How To Wire A Honeywell Thermostat: A Basic 2-Wire Model

A two-wire thermostat is by far the most basic heating system arrangement. If the device only needs two wires, the device can just warm the area.

More cables are necessary if any cooling, such as an air conditioner as well as fan control, is needed. Most people with average home repair abilities can wire a heat-only thermostat.

When dealing with electricity, nevertheless, fundamental safety precautions must be taken.

Here, we have mentioned all the information that you need to know about how to wire a Honeywell thermostat.

Electricity Safety Essentials

Prior to actually starting any action on the Honeywell thermostat, you must review all guidelines and the product’s specifications. If you are unsure about the procedure or have any queries, seek the advice of an expert.

Furthermore, before beginning any job involving electricity, inform individuals around you of your plans. It is for their protection as much as yours.

Before commencing work, disconnect or detach any system components and switch off the electricity to the space at the fuse box panel.

When performing electrical wiring, utilize high-voltage protective gear and instruments with insulated handles wherever feasible.

The Basics of a 2-Wire Thermostat

Honeywell 2-Wire Thermostat

Switch off the electricity to the furnace by flipping the switch on the side of the furnace to the ‘offsetting.

Inability to cut electricity to the furnace preceding wiring the thermostat might lead to a furnace malfunction. Perform all additional safety precautions as mentioned above.

Connect the thermostat wire from the furnace to the spot wherever the Honeywell thermostat will be hung. Put a hole in the wall and run the wire from the furnace through the socket.

The cable will enter the control panel via a specific aperture on the side of the furnace. A rubber wrap should be placed around the hole to prevent the wire from being damaged.

Finally, attach the thermostat wall plate to the frame. Secure the plate using drywall screws.

Color-Coded Thermostats

A red and white wire covered in a brown insulated covering is used in typical two-wire thermostats. Mostly at the Honeywell thermostat and the furnace terminals, peel the red and white wires backward about half an inch.

Plug the white wire to the furnace’s but also Honeywell thermostat’s ‘W’ port. Continue this process with the red wire, attaching it to the ‘R’ terminal both on the furnace as well as the thermostat.

The c wire, also known as the common wire, allows 24 VAC electric currents to flow continuously to the thermostat. However, a usually blue c wire is not present in all thermostat circuits.

For example, a c wire is frequently absent from a two-wire thermostat.

Finishing the Rewiring Task

Fasten the thermostat with the wall plate after connecting the colored lines to the appropriate terminals. Then, switch the furnace again on by flicking the switch on the side of the furnace to the ‘on’ setting.

Adjust the thermostat to ‘heat’ and preset it to the appropriate temperature. If the room temperature falls below the predetermined point, the furnace would activate and start heating the room.

A programmable thermostat might lead to significant savings on heating expenditures. In addition, while you are asleep or have gone out, programmable thermostats automatically reduce the temperature.

Getting to know how to perform your own furnace and Honeywell thermostat repairs could also allow you to stay under budget.

How to Wire a Honeywell Thermostat: CT87N

Honeywell CT87N Thermostat

The Honeywell CT87N thermostat is indeed one of the variants of Honeywell’s renowned analog-dial ‘The Round’ line, frequently installed by homeowners and professionals for dependable, uncomplicated temperature management.

This specific model is in charge of the furnace but also the air conditioner. 

It is designed for systems with 4 to 6 power connections. Wiring the system wires to the thermostat terminals is how you wire a Honeywell CT87N.

Therefore, it is critical to correlate the letter codes on the equipment wires to the corresponding codes on the Honeywell CT87N connectors.

Connecting a Honeywell CT87N Thermostat

Step 1: Switch off the electricity.

Switch off or disconnect the circuit breakers that regulate the electricity to the furnace as well as the air conditioner.

Step 2: Get Rid of the Previous Thermostat

Start by removing the old thermostat’s main cover and circuit. If the thermostat has a mercury thermometer tube or is labeled with a mercury caution, discard it in accordance with the local mercury disposal standards.

Step 3: Unplug the Wires

Put a tiny piece of sticky tape to every wire and label it with the letter of the terminal it is connected to on the base plate of your previous thermostat.

