E79 error on nest thermostat learning

[srhsieh]

I installed the nest thermostat.

My house has two zones -

The system worked well, until about two months ago, (therefore, the system works in the summer time, A/C)

The E79 error message showed up.

Within this community, I read some threads and decided to follow the system - turn off the furnace and then turn it back on.

This error disappeared, but then a few days later, E79 came back again.

Therefore, since then, I have been applying this strategy.

I then decided to contact the google support team.

One support staff suggested to disconnect C-wire from the thermostats.

The E79 did not not show up, but every now and then A/C will spin (like you clap fingers).

It is like A/C receives a signal but did not turn on.

I reconnect the C-wire and then contact the nest support team (and then been suggested to follow a link to all E79 error).

At this point, I am desperate. One one end, I feel that the nest thermostat is modern. But on the other end, I should not retire my conventional thermostat since they worked perfectly.

Based on my previous post (the thread which gets closed since I was out of country for two weeks), here are some information displayed on thermostat:

downstairs: Voc: 36.05V, Vin: 36.05Vm Lin 200mA(c)

upstairs: Voc 35.30V, Vin: 35.30V, Lin: 200mA(c), 

After coming back to USA (05/07), I found both thermostat shown E79 error.

I turns the power break (of furnace system) off and then turns it back on. (and I found there is a power outage in my house).

Monday afternoon, both thermostat show E79 error.

I left them alone and called the A/C company to repair the issue.

Two days later (05/11), the E79 error message disappeared on the upstairs thermostat and remains this way since then.

Do not know what to do now.  

Need help.

Regards,

Henry

[Markjosephp]

Hello Henry,

Thank you for reaching back to the Google Nest Community Forum.

I've read your previous thread, and it appears that you're having issues with your common wire that might not be properly grounded, so the system uses power sharing but doesn’t get enough energy. Could you tell us more about what happened after an HVAC technician's visit?

I'll look forward to your response.

Regards,
Mark

[Dan_A]

Hey there,

I wanted to follow up and see if you still need help. Please let me know if you are still having any concerns or questions from here, as I would be happy to take a closer look and assist you further.

Thanks,

Dan

[srhsieh]

Hi Dan,  Do not know how to address the problem.

It is a mystery to the company installed HVAC system at July 2022, about 5 months after nest thermostat been install. 

My observation is 

1. E79 occurred in the winter time. E79 did not show until late December.  At first, I followed the thread (to shut off HVAC system and then turn the power), but few days (2-3 days) later, E79 showed up again. As I mentioned in my previous post, I disconnect the C-wire (as suggested by Roy the nest technical support), which did not work well. 

2. E79 occurred correlated with how often the furnace been used (activated).   I left for oversea trip on Late April and then came back on May 7. I noticed that the house had a power outage (since the Microwave clock is off).  The E79 showed up.  So I shut-off and then power the HVAC system on.  5 days later, E79 showed up again.

3. So I check the wire connection on thermostat. After reconnect the C-wire,  E79 disappeared. 

4. The HVAC company technician stopped by for routine check up.  He checked and made sure the wiring is correct. He commented that the company had worked on nest thermostat many times, and my house is the only one having this problem.  He suggested maybe it is caused nest thermostat. His next step will be if E79 shows up again, he will disconnect all the common wire (on the zone board and thermostat). 

Again, we had tried everything except replace nest thermostat, toss the nest thermostat away (and replace with different system). 

[srhsieh]

Let me state observation #3 differently

3. So I check the wire connection on thermostat.  After check/reconnect every wire on the thermostat,  E79 disappeared. 

[Markjosephp]

Hi srhsieh,

Thanks for letting us know. I appreciate the steps you've taken with your thermostat. We'd like to take a look at this for you.

Could you please fill out this form with the needed information and let me know once you're done?

Regards,
Mark

[EmersonB]

Hello everyone,

@srhsieh, I wanted to follow up and see if you were able to fill out the form? Let me know if you have additional questions.

I appreciate the help, Dan and Mark.
 
Best,
Emerson

[EmersonB]

Hey srhsieh,

We haven't received your form — were you able to fill it out?
 
Thanks,
Emerson

[EmersonB]

Hello srhsieh,

Just one quick final check in here since activity has slowed down. We'll be locking the thread in the next 24 hours, but if you still need help, we would be happy to keep it open. If there's more we can do, just let us know.
 
Regards,
Emerson

[Dan_A]

Hi srhsieh,

We got your form — thanks for filling it out. Our team will reach out to you via email anytime soon. Please continue the conversation there as this thread will be locked after 24 hours.

Cheers,

Dan

[srhsieh]

Confirm. 

I do not understand this policy "locked after 24 hours". If you expect that I am active then you (your group) should provide a timely support to my claim which you (your group) had failed so times so far.

At this moment, I am not sure if I want to keep the nest thermostat (expect the benefit of doubt) since my old Honeywell old fashion ones worked perfectly all right. 

[Markjosephp]

Hello srhsieh,

It's me again. We apologize if this thread was closed sooner than you would have liked, as it has been escalated to our higher tier of support for the next possible options, and they will be the ones to reach back out to you. No worries; I'll leave this thread open until you get assistance.

Regards,
Mark

[Markjosephp]

Hi there,

We know that this has taken some time. Rest assured we're not leaving you hanging. I’ve made a follow-up with our team — I'll get back to you as soon as I have something to share. 
 

Thanks,

Mark

[Markjosephp]

Hi srhsieh,

We truly apologize if this is taking longer than expected to get resolved. I want to thank you for your patience while we work this matter out. You should receive an email update from our Senior support team. Also, I'll lock this thread in 24 hours unless I can help you with anything else.

Best regards,

Mark