[![enter image description here][1]][1]It looks like this topic is beat to death!   Just bought a vac. home.  Just want to keep pipes from freezing in winter.  Present t stat has R,R,O, black(W label) and G.  Bought Honeywell RTH9585WF smart t stat.  Can I hook up AC and heat? Though only controlling heat remotely.  WITH a 24v transformer?  Option B (approved by H’well) is to switch out t stats each change of seasons.  Doable but a PIA[![enter image description here][2]][2]
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  [3]: https://i.sstatic.net/t083n.jpg