Ignore the color of every wire and merely label them with the letter etched on the previous wall plate. Then, remove each wire one at a time.

Step 4: Take out the Base Plate.

Take off the base plate. Twist the wires well over space in the wall done by the previous thermostat to prevent them from falling behind the wall.

Step 5: Note the location of the mounting holes.

Put the wires through the rectangular slot at the bottom of the fresh Honeywell CT87N thermostat. Connect the thermostat with the wall and, if needed, employ a level to place it.

Specify the locations of both screw mounting holes on the base plate’s edges. Unplug the thermostat, making sure not to allow the wires to slip behind the wall.

Step 6: Bore Screw Holes

Drill holes at the designated locations and press a plastic anchor through every hole with a hammer.

Step 7: Insert Wires Into Thermostat Base

Insert all cables through the cover plate and then into the rectangular slot at the base of the Honeywell thermostat base.

Step 8: Install the Mounting Screws

Align the mounting holes with the screws and tighten each mounted screw into its anchor.

Step 9: Align the wires with the terminal block letters.

Align the letter you wrote on the tape tag of all the other wires to the letter engraved on the left part of the left terminal box or the right-hand side of the right terminal box.

Step 10: Connect the Wires to the Proper Terminals

Plug any ‘R,’ ‘RH,’ ‘4’, or ‘V’ wire into the ‘R’ terminal, any ‘G’ or ‘F’ wire into the ‘G’ terminal, any ‘W,’ ‘W1,’ or ‘H’ wire into the ‘W’ terminal, and any ‘Y,’ ‘Y1,’ or ‘M’ wire into the ‘Y’ terminal.

Before inserting any wire, loosen both terminal screws and disconnect the metal jumper linking them if you have a wire for both the ‘R’ and ‘Rc’ terminals. 

Use the C or X wires at all costs. Do not interconnect the ‘B’ wire if you have a heat pump and both an ‘O’ and ‘B’ wire. All unneeded cables should have their exposed ends covered with adhesive tape and pushed behind the wall.

Step 11: Secure Every Terminal Screw

Unplug the terminal screw, then put the exposed end of the cable securely into the terminal slot and tighten the screw. Make very sure the wire is not coming out of the slot by tugging on it. If it does, redo this procedure.

Step 12: Connect All of the Remaining Wires

Steps 8 and 10 should be repeated for each remaining wire.

Step 13: Connect the Switches

If you have a heat pump or perhaps an electric heating unit, adjust the fan switch in the middle of the thermostat base to “E.” Change the placements of the two-cycle rate controls to match the parameters for the unit.

Step 14: Secure the cover in place with a snap.

Line the thermostat cover’s base tabs well with lugs in the base and slide the cover into position.

Step 15: Switch on the power.

Restart your system and adjust the dial, heating/cooling switch, as well as fan switch as desired.

Thermostat Wiring: How Do You Wire A Thermostat?

We’ll go over the subsequent steps to figure out how to connect a thermostat:

  • To begin, remove the thermostat control panel to expose the various cables. Remember that color-coding might help you learn how the thermostat works.
  • Change the previous Honeywell Smart thermostat with a new model.

Take into account that dealing with wiring might well be harmful to the human body. As a consequence, when working with exposed wires, every time practice the required safety procedures.

Remove the Control Panel from the Thermostat

The basic step in thermostat wiring would be to get proper access to the circuit. Whenever a thermostat is directly mounted on the wall, it is uncomplicated to access the wires; merely disconnect the thermostat’s operating panel beforehand.

Always consider the following points before you proceed: Turn off the thermostat’s main switch.

The major part of the panel board needs to be disassembled by gently pushing them from underneath or even from above. Screws might be present upon certain Honeywell thermostats; simply unscrew them to disclose the wiring.

The base plate and wires projecting from the wall may be located beneath the control panel. The following functions are also featured with the typical Honeywell thermostat:

  • There are 8 wire plugs to the left.
  • There are 8 wire plugs to the right.

