Thermostats are the ultimate control hubs for HVAC devices such As furnaces and air conditioners. Thermostat wiring is a reusable skill to know if you have to replace an old thermoregulator or just check if something is unethical with the new thermostat. With a bit help, you can learn how to install a thermoregulator along your own.

LearnMetrics has designed this template as that little help. We will pass over everything you need to know around thermoregulator wiring; including where does each color wire goes.

Obviously, in that location are many a different kinds of thermostats out there. 100% of guidelines will not work for 100% of thermostats. On that point are, later whol, numerous different types of thermostats with different wiring out there: Honeywell thermostat wiring, nest wiring, old thermostats, and so forth.

We will cover the well-nig democratic thermoregulator wirings for 2 electrify, 3 electrify, 4 telegram, and 5 wire thermostats. At every stage, we will show out what 2 wire or 5 telegraph thermostats are wont to conducting wire, for example, to get a bigger picture of where those discolor wires go and how they enable the functions of strain conditioners and furnaces.

In totally cases, we volition use this basic Honeywell thermostat for source:

honeywell thermostat wiring
This is a standard Honeywell thermoregulator; perfect for learning the ins and outs of thermostat wiring. The protocols apply to Honeywell thermoregulator wiring as well as for other thermoregulator wiring.

We will also try to address all the shared questions regarding thermostat wiring, so much as:

"What color wire goes where on a thermostat?" (Check the diagram below)

"How galore wires does a thermoregulator need?" (At the least 2)

"What is R and RC on the thermostat?" (Color coding diagram beneath)

"What is the black telegraph for on a thermostat?"

"What if there is nary C wire for the thermostat?" (Older thermostat; you buttocks exit it without or add it)

Let's take a systematic and practical approach here. We will watch this general order to learn how to wire a thermostat:

  1. Remove the thermoregulator instrument panel, and expose the colored wires.
  2. We will learn what each color wire means. Agreement semblance steganography will give you a good understanding of how the thermostat actually functions.
  3. Replacing the old thermostat with a new one.

An important note: Keep in idea that dealing with electrical circuits can embody harmful to yourself. That's why always follow the appropriate safety measures when working happening live electrical circuits. For more data around the wires and their ampacity, consult the AWG gauge chart with wire sizes for specific amps present.

Let's part with right off with exposing the color wires:

Removing The Thermostat's Control board (Acquiring To The People of colour Wires)

The initiative in thermostat wiring is in reality getting to the wires. You probably have your thermostat mounted on the wall. Exposing the wires is unproblematic; IT starts with removing the thermostat's instrument panel.

Before you start: Turn the power switch to the device's thermostat is connected to off.

Most command panels can be removed just by nudging information technology from below or above a morsel. Much Honeywell thermostats tail end have some screws as well; just unscrew them to expose the telegraph terminals.

Beneath the control board, you will find the base and the wires sticking knocked out of the wall. With the basic Honeywell thermostat, you will find:

  • 8 wire sockets to the left.
  • 8 telegraph sockets to the right.

Before we take the flathead lie with to unscrew these, let's first acquaint ourselves with the crucial part of any thermostat wiring: Wire codes and colors.

Here's where the thermostat wires go:

Thermostat Wiring Color Codes

As you can see connected the thermostat base, you have 16 sockets, with letters C, R, W1, W2, O/B, G, Y1, Y2, Bk, 2x RS, 2x ODT, AUX Nobelium, AUX C, and AUX Old North State. With 2 cable, 3 wire, and 4 wire thermostats you don't have completely of these. That's pattern. You might also notice that every last sockets don't wire in them. That's classical A well.

For each of these thermoregulator terminals, thither is a designated wire, characterized by a color:

thermostat terminals with codes and color wires
Thermostat consists of 16 sockets with codes (C, R, W1, W2, O/B, G, Y1, Y2, BK, 2x RS, 2x ODT, AUX NO, AUX C, and AUX North Carolina) and selected color wires.

If your thermostat doesn't attend exactly like this, or even anything like this, don't worry. We just need to get a grip of what each distort wire is and what information technology does.

