E79 code after power outage: how to remote reset?

[ChristinedT]

Hello,

I read in other posts to take the thermostat off the wall and the error code does indeed disappear. My question is, how do this reset remotely? I am away from home 2w at a time. I need to prevent freezing if this error means my furnaces will not work until i take the thermostats physically from the wall…

[CoolingWizard · Accepted solution]

@ChristinedT , the E79 error indicates they the Common wire (C) has lost it connection.  This can be a power sharing issue or an electrical short of some type.  Simply removing the display and putting it back on would not correct an electrical short or a power sharing problem.  Your problem needs closer investigation by a qualified HVAC service technician. 

AC Cooling Wizard

[ChristinedT]

This does not answer my question. My technician installed them and their is NOTHING wrong with the connection. The issue is that after a power outage, the thermostat needs to be taken off the wall to reset to normal function. This has been reported in this community and is indeed the fix to the problem. However, I cannot do this physical reset remotely. My thermostats are being returned. This is a huge problem for me as power outages are fairly common in my area and I am away from home for days, including at -30C in wintertime.

[CoolingWizard]

I am pretty sure why your system does that. My Nest simply restarts after a power outage.  Of course I have a Common Wire and verified the power is 200mA of power.  In your case the battery is fully depleted and then the Nest might need to reinitialize itself and hence the remove and reinstall. It is causes the Nest to retest the wires and verify each is correctly operating.  Fix your common wire and will no longer have this problem.  

AC Cooling Wizard

[ChristinedT]

Thanks for reading and answering. Batteries were completely charged and voltage over common wire was tested and amperage within range.
My previous thermostats ran on the same common wires.

Bought T9s instead… they work fine. Even when I cut the power.