Trane Thermostat Wiring Diagram: 8 Essential Things to Know

Q: What is the common wire on the Trane thermostat?

The common wire on the Trane thermostat is "C". It is also represented by the letter "B". It is usually blue or black and is connected to terminal "B". Its most common uses are to link thermostats and heat pumps.

Q: How do I connect my Trane thermostat?

To connect a Trane thermostat plug Red into "R," White wire into W, Yellow wire into Y, Green wire into G, Black wire is "common", Orange goes into O, and Blue is for B terminals.

Are you planning to replace the wiring of your Trane thermostat and finding it difficult? Worry no more. Today we will explain in detail the Trane thermostat wiring diagram. Read on to learn about how to recognize the wire colors, their importance, the issues if connected wrongly, and more.

Let’s begin!

Table of Contents

An Insight Into Trane Thermostat Wiring Diagram

In the United States, Trane electronic thermostat uses a 24V AC power source. A 110V/24V power transformer supplies it. However, professionals recommend checking the manual and confirming yourself. It consists of:

A white wire connects to terminal W.
A yellow wire goes in the Y terminal.
The green wire goes in terminal G.
The orange wire is connected to terminal O.
A red wire is for the R terminal.
Rh goes into the same terminal as its name, Rh.
RC wire has the same terminal name too, RC.
Blue wire connects to terminal B.

We will discuss the purpose and functions of each in the sections below so stick with us. Meanwhile, have a look at the diagram to understand the wire-terminal connections better.

Trane Thermostat Wiring Diagram — Source: https://www.trane.com/

Trane’s Heat Pump Thermostat Wiring Diagram

The look of Trane’s Heat Pump Thermostat might make you intimidated, but do not worry. Once you learn the basics, you will be an expert yourself, and changing the wires will be easy. Please review the image below and the table to get a gist of it.

Let’s have a look at the details:

Terminal	Connected	Wire Color
R	24V AC Power	Red
W	Heat	White
Y	Cool	Yellow
G	Indoor Fan	Green
C	24V AC Common	Black
O	RV on in Cool	Orange
B	RV on in Heat	Blue
Y2	2nd Stage Cool	Vary
W2	2nd Stage Heating	Vary
E	Emergency Heat	Vary

The table can help you understand where the wires are supposed to be connected. Let’s get into the nitty-gritty details of the heat pump thermostat. Here we go!

R and C terminals

In the table above, you can see that, you must turn on the heat pump thermostat and connect the 24V AC power to the R and C terminals.

Typically, wire R is of Red color while C is Black.
The “common terminal” is C.
The purpose of these two connections is to power the thermostat.

Y and G Terminal

Here is how Y and G terminals come into play:

The signal for the cooling air conditioner is linked to the Y terminal.
When the specified temperature is lower than the ambient temperature, this terminal will signal the need to cool the space.
The indoor fan that moves the air in the room is linked to the G terminal.

Reversing Valve

The following are the purposes of reversing the valve:

To change the refrigerant flow.
It usually runs when the cool mode is on however, there could be times that are shut off during the cool mode.

Therefore, you must review the guidance provided by the manufacturer of the heat pump system you are using.

The O and B Terminal for Reversing Valve

Following is the necessary detail:

O terminal is needed when the thermostat has a reversing valve/Four-way valve. Reminder: Reversing valve runs when the thermostat is in cooling mode.
If it is actuated while the heat mode is operating, you must connect the reversing valve to the B terminal.

Note: Both O and B cannot be connected at the same time. Only one connection can be active at a time in the heat pump thermostat.

Terminals For 2nd Stage Heating and Cooling

Some heat pump thermostats have 2nd stage cooling and heating mode in them. To turn the 2nd stage cooling terminal Y2 is used.

Note: The wire that will be connected to it can vary when it comes to color. In areas that receive heavy winters, the thermostats require a second-stage heating mode is necessary. To make it function, W2 terminal is used.

Emergency Heat

Emergency Heat features can be found in some heat pump thermostats. It uses terminal E. This mode means that you can turn off the heat pump and switch to strip electric heat. That will become the primary source of heating.

However, we do not recommend that you use it a lot as it cost more than the heat pump.

A Sneak Peek into Trane Thermostat Features

Regarding technology, the Trane heat pump thermostat has advanced a lot. When purchasing, you should check out if yours come with the following features:

Low Voltage Alert: It notifies if the incoming voltage is low.
Diagnose Error: It lets you know the problem if your thermostat malfunctions
Auto-Compressor Turn Off: The compressor turns off at 3-minute intervals to prevent short cycling. Short cycling can reduce compressor life.
Set Temperature Timings: You can program the preferred temperature points you need in the daytime and at night time.
Set Temperature Days: You can have different temperature settings for days such as weekends or if you are away on vacation.
Settings Via Smartphone/Remote: You can use an app on your smartphone to monitor the temperature or change it. A thermostat heat pump that has this feature can be costly.

