In this video, This Old House plumbing and heating contractor Richard Trethewey explains how to install a programmable thermostat.
1. Turn off service switch at boiler.
2. Pull off cover from existing thermostat.
3. Unscrew thermostat from its wall-mounted sub-base.
4. Loosen wires connected to thermostat’s sub-base.
5. Remove the old sub-base.
6. Hold sub-base of new thermostat to wall and connect red wire to “R” screw terminal, and white wire to “W” screw terminal.
7. Drill new screw-mounting holes for sub-base.
8. Push plastic wall anchors flush into holes and screw sub-base to wall.
9. Insert batteries into the thermostat and snap on the cover.
10. Turn the service switch back on.
11. Program the desired on/off time and temperature of the thermostat.