How to Replace a Honeywell 2-Wire Thermostat

Updated February 21, 2017

Honeywell manufactures a wide range of thermostatic controls, from basic and economical to digitally programmable for more complex HVAC systems. For typical residential needs, a Honeywell two-wire thermostat provides dependable, efficient temperature control and simple operation. However, at some point you may find it necessary to replace your Honeywell thermostat. The procedure for replacing a Honeywell two-wire thermostat is simple and can quickly restore dependable operation to your home heating system.

Turn off electric power to the furnace at the primary breaker or fuse panel.

Disconnect and remove the existing thermostat and wall plate. When removing a thermostat, do not allow the wires to fall into the wall.

Remove the Honeywell thermostat from its packaging, if applicable, and separate the thermostat housing from the wall mounting plate.

Position the wall mounting plate against the wall surface at the thermostat location and use a torpedo level to level the plate. Mark the three screw hole centres in the plate on the wall surface. Note: Screw anchors from the old thermostat that align with the new wall mounting plate can be used.

Bore a 3/32-inch hole at each of the screw centre marks, as needed. Insert a No. 4 wall anchor in each drilled hole.

Push the two thermostat wires from the wall through the centre hole in the back of the wall mounting plate and position the plate against the wall, aligned with the anchor holes. Secure the plate into each anchor, using a sheet metal screw.

Attach the two thermostat wires to the wiring terminals. Connect the red thermostat wire to the "R" terminal, and connect the white thermostat wire to the "Y" terminal. Hook the wire clockwise over the terminal screw, and then tighten it using a screwdriver.

Mount the thermostat housing on the wall mounting plate and secure it with the screws provided. Some Honeywell thermostat models use an interlocking wall mount, which secures the thermostat housing by aligning the base tabs and twisting the housing clockwise to lock it into the wall plate.

Turn on the power to the furnace circuit at the primary breaker or fuse panel.


For Honeywell thermostats equipped with a heat anticipator, set the pointer on the anticipator to "1.2" as a typical baseline.


Older thermostats contain mercury. Contact the health department in your area for proper disposal methods and locations.

Things You'll Need

  • Phillips screwdriver
  • Honeywell thermostat
  • Power drill
  • 3/32-inch drill bit
  • Torpedo level
  • No. 6 plastic anchors
  • No. 6 by 1-inch sheet metal screws
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About the Author

Paul Massey has been writing since 2009, drawing on a 35-year career in the construction industry. His experience includes 15 years as a general building contractor specializing in architectural design, custom homes, commercial development and historic renovations.