Comment by quickthrowman

Thermostats (aka space temperature sensors) can have between two and eight wires. A boiler will usually have three: 24V power, call for heat, and common.

If your boiler has inputs on the terminal block for a thermostat, I would highly recommend buying a wired one, the 24V constant power removes the need for batteries.

If you can provide a link to your boiler’s installation and operations manual, I can tell you.