How to Install a Honeywell Chronotherm III

Thermostats can be found in just about every home and are used to control the indoor temperature. These days most thermostats are electronic and programmable so after installation they require very little manual adjustments. With a little expertise, the right tools and some patience, you can install your own thermostat which will eliminate the need of a costly repairman. The Chronotherm III Fuel Saver Thermostat is designed for homes that use gas or fuel oil for heating.


Dial thermostats are being replaced by newer electronic versions.
  1. Choose a location with no drafts, hot or cold air from ducts, radiant heat from sun or appliances, or unheated areas like an outside wall behind the thermostat. Install the sub-base about 5 feet above the floor in an area with good air circulation at room temperature.

  2. If you are replacing an existing thermostat, turn off the power at the furnace. Remove existing sub-base from the wall and label each wire color with the letter or number on the wiring terminal to avoid miswiring.

  3. For a new installation, run cable to a hole where you plan to install the thermostat. Pull approximately 3 inches of wire through the opening. Color-coded 18-gauge thermostat cable is recommended. The cable should have one conductor for each wiring terminal.

  4. Remove the thermostat from the sub-base. Mount the sub-base onto the wall. Screws and anchors are provided. With a pencil, mark the two mounting screw positions using the sub-base as a template. Drill the holes for the anchors using a 3/16 inch drill bit. Tap the anchors into the holes. Use plastic anchors if you are mounting to drywall. Thread wires through the opening of the sub-base and mount the sub-base with screws.

  5. Disconnect power before wiring. Straight or conventional wraparound wiring connections are permitted and either is acceptable. Push extra wire back into the hole and seal the hole to prevent extra draft from affecting the thermostat.

  6. Program the time and desired temperature into the thermostat. Install three AAA alkaline batteries into the thermostat to prevent program loss in the event of a power outage.


  • Working with electricity can be dangerous. If you are not experienced with electrical work, it is recommended you get a service technician to install your product. Be sure you disconnect all power to the area you are working in to prevent shock.

About the Author

Currently residing in Washington, D.C, Amanda Kozay has been a personal trainer and fitness professional since 2001. She currently writes a monthly newsletter for her fitness center, which includes exercise and training tips as well as healthy recipes. She holds a master's degree in exercise physiology from Slippery Rock University.