How-to guide

Smart Thermostat Settings to Check After Installing

Updated 2026-09-30

Wiring is only half of a thermostat install. The setup questions in the app decide which wire does what, how long equipment runs and when backup heat is allowed. Most problems reported as "the new thermostat doesn’t work" are settings. Here are the ones worth checking, in the order most apps ask for them. Names differ a little between Nest, ecobee, Honeywell Home and Amazon, but they all have these settings.

1. Equipment type

Choose conventional (furnace or boiler, with or without AC) or heat pump. On a heat pump, Y runs the compressor for both heating and cooling, and W becomes auxiliary heat. If this is wrong, the thermostat sends heat calls down the wrong wire.

2. O/B reversing valve

Heat pumps only. O is used by most brands; B by Rheem and Ruud. If cooling blows warm air, flip this setting. See O/B explained.

3. Stages

If you connected Y2 or W2, confirm the thermostat detected the second stage. Many thermostats let you choose when it steps up: after a set time, or when the temperature is far from the target. Letting the first stage run longer is usually more efficient and quieter.

4. Aux heat and dual fuel

• Set the aux heat type (electric strips or a furnace).
• An aux heat lockout (or "aux heat max outdoor temperature") keeps expensive strip heat off above a temperature you choose. Many homes use something in the range of 35 to 45 °F; a technician can tell you your heat pump’s balance point.
• For dual fuel, set a compressor lockout temperature below which the furnace takes over, so both never run together.

5. Compressor protection

Every major brand includes a minimum off time for the compressor, usually around five minutes. Leave it on. It stops the compressor restarting against high pressure after a short off cycle, which is hard on it.

6. Temperature differential

This is how far the room can drift before the thermostat starts heating or cooling (also called swing, threshold or cycle rate). A very small value gives more even temperatures but shorter, more frequent cycles. If your system starts and stops often, widen it a little.

7. Fan settings

• Fan mode: Auto runs the fan only with heating or cooling. On runs it constantly.
• Fan circulation: some thermostats can run the fan a set number of minutes per hour to even out temperatures between rooms.
• Heat dissipation / fan overrun: runs the fan briefly after heating to push out the remaining warm air.

8. Schedules and learning

A schedule saves energy when the setback is large enough to matter and long enough, such as overnight or while you are at work. For heat pumps, use the thermostat’s smart recovery or "heat pump balance" features so it doesn’t call aux heat to recover from a big setback in the morning.

9. Test every mode

Finish with a short test: heat, cool, fan on and, on heat pumps, emergency heat. Each should start within a few minutes. If something doesn’t, use our troubleshooting checklist.