How to Install a Honeywell CT87A Thermostat


Honeywell has been manufacturing energy control devices for over a century, building a reputation for quality and dependability. When installing a new thermostat, choosing a Honeywell CT87A thermostat ensures efficient temperature control, as well as offering one of the most simple thermostats to use. The installation procedure involves only two wires and some basic tools.

Things You'll Need

  • Honeywell CT87A Thermostat
  • Screwdriver
  • Electric drill
  • 3/32-inch drill bit
  • #4 plastic wall anchor
  • 1-inch #4 sheetmetal screws
  • Torpedo level
  • Utility knife
  • Safety pin
  • Shut off electrical power to the furnace at the main breaker panel.

  • Disconnect and remove the old thermostat, if applicable, taking care not to let the thermostat wires slip through the hole in the wall.

  • Separate the Honeywell CT87A thermostat body from its wall plate and large round cover ring.

  • Insert the thermostat wires through the wire opening in the back of the cover ring. Hold the ring against the wall surface at the thermostat location. Make certain the arrow embossed on the ring is pointed upward.

  • Position the thermostat wall plate on top of the cover ring, with its embossed arrow pointed upward. Mark the screw holes at either side of the wall plate.

  • Drill a 3/32 inch hole at each of the two screw holes marked in Step 4, Insert a #4 wall anchor in each hole.

  • Insert the thermostat wires through the wire openings in the back of the cover ring and wall plate. Install the cover ring and wall plate using 1-inch #4 sheetmetal screws into the plastic wall anchors. Use a torpedo level placed on the leveling posts of the wall plate to make certain wall plate and cover ring are level. Tighten the screws using a screwdriver.

  • Strip approximately 3/8 inch wire insulation off of each of the two thermostat wires using a utility knife.

  • Connect the thermostat wires to the terminal screws. Attach the white wire to the terminal labeled "Y" and the red wire to the terminal labeled "R". Wrap the wires clockwise around the screw shaft and tighten using a screwdriver.

  • Pull the thermostat cover off and remove the plastic shipping insert.

  • Set the heat anticipator pointer on the thermostat body to "1.2" using the tip of a safety pin.

  • Install the thermostat body onto the wall plate. Align the three screws at the matching holes in the wall plate. Tighten the screws.

  • Restore electrical power to the furnace at the main breaker panel.

Tips & Warnings

  • If replacing an old thermostat, be aware that many older thermostats contained mercury. Contact your local environmental department for instructions on proper disposal methods and locations.

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