https://www.googlenestcommunity.com/t5/Nest-Thermostats/3-wire-connection-only-cools/m-p/101517#M22602 <P>The old thermostat uses 3 wires, G, Y, and Rh jumped to Rc.&nbsp; The house was originally zoned oil hot water with 2 wire thermostats plus AC &amp; air handlers added later.&nbsp; Connected as instructed only fan &amp; cool can be accessed.&nbsp; At another location, Nest works fine and I can access the setup for the zoned heat (this uses a different air handler AC).</P> Tue, 08 Feb 2022 13:42:13 GMT John78 2022-02-08T13:42:13Z https://www.googlenestcommunity.com/t5/Nest-Thermostats/3-wire-connection-only-cools/m-p/101517#M22602 <P>The old thermostat uses 3 wires, G, Y, and Rh jumped to Rc.&nbsp; The house was originally zoned oil hot water with 2 wire thermostats plus AC &amp; air handlers added later.&nbsp; Connected as instructed only fan &amp; cool can be accessed.&nbsp; At another location, Nest works fine and I can access the setup for the zoned heat (this uses a different air handler AC).</P> Tue, 08 Feb 2022 13:42:13 GMT https://www.googlenestcommunity.com/t5/Nest-Thermostats/3-wire-connection-only-cools/m-p/101517#M22602 John78 2022-02-08T13:42:13Z