Let's look at all of these wires successively:

Thermoregulator Black Beaver State Grim Wire ("C" Wire)

The black electrify or blue wire (either color is used) is the C – "Grassroots" wire. What does the C wire do? C wire is coupled to the transformer and completes the 24V exciting electrical circuit. Newer thermostats have a ceaselessly whorled 24V racing circuit; in older models, the loop is completed only when the king is needed (when you turn the AC on, for example).

More often than not, the black or blue telegraph connected to the C terminal is found in the newer "smart" thermostats. The older thermostats may not have the "C" wire; they function on-demand while the New ones function day in and day out (ceaselessly 24/7).

That's why the newer digital thermostats consume energy symmetric when the furnace or air conditioner is not running game.

Thermostat Red River Conducting wire ("R" operating room "Rc" Wire)

Red electrify or "R" telegraph is the power wire. They originate in the transformer (air conditioners; in the air animal trainer) and provide the 24-hour volt Ac power.

All air conditioner thermostats let a red wire for power. You may also have Rc or Rh terminals for dual transformer systems; these are special cases in thermostat wiring.

Thermostat White Wire ("W1" or "W2" Wire)

White wires are for heating system. You will find them in natural gas furnace thermostats, for example, just won't find them in aerial conditioner thermostats.

W wires proceed directly to the source of heating; that may be a furnace (gas, electric, oil, you name it) surgery heat energy pumps (mini-split heat pumps enclosed).

W2 is designated for two-stage heating. Most heat pumps include forward-stage heating system and require the whitened W2 wire.

Orange River Wire For O And Dark Blue Conducting wire For B ("O/B" Wire)

"O" or the orange tree thermostat wire is for reverse valve chilling. Most bigger heat pump manufacturers like Trane, Goodman, Lennox, so on own the orange wire that goes to the condenser (settled in the open-air unit of heat pumps).

"B" is for reversing valve heating. Some producers like Rheem energizes the reversing valve when the heating mode is on in ignite pumps. A navy blue "B" telegraph is needed for the t-stat last.

Thermostat Fleeceable Wire ("G" Wire)

Green wire is for the fan. Mini-splits have an indoor air manager with a fan; the power input that goes into the fan is regulated by the green or "G" wire.

Chromatic Thermoregulator Wire ("Y1" And "Y2" Wire)

Y terminals are for the connection to the compressor electrical relay. It most often wires to the air handler (interior cut-system whole). Y1 is for ordinary or one-stage cooling; this is what most of USA have at home. Y wire with "Y1" code is usually yellow-colored.

"Y2" is only for air conditioners with sec-stage chilling. This terminal is only required if you have:

  • 2 compressor.
  • Two-stage compressor.

Other Wires (Atomic number 97, RS1, RS2, ODT1, ODT2, AUX Nary, AUX C, AUX NC)

Other terminals that rarely get used the least bit the ones on the redress side of the thermoregulator. In the future, we plan to create a ramify article details that the specific function all of them have.

Do keep in mind that with so many distinct thermostats, each telegram code can have a different color wire. "O" conducting wire, for lesson, is not necessarily always orange. If a technician that installed your thermostat used a varied color, you might have a job reconnecting the wires. That's why this next section is so important:

Removing The Old Thermoregulator (Take Photo)

If you're planning to replace the old thermostat, don't immediately get rid of the old thermostat. Archetypal of whol, make a point you testament be able to aright wire the new thermostat.

HVAC technicians know the color-coding by heart; they can just remove any Honeywell thermostat, replace it with the red-hot same and reconnect the terminals.

If you are DIY thermoregulator wiring, here's the easiest thing to do before removing the old thermostat:

Use up a picture.

If you unscrew the terminals and remove the wires right by, you may have got problems reconnecting the wires to the new terminal. Make certain you have a picture of how the wiring to the old thermostat looks comparable before continuing.

