Instructions to Install a Honeywell RTH221


Your Honeywell RTH221 thermostat is used to control the temperature indoors. Honeywell produces thermostats and other components and systems that control temperature. Currently, its products are in 100 million homes and five million buildings throughout the world. You should always follow the manufacturer's instructions during installation. Improper installation could keep the unit from functioning properly and could void the warranty for the product. It can even create a fire hazard if electrical components are involved.

Things You'll Need

  • Pencil
  • Screwdriver
  • Drill
  • Electrical tape
  • Wire labels


  • Turn the power off. Whether your new thermostat is for a heating or cooling system, turn the main power off first.

  • Remove the old thermostat, but leave the wires and wall plate in place.

  • Use the terminal screw labels to identify the wires. Use electrical tape to wrap the ends of any wires that were not attached to your old thermostat and any wires marked "C" or "C1," which you will not use. Disregard the wire colors and label them according to the terminal screw labels. After all of the wires are labeled, disconnect them and remove the wall plate. You can wrap the wires around a pencil so that they don't fall through the wall.

  • Mount the new wall plate by first loosening the screw at the bottom of your thermostat.The screw cannot be entirely removed from the thermostat. Separate the wall plate and thermostat. Put the wall plate against the wall and use a pencil to mark the holes. To install the wall anchors, drill holes at the marked positions and insert. Slide the wires through the large opening at the bottom center of the wall plate. Use the mounting screws to secure the wall plate.

  • Loosen the terminal screws with a screwdriver and insert the wires, and then tighten the screws. Push any unused wires into the wall opening. Match the wires with the terminals having the same letters.

  • Insert two AAA batteries in the back of the thermostat. Align the brackets on the top of the thermostat with the slots on the top of the wall plate and push it in. Tighten the screw at the bottom of the thermostat.

  • Turn the power back on.

Tips & Warnings

  • Read the directions before getting started and again during installation.
  • Failing to turn the main power off can result in electrocution.

Related Searches


  • Photo Credit Spencer Platt/Getty Images News/Getty Images
Promoted By Zergnet



You May Also Like

Related Searches

Check It Out

22 DIY Ways to Update Your Home on a Small Budget

Is DIY in your DNA? Become part of our maker community.
Submit Your Work!