Before one remove them, you need to get completely acquainted with the most critical part of any thermostat wiring: Colors as well as wire coding

Color Codes for Thermostat Wiring

There are 16 connectors on the thermostat base. Two-wire, three-wire, and four-wire thermostats do not support any of these features. That’s a rather common occurrence. It’s also worth noting that not all plugs are connected. This is also the usual procedure.

Every thermostat terminal would have its own wire, which is identified by its color.

Thermostat Black Or Blue Wire 

When the C wire is connected to the transformer, the 24V circuit is finished. In contemporary thermostats, a continually looping 24V circuit is employed; in previous ones, the electrical current is passed only if power is required.

The black/blue cable connecting to the C terminal is present in most current smart thermostats.

This cable isn’t usually present in older thermostats; they work on demand, whereas contemporary thermostats activate continuously.

As a consequence, even though the heater or ac is switched off, modern digital thermostats consume power.

Thermostat Red Wire 

The red wire generally referred to as the R wire, would be the power cable. They come from the transformer and provide alternating current power that is available 24 hours a day, seven days a week.

All air conditioning system thermostats are powered by a red wire. Rc or Rh terminals may also be present in thermostat wire; however, these are rare occurrences.

White wire from the thermostat 

White wires are used to supply heat. Thermostats for gas furnaces contain these, but not for air conditioners.

The heating supply, such as a furnace or maybe a heat pump, is connected to the W wires.

The heating element W2 has two stages. As a result, conventional heat pumps with second-stage heating will necessitate the white W2 wire.

Orange for O and Dark Blue for B wire

The reverse lever is kept cooler by the orange thermostat wire, which is marked by the character “O.” The condenser is connected to an orange cable by a few main heat pump manufacturers.

The initial B indicates for reversal of valve heating. Several manufacturers energize the reversing valve whenever the heating mode of heat pumps is initiated.

A dark blue B wire is required for the thermostat terminal.

Thermostat Green Wire

The fan is connected to the green wire. The green or G wire controls the power input to the fan in mini-splits, which feature an inside air handler with a fan.

Yellow Thermostat Wire

To connect to the compressor relay, utilize the Y terminals. The air handler is frequently connected to it. The most common type of cooling at home is Y1, which stands for ordinary or one-stage cooling.

Yellow is the most common color for Y wires with Y1 designations.

Air conditioners that only use second-stage cooling are referred to as Y2.  Especially if you have the below devices would this terminal be required:

  • Compressors two and three
  • Two-stage compressor.

Taking Out The Existing Thermostat

Don’t pull out the old thermostat straight soon if you’re intending to replace it. First and foremost, make certain that the fresh thermostat can be correctly connected.

Color-coding is second nature to HVAC technicians, who can easily remove any Honeywell thermostat, replace it, and reconnect the terminals.

Prior to actually disconnecting the present thermostat, the easiest thing to do would be to:

Take a photograph.

You could have problems linking the connections to the new terminal if you remove the terminals and detach the wires right away. As a result, before continuing, snap a picture of the wiring to the prior thermostat.

Make certain that the wires are properly spaced.

After you’ve captured a picture of the old thermostat, you should disconnect it.

The wires are draped on the thermostat, which keeps them out of the way of the wall. If you detach the thermostat right away, the wire will be lost inside the wall. One of the following choices must be selected:

  • Remove the cords from the wall.
  • Smash the wall to get to the cables.
  • To mitigate these two scenarios, ensure the cables are equally spread. Each wire should be twisted outwards. This is why:
  • The hole in the wall is approximately 22 inches in diameter.
  • The wires are approximately 11 inches long.
  • Moving them apart will provide a cross-sectional area of at least 22 inches, and the wires will be hanging on the wall.
  • Following that, you should be able to safely remove the existing thermostat.

How to Install a New Thermostat

Place the new thermostat in the same area as the old one once it has been removed. The cables you fastened to the wall must pass through the new thermostat’s aperture.

You may now start reconnecting the cables one at a time. In this case, a photograph of the old thermostat is quite helpful. There are two ways to figure out where each additional wire should go:

  • Use the color codes to attach the wires.
  • Power is symbolized by the red cable.
  • A fan is marked with green wire.
  • Heating is indicated by the presence of white wire.
  • Cooling is shown by the blue wire.
  • The capacity to heat 
  • Rc or “resistance to cold.”

