What are reliable paths to install smart thermostats on two-wire (heat-only) systems—C-wire adapters, power-stealing models, or control relays—without nuisance lockouts?
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Okay, so if you’re a DIY type who knows the basics, try a C-wire adapter or a thermostat with a power extender kit (like Ecobee). Power-stealing can work, but might cause problems now and then. If you want something super reliable and pro-level, go with a relay and transformer or just run a fresh wire.
Reliable options include adding a C-wire via a thermostat wiring kit or running a new conductor, using a dedicated 24 V transformer with a relay interface, or selecting a smart thermostat designed for two-wire power-stealing that’s proven with your furnace model. Proper sizing and wiring avoid nuisance lockouts or short-cycling.