If you dive into the details there&#x27;s a ton of disclaimers, limitations, and gotchas running without the C wire. See [0] amongst others. As I said above, I do not recommend.<p>Just because you CAN do something doesn&#x27;t mean you SHOULD. This is definitely one of those cases. If you want your Nest to be running problem free on most systems (or any other smart thermostat for that matter), just assume you need the C.<p>[0] <a href="https:&#x2F;&#x2F;nest.com&#x2F;support&#x2F;article&#x2F;When-Nest-needs-a-common-C-wire" rel="nofollow">https:&#x2F;&#x2F;nest.com&#x2F;support&#x2F;article&#x2F;When-Nest-needs-a-common-C-...</a>