To reconnect the wire, try putting it on the proper terminal and tightening the set screws. After that, gently tug a wire to check it is tightly secured.

Swap to a fresh wire after attaching the red wire to R, tightening the screw, and double-checking.

Switch on the mainboard once you’ve reconnected all of the connections to ensure that all is operating properly.

How to wire a basic Two-wire Honeywell Thermostat

Two wires, usually red and white, make up the most elementary thermostat. Two-wire thermostat wiring, which can only be used with furnaces, usually does not require a “C” or “Common” wire. That is indeed why you just need two wires:

  • A red cable delivers power.
  • The white wire is recommended for heating.

A two-wire thermostat has a straightforward wiring scheme. Here’s how to connect a two-wire thermostat step by step:

  • Disconnect the former furnace thermostat’s control panel.
  • Pay attention to where the wires go; normally, red R wire goes to R and white wire goes to Rh or W1. You could also take a picture.
  • The two wires should be removed from the terminals.
  • Remove the control board from the old two-wire thermostat and replace it with the motherboard from the new two-wire thermostat.
  • Replace the control panel after reconnecting the red and white wires and tightening the set screw.
  • You may confirm the two-wire thermostat wiring by turning on the furnace.
  • If the two wires were correctly connected, the new two-wire thermostat should moderate the furnace in the same way that your old two-wire thermostat did.

How to wire Three-Wire Thermostat 

Honeywell 3-wire thermostat

The far most common Honeywell thermostats being used for regulating heaters are three-wire thermostats, which are often found in boilers & heaters. R, G, and W are the most common codes for the three wires found.

The G or green wire, which is normally used for fans, distinguishes a two-wire thermometer from a three-wire thermometer.

The green line acts as a recycled C or Common wire in the 3-wire thermostat circuit. The three wires are shown below:

  • Power is supplied through a red wire.
  • Heating using white wire.
  • As a recycled C wire, use green wire.

The following shows how to wire a three-wire thermostat:

  • Take apart the previous thermostat’s panel.
  • Photograph the three wires. Take note of the colors and the terminals.
  • Remove and secure the cables from the previous thermostat’s circuit. 
  • Replace an existing motherboard and run the wires through the three-wire thermostat.
  • Fasten the terminal screws after properly reconnecting the wires
  • Turn on the control unit and check to see if the boiler linked to the three-wire thermometer is running normally.

How to wire a 4-wire thermostat 

Honeywell 4-Wire Thermostat

Thermostats with four wires offer a little more versatility. However, to work effectively, thermostats require four wires thermostat wiring.

Four-wire thermostats contain the cooling wire, which is commonly blue or yellow in color, in conjunction with the heating wire as well as the C or fan wire.

The terminal codes and labels for the wires in 4 wire thermostats are as follows:

  • Power is supplied through a red cable
  • The heating wire is white.
  • For fans, use green wire.
  • Use a blue or yellow wire for cooling.

This is how to connect a four-wire thermostat by yourself:

  • Remove the control panel to reveal the wires in the original four-wire thermostat.
  • Snap a picture of the cables; you may also identify where everyone goes, but photographing them is much clearer.
  • Remove the motherboard and tighten the cables; if you do not, the four wires will become entangled in the wall.
  • Slide the four wires through the hole after screwing on the new board.
  • Plug the four wires to the proper terminals: red to R, white to W or W1, green to G, and blue or yellow to Y. Tighten each wire to make absolutely sure it’s securely fastened.
  • Switch on the heat pump or just about any HVAC system that is connected to the four-wire thermostat.

How to wire any HVAC System with a 5 Wire Thermostat

5-wire Honeywell Thermostat

A five-wire thermostat is a four-wire thermostat with a C or Common wire added. A 24V C wire connection is required for all contemporary digital thermostats for HVAC equipment to work.

5-wire thermostats seem to be the most flexible thermostats, controlling everything from sophisticated air conditioning systems to heat pumps and heaters.

