I know serial comms are the new wave. But IMHO, if an installer is installing a heat pump, is 18g/10c REALLY that much more expensive? You have spares in case one is damaged and if the HO wants an upgraded "Smart Stat" there are wires for it. This would have solved the problem if 18g/10c was pulled during the renovation. Sorry, just a rant and a peeve. I'm still mixed between hardwired and serial comms.
Then NEST and my Pro1 are hardwired units. For 2c/3h, they need most of what is in a 18g/10c.