E9 error. No power detected in C wire E79.

[gsam]

Hi followed the suggestions made ..

Nest Learning Thermostat is compatible with the wiring you have. The brown wire connected to the B terminal  is a common wire.    You can check this wiring guide: (Note: You don't need to use any jumper wires)   White wire to W1 Nest terminal Yellow wire to Y1 Nest terminal Green wire to G Nest terminal Blue wire  to OB Nest terminal Brown wire to C Nest terminal Red wire to RC Nest terminal.

i am getting an error E79 - No power to connect C wire. 

 

 

 

 

[Patrick_Caezza]

I'm not sure who provided the wire instruction to you, but the Tan B wire is not a C wire.

The zone control system that you have will only work with thermostats provided by EWC Controls. These specific thermostats use both the O and B wires to control the HVAC system and none of the Nest thermostats are compatible.

ST-2 & ST-3 Manual 

[gsam]

Thank you @Patrick_Caezza 

So what are my options here to make the Google nest work? Do I need to upgrade zone control system? Can you please share some insights?

[Patrick_Caezza]

Upgrading the zone controller can be expensive since you will most likely need to replace the damper modules along with the controller.

I can't offer any more help beyond that.

[Markjosephp]

Hello there,

I wanted to stop by and see how I could help.

Thanks for the help here, @Patrick_Caezza.

@gsam, I'm sorry for the late reply. I know it's been awhile, but I'd love to know more about this.

Is your Nest Thermostat still installed? Could you please check its power readouts under the Technical Info settings with and without the C wire connected? If your thermostat doesn't show the same wiring report without the common wire, leave it disconnected, as your common wire may not be properly grounded, so the system uses power sharing but doesn’t get enough energy.

Please let me know if that helps.

Regards,

Mark

[Markjosephp]

Hi gsam,

I'm checking back in — how's it going? Did leaving the C-wire help?

Regards,

Mark

[Markjosephp]

Hello gsam,

It has been a few days since your last reply, and we're going to lock the thread within 24 hours. If you have any questions, please feel free to create a new post.

Thanks,

Mark