The following are the colors and terminal codes for the five wires:

  • The electricity is supplied through the red wire.
  • For heating, white wire 
  • Fans have green wiring.
  • Cooling wire 
  • C or Common wire should always be black.

Replacing an old five wire thermostat with a newer one by following these steps:

  • Remove the control panel to reveal the wires in the original five-wire thermostat.
  • You can mark each one, but snapping a photograph is much better.
  • Remove the motherboard and fasten the cables; otherwise, the four wires will go misplaced in the wall.
  • Plug on the fresh motherboard and thread the five cables through the slot.
  • Try to connect the five wires to their respective terminals – red to R, white to W or W1, green to G, blue/yellow to Y, and black to C – and snap them back in place. Tighten every wire to ensure that it is securely fastened.
  • Switch on every device that is linked to the five-wire thermostat and consider using the phone application to see whether everything is working properly.

3 Methods for Wiring any Thermostat

Let’s begin with the most basic way. If the older thermostat is still in place, this will suffice.

If the existing thermostat has already been removed, the procedure becomes a little more complicated, but it is still a do-it-yourself activity.

The thermostat wire should be replaced with the following wire:

Use this strategy even if you’ve never replaced the components of the HVAC system but also want a fresh thermostat.

  • Switch off the furnace power supply.
  • Photograph the old wire that is linked to the various connectors. This will be useful if you lose a note of the terminal to which any cable was attached. You may also utilize the traditional approach of affixing tape markings to the thermostat wires and labeling them with the alphabet of the terminal to which they are connected.
  • Attach a wire from the previous thermostat to the terminal on the fresh thermostat with the corresponding letter. Start by removing and reattaching them once until all of them have been modified.
  • Re-energize the circuit and set the thermostat to heating or cooling.
  • You’re finished if it works, which it should. We suggest resetting the circuit and contacting a local HVAC specialist to finish the task if it does not.

Identify the wire connections in the furnace or air conditioning system by following these steps:

  • If the thermostat has already been disconnected, your task becomes a little more difficult. One of two ways may be effective. This is the most certain strategy.
  • Switch off the furnace or ac unit circuit.
  • Change the thermostat for heating or cooling to check that the device is off. Continue if the system does not switch on.
  • Disconnect the furnace or air conditioning system cover.
  • Find the point where the thermostat’s wiring bundle joins the furnace. It will be made up of three to eight wires of various hues, such as red, white, green, yellow, orange, blue, black, and so on. 
  • A cover over the mainboard may need to be removed to reveal the electrical connections.
  • Snap a photograph of the wiring connection terminals upon that furnace or air conditioning system and make notes which color wire belongs to each lettered terminal after you’ve located them.
  • Keep the furnace cover off until the thermostat is connected.
  • Link the correctly colored wire to the correct port on the thermostat using your photograph and your written details.
  • Re-energize the circuit and set the thermostat to heat or chill.
  • You are done if it functions. You may now replace the cover. We suggest shutting off the circuit and contacting a local HVAC firm to wire the thermostat if it still does not function.

Connect the thermostat using typical wire colors:

However, if the thermostat has already been removed and you do not know which wires are linked to which terminals, this method may work.

It is dependent on whether or not the original installer utilized the usual wire color code to install the thermostat. It is important to note that wiring colors do not have any intrinsic value. 

All of the wires seem to be the same: solid copper wire insulated with colored PVC. The color code was created to help with tasks like the one you’re working on. For example, here’s how to wire a thermostat utilizing color coding and the function of each connector.

  • Connect the red wire to the R terminal (heating/cooling).
  • Connect a green wire to the G terminal (Fan).
  • The white wire should be connected to the W terminal (Heat).
  • The yellow wire should be connected to the Y terminal (AC).
  • Connect the blue wire to the C terminal.
  • Wrap any extra wires around the pack to keep them from getting into contact with exposed wires.

Adding a C Wire to a Thermostat

The C wire provides solid power to the thermostat, allowing it to continuously monitor the interior temperature as well as other climatic factors. The goal is to get the most exact comfort conditions.

Many thermostats operate without a C wire by occasionally drawing electricity from one of the other wires, most often the red wire. 