Make a point To Spead The Wires (You Preceptor't Want To Lose Them In The Wall)

When you deliver taken the pic of the old thermostat, you lavatory remove it. But do atomic number 4 careful:

The thermostat holds the wires out of the fence in; the wires are suspended along the thermostat. If you remove the thermostat satisfactory absent, the wires will be lost inside the wall. You will ingest to either:

  • Fish the wires proscribed of the wall.
  • Smash the wall to be competent to scope the wires.

To prevent these two scenarios, build surely to spread the wires. Occupy each telegraph and bend it outwards. Here's the logic behind this:

  • Gob in the wall is about 2×2 inches.
  • Wires themselves are about 1×1 inches.
  • Spreading them apart will create at least a 2×2 inch crosssection, and the wires will be suspending on the bulwark (instead of on the thermostat).

When you have done that, you bathroom safely remove the old thermostat.

Installing A New-sprung Thermostat (Reconnecting Wire By Wire)

After you remove the old thermoregulator, take the new thermostat are put it in the demand like billet atomic number 3 the old thermostat. The wires you receive fixed along the wall feature to be pushed through the gob in the new thermostat.

At present you start reconnecting the wire by telegram. Having a photo of the rusty thermoregulator is very helpful here. There are two shipway of how to know where each telegram goes:

  1. Utilisation the photo and reconnect the wires consequently.
  2. Expend the coloring codes and reconnect the wires.

If you are going away color codes, you seat check what each wire means in the section above. Here's a quick primary summary:

  • Red wire: Mightiness (24V input in nearly cases).
  • Green wire: Lover.
  • White wire: Warming.
  • Blue electrify: Cooling.
  • Rh: Heating power.
  • Rc: Cooling system major power.

To reconnect the wire, simply put the wire on the right terminal and stiffen down the set screw. Pull a wire a second to make sure the wire is properly fixed.

Example: Reconnect the red wire to R, tighten the gaoler, check, and move to the new wire.

After you have reconnected all the wires, put on the control board, and check if everything is fine.

Now that we get it on the basics of how to decent cable a thermoregulator and the basics of color-coding, let's attend at how to wire 2, 3, 4, and 5 wire thermostats in piecemeal guides:

2 Wire Thermostat Wiring (Furnaces)

The most basic thermostat has 2 wires; usually a red and a white wire. Ii wire thermostat wiring is used for furnaces only and usually doesn't want a "C" or "Common" wire. That's wherefore we solely need two wires:

  1. Red wire for power (24h).
  2. White wire for heating.

Wiring a 2 telegram thermostat is beautiful unambiguous.

Here the in small stages of how to DIY 2 wire thermostat wiring:

  1. Remove the control board of the old furnace thermostat.
  2. Take a note of where the wires get on; unremarkably, red R telegraph will go to R, and flannel electrify will attend Rh or W1. You can also convey a exposure.
  3. Unscrew the two wires from the terminals.
  4. Remove the motherboard of the old 2 wire thermostat and put down the new 2 telegram thermostat in its berth.
  5. Reconnect the Red and white wire, tighten blue the put down screw, and put the control panel back on.
  6. Test the 2 wire thermostat wiring by turning the furnace happening.

If you have properly reconnected the 2 wires, the new 2 wire thermostat should control the furnace in the same way your nonagenarian 2 wire thermostat did.

3 Conducting wire Thermostat Wiring (Boilers, Heaters)

3 wire thermostats are most usually used to curb the heaters; boilers and hot water heaters in particular. The 3 wires you will find usually have codes R, G, and W.

The difference of opinion between 2 wire and 3 telegraph thermometer is the "G" or unripened wire that is usually used for fans. In the 3 wire thermoregulator wiring, the green wire serves as a repurposed C or "Common" wire. Here are the 3 wires:

  1. Reddened telegraph for business leader (24V).
  2. White wire for heating (connected to W OR W1 terminal).
  3. Green wire as a repurposed C wire.

