E74 - Wiring Report error

[Amber_3110]

We are trying to hook up are gas fireplace to the Nest Learning Thermostat (3rd gen). We did the compatibility check and this thermostat is compatible with our system.

We keep getting the error code E74 - No power to Rh wire detected. The wire is connected. We have a V in of 23 and V out of 23... The wire is properly installed. 

We had another programmable thermostat installed prior to this one without issues.

Any help with this is greatly appreciated!

[moralesvicente]

Hello Amber_3110, 

Thank you for taking an interest in our community. I’m sorry to hear that your Nest Learning Thermostat 3rd Gen is showing the error code E74. Don’t worry, I’m here to assist you. 

Please answer the following questions to help me assist you more efficiently.

• Could you attach a picture of your wire system? 
• What model is the previous thermostat? 

In the meantime, try to perform these steps. 

• Verify the Power Source: Locate the main power switch for your heating/cooling system and ensure the switch is turned on for both heating and cooling, if applicable.
• Verify Thermostat Function: Once the power is confirmed, examine your thermostat. Check if the thermostat is displaying any error messages or unusual behavior.
• Safety First: Turn off the power to your system at the breaker or fuse box.
• Remove the Thermostat Display: Carefully detach the thermostat's display.
• Inspect the wiring:

1. Ensure each wire is fully inserted into its connector.
2. Verify that every connector with a wire is in the down position.
3. Check that 6 mm (⅜") of wire is exposed for each connection.

• Restore Power and Test:

1. Turn the power back on to your system.
2. Observe if the thermostat is functioning correctly.

• Additional Check (if necessary): If the issue persists, inspect the wire connections on the system board.

I'll look forward to your response.

Best regards, 

Daniel 

[Amber_3110]

Hi Daniel,

I can confirm that the wires are properly exposed and connected in each connection. That steps was recently done by a license technician. 

I have attached the wire system.  The previous thermostat that was being used was a Garrison model MC6003.

 

 

Thanks for your help!

[moralesvicente]

Hello Amber_3110, 

Thank you so much for keeping me updated. 

• To ensure your thermostat is correctly wired, I suggest contacting a Nest Pro for expert assistance with the wiring configuration.
• You can also reference this article for a detailed guide on wire identification and connection: Identify a thermostat wire.
• If you need further help, please don’t hesitate to contact us. A representative will be happy to assist you.

Let me know if you have any other questions.

Best regards,

Daniel