If the previous thermostat is being removed and no wire is attached to the C terminal, you have a few possibilities. Here’s a rundown of what they are:

  • Replace your thermostat with something which doesn’t require a C wire and accept unsatisfactory results.
  • As the C wire, utilize a spare wire in the bundle. Attach it to the C terminals on the central heating system/air conditioner and also the thermostat. Prior to actually opening the furnace’s lid, make sure to switch off the electricity.
  • The G wire should be used as the C wire. You will no longer be able to operate your fans independently. Connect it to the C terminals of the furnace and the thermostat.
  • Install a thermostat-compatible jumper. The goal is to borrow electricity from another terminal.
  • For setup, contact an HVAC contractor.

Thermostat Wire Replacement

If your replacement HVAC system is of a distinct kind or the wire bundle does not have adequate wires to accommodate the improved performance capacities of the new unit, you will also need to replace the thermostat wire.

The first and most critical step is to obtain the correct type of replacement wire. It is available in bundles of two, three, five, six, or eight wires.

These will be designated 18/2, 18/3, 18/5, and so on as you go shopping for them. When both heating and air conditioning systems are present in the system, typically, systems nowadays require a minimum of five wirings.

The expert advice would be to use 18/8 wire. The difference in pricing is cents/foot, yet having eight wires provides you the most potential for future system upgrades.

Thermostat wire is sold in bundles of 50 to 250 feet and that by the foot at home maintenance retail stores and online merchants. When purchased by the foot, the average cost ranges from 30 cents to 80 cents. It’s less expensive in bundles.

When done with care and diligence, installing thermostat wiring is a simple task:

  • Remove the old thermostat, but keep the wall mount to help protect the drywall while you pull fresh wiring through the gap.
  • Remove about 6″ of the existing thermostat wire first from the wall and secure it with a clasp, large enough to avoid the line from dropping down into the wall when unplugged.
  • Disconnect the existing thermostat’s wires.
  • Wrap electrical tape securely around the overlap of at minimum 4″ of existing and replacement wiring.
  • Drag the wiring bundle toward the furnace. Glitches can be avoided by having a second individual insert wire into the wall.
  • Draw through as much as you need to approach the wire connections on the furnace or air conditioning system, plus an additional foot of wire after the new wire appears. Remove the tape or sever the connection. The wire at the thermostat end should not be severed yet.
  • If the old wire is still attached, remove it from the furnace or air handler.
  • 12″ of insulation should be removed from each wire. Wire strippers cost less and may be found at home repair outlets. If required, add wire connections to each wire. 
  • By using color code and description is given with the thermostat and heating system or air conditioning system, connect the wires to the terminals on the furnace.
  • Attach the clamp to the replacement wire bundle approximately 8″ from the wall, remove the wire bundle, and discard the previous thermostat mount base.
  • Properly slide the old base plate over the clasp, then attach the new base plate to the wall. If you need to remove the clamp for this, hold on to the wire and reattach the clamp after you’re finished.
  • Remove the wires that will be connected to the new thermostat and strip them.
  • Connect the wires to the ports on the thermostat that match the connectors on the furnace or air conditioning system using the wiring diagram. Some thermostat types need the installation of connectors on the wires beforehand.
  • Before actually mounting the thermostat on the base plate, tie leftover wires around the bundle, detach the clamp, and carefully press the bundle into the wall.

Installing Thermostat Wiring: Expert Tips

If you’re moving the thermostat or putting one in new construction, be sure you pick the right spot. Because external walls might be chilly in the winter and warm in the summer, they should be on an inner wall.

This will result in inaccurate readings, an overworked HVAC system, energy wasted, and a household that is too hot in the winter but also too cold in the summer.

The optimal thermostat position is towards the center of your home, on to an interior wall that isn’t impacted by:

  • Sunlight in the face
  • draughty windows or doors
  • A bathroom’s heat or steam
  • Cooking or heat from an appliance
  • Register for heating or cooling

If you don’t have the time or willingness to install a new thermostat and wire yourself, there are pre-qualified local HVAC companies who can handle the job for a reasonable fee.