Nest gen4 works without common

[jlv]

My nest works fine without common connected at t-stat or furnace.   How?   

[Derickf]

Hi @jlv,

Thank you for posting in the community. I understand you have questions about how your Nest Thermostat (4th gen) works correctly without a common “C” wire connected. I'm happy to share more information with you.

This behavior is possible because the Nest is designed to "power steal" or draw residual power from other low-voltage wires when the C-wire is absent. Although we always recommend connecting a C-wire for optimal stability.

Let me know if you have any other questions.

Best regards,

Derick.