Hither is how to wire a 3 wire thermostat:

  1. Murder the control panel of the aged thermostat.
  2. Take a scene of the 3 wires. Note the colourize – red, lily-white, and green – and the terminals – R, W or W1, G.
  3. Remove the motherboard of the early thermostat completely, and secure the wires. You don't want them to pelt bass inside the wall.
  4. Assign the new motherboard in the place of the aged indefinite, and pull the wires through and through the 3 conducting wire thermostat.
  5. Correctly reconnect the wires – red to R, white to W Oregon W1, green to G – and stiffen the terminal screws.
  6. Fictive the instrument panel, and test if your boiler or hot water heater connected to the 3 wire thermometer functions properly.

Knowing how to telegram a 3 conducting wire thermostat is fairly promiscuous compared to 4 and 5 wire thermostats:

4 Wire Thermostat Wiring (Heat Pumps, HVAC)

4 wire thermostats have a little more flexibility. Smarting thermostats like Cuddle and Ecobee thermostats postulate 4 wire thermoregulator wiring to function properly.

In addition to heating (2 wire thermostats) and C or fan (3 wire thermostats), 4 wire thermostats include the chilling telegram, usually in blue operating room yellow color. Here are the wires in 4 wire thermostats with end codes and color codes:

  1. Red-faced wire for power (24V).
  2. White cable for heating (connected to W surgery W1 period).
  3. Green wire for fans.
  4. Cheerless or yellow wire for cooling (machine-accessible to Y).

These thermostats are typical for heat pumps: HVAC devices that can aplomb and heat. To produce the airflow, a fan is needed (green wire).

Here is how you can wire a 4 wire thermoregulator yourself:

  1. Take the control panel off and expose the wires in the old 4 telegram thermostat.
  2. Submit a photo of the wires; you can likewise label where each one goes, but winning a photo is much easier.
  3. Take off the motherboard and strong the wires; if you preceptor't carry them, the four wires will get lost in the wall.
  4. Screw on the new motherboard, and pull the 4 wires through the hole.
  5. Reconnect the 4 wires to the appropriate terminals – chromatic to R, white to W or W1, green to G, and blue or yellow to Y – and screw them in place. Pull each conducting wire to throw sure that it's unchangeable in place.
  6. Turn on the heat pump operating theater any other HVAC device that connects to the 4 wire thermoregulator.

Let's look into one of the most common thermostats. Here is the Honeywell 5 wire thermostat standard wiring:

5 Wire Thermostat Wiring (Any HVAC Gimmick – Air Conditioners, Heat Pumps, Furnaces, etc.)

5 wire thermostat is basically a 4 wire thermoregulator with a "C" or "Common" wire. The newer digital thermostats for HVAC devices all require a 24V C wire connective to social function. 5 wire thermostats are the nigh versatile thermostat; they control anything from smart air conditioners, heating plant pumps, furnaces, and so connected.

Hera are the 5 wire colors and terminals codes:

  1. Colored wire for exponent (24V).
  2. White wire for heating (connected to W or W1 terminal).
  3. Green conducting wire for fans.
  4. Blue OR yellow conducting wire for cooling (connected to Y).
  5. Black wire for "C" Oregon "Common" wire.

Here is how a bugged 5 wire thermostat looks like:

wired 5 wire thermostat with black, red, white, green and yellow wire

Countenance's take how to replace an old 5 wire thermostat with a new one:

  1. Take the instrument panel off and expose the wires in the old 5 cable thermostat.
  2. Take a exposure of the wires; you can also judge where each one goes, but taking a photograph is much easier.
  3. Take off the motherboard and sure the wires; if you get into't hold them, the foursome wires will get bemused in the wall.
  4. Screw on the new motherboard, and pull the 5 wires through the hole.
  5. Reconnect the 5 wires to the earmark terminals – red to R, white to W or W1, chromatic to G, and drab or unhealthy to Y, black to C – and screw them in place. Pull apiece wire to make reliable that IT's stationary in situ.
  6. Turn on whatsoever smart device that connects to the 5 wire thermostat, and try to usance the smartphone app or remote to check if everything works as it should.

These are the fundamental principle of thermostat wiring. If you have just a bit of technical skills, you will in all probability be more able to DIY thermostat replacement.

Using 3 Wire to Turn on Furnace Fan

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