. My power status is good, Vin: 31.379V, lin: 300, ps: c-300 and battery voltage: 3.928 V The heat mode is turned on the fan turns on but no heat! I've checked the wiring and everything looks correct. I do not get any error messages like others just no heat. Please help!

[moralesvicente]

Hi No_One, 

Thanks for reaching out to the Google Nest Community Forum. I’m sorry to know you're having trouble regarding the heat mode since it is not activating as you expected using the Nest Learning Thermostat 4th Gen. Don’t worry; I would be more than pleased to help.

It's great to know you've taken action on the matter; I appreciate that useful information. So let’s explore some troubleshooting options.

Perform a wire swap: Move the W1 wire to the Y1 terminal.

• At the breaker box, turn off the power to the HVAC system.

• Move the W1 wire to the Y1 terminal, then put the display back on the wall. 

• Turn the power back on at the breaker box.

• Switch to cool mode, but expect heat.

• Check if the system runs. Some systems take time to start up, so wait up to 5 minutes for the heat to activate. 

Use another thermostat: If you have another thermostat available, try installing it in place of the current one. Monitor its performance to see if you encounter the same problems.

Let me know how it goes with the results. 

Best regards,

Daniel 

[fhkrph95]

So I now understand why the E448 : " No System Power" error message is displayed.

This message appears whenever the furnace has completed it's heating cycle and has turned off. 

As soon as the furnace turns off, the message appears on the t-stat....No System Power...because the furnace has completed it's heating cycle....and is not powered on.

It's not really an "ERROR" . 

It's simply saying that the furnace is done heating for now and has turned off ( No System Power ).

Also, this down time period of about a minute after the furnace turns off may be to prevent you from turning up the heat immediately after the furnace shuts down in order to prevent you from restarting it too quickly, which may result in damage to the furnace 

I'm only guessing here, but that may be the reason.

So in conclusion :

The " No power to W1 wire " error message is NOT an error at all.

That message simply appears whenever the furnace is not running because the W1 wire does not need to be powered on until there is a call for heat to the furnace.

Once the furnace turns on, the "error" message "No Power to W1 wire" disappears. 

And...

The "E448 No System Power " only appears when the furnace has completed it's heating cycle and has turned off. 

It's not an error. It's just telling you that the furnace is done heating for now.

Neither of these error messages are actually errors at all.

They are mislabeled as errors when in fact all they are doing is telling you that the furnace is not currently running.

I would speculate that many Nest thermostat customers are confused about this issue because they are seeing "error" messages on their thermostat  and will assume that there is a problem with it...when in fact...it's not a problem at all. 

Let me know if you have any questions.

From my standpoint , I am satisfied that the thermostat is functioning normally now that I know why these erroneously labeled "errors" appear. 

Best regards,

Frank

[MAB1]

I have had the same problem since installing my 4th gen nest, It was driving me crazy and this makes total sense. Now if they can only fix it so that the humidifier running icon will show in the app or on the thermostat when you have the fan scheduled to run that would be great. I have to turn the fan schedule to off to check the humidifier otherwise it just says fan.

[MAB1]

As an aside, I wonder if this Powe Error message will do the same when the AC starts cycling this summer,