Wiring a Trane Thermostat: Important Instructions to Follow

We have collected important instructions and tips you should know about thermostat wiring. Make sure you have the following in mind:

1. Recognize Your Needs. Then Choose the Thermostat Accordingly

In order to make the correct choice when it comes to Trane thermostats, observe the routines of the habitants of your home:

If there are many people that have different times to stay at home and leave then go for a manual thermostat.
If you have a fixed time to stay and be away from home then a programmable thermostat will be the better option.

2. Connect Wires to Their Designated Terminals

When the wires need changing, take a picture, mark them, or label them by wrapping paper tape around them but most importantly know their color codes. For your reminder:

The red wire is the power cable coming from the transformer’s secondary winding. Connect it to the R terminal.
The Yellow wire is connected to the coil on the cooling contactor. Its terminal is Y.
The white wire is to connect to relay the electric heat or the gas valve.
The green wire goes into the G terminal. It is connected to a fan relay.
The programmable thermostat has a black wire which is a common wire. It is used to connect the common side of the secondary winding of the transformer and C terminal.

3. In the Case of Reversing Valve

If there is a reversing valve, the Trane’s thermostat wiring will be the same with just one exception:

An Orange wire will go to the reversing valve.
It will energize the reversing valve and make the heat pump the primary source of heat.
Here, the white wire is plugged into the heat relay and brings auxiliary heat/emergency heat.

4. Have a Test Run

You should test the unit after done wiring the heat pump thermostat. Make sure to test all the modes. Check heating and cooling. Check the monitor remote or smartphone app till you are satisfied that everything is working as you wish.

Identifying Thermostat Wires

The majority of modern devices follow color-coding patterns, however, in older thermostats, the wiring doesn’t always those. On the HVAC unit, these wires are often identified by a string of letters that describe what each wire is used for. Letters are matched to the wire’s color.

Let us discuss each wire’s functions, colors, and more details below.

The White Wires

Your heating system is connected to your thermostat by the white wire. It links the following to your thermostat:

Furnace
Air handler

In the majority of industry-standard thermostats, the white wire is connected to terminal W. It brings in auxiliary heat.

Note: You can locate more than one white wire if your HVAC system includes several heating phases.

Yellow Wires

Here is how yellow wire plays its part:

The yellow wire is to connect the Y terminal and your compressor. The compressor is turned on and off to regulate your air conditioning system.
The thermostat is connected to the compressor contactor through the air handler using yellow wires.

The Green Wire

The green wire attaches to your thermostat’s terminal G. It links the following to your thermostat:

Furnace
Air handler

This one is easy to spot and remember due to its simple function which is to connect the fan relay to the thermostat.

The Orange Wire

You must know that Orange wire is present only if there is a heat pump.

The orange wire attaches to your thermostat’s terminal O.
In order to switch the valve’s function from hot to cold, it links your thermostat to your external condenser.
Only house owners who have an air-source heat pump will be using the orange wire.
The air-source heat pump is the only part that is connected to the compressor that is outside.

Meanwhile, geothermal heat pump owners can ignore the orange cable.

Red Wires

Following is the detail about Red wire:

The wires are connected to the R terminal. You will notice that these wires are “hot”.
These are used to link the power source and the thermostat. They provide 24-hour volt AC power from your transformer.

The Rc Wire

Here is How Rc wire works:

The Rc wire is hooked to the Rc terminal on your thermostat.
It is used to operate air conditioning systems or dual transformer systems. The dual system refers to the setup that has both a cooling and a heating feature.

The Rh Wire

Here is the detail about Rh wire:

The Rh wire is hooked to the Rh terminal.
Please remember that it is connected to your heating system and not the cooling system on your thermostat.
In case your machine has a dual transformer setup, this wire can be labeled just as ‘R’. It will not be followed with an ‘h’.

The Blue or C Wire

Details about C or Blue wire are the following:

The Blue wire is represented by the letter “B” however, it is also known as “C” as it is a “Common Wire”.
It is necessary for any modern thermostat that requires a 24/7 power source. In this scenario, the type of heat pump does not matter.
Their purpose could vary as well as their color, but the most common usage is attaching thermostats and heat pumps. It is connected to Terminal B.

Importance of Trane Thermostat Wire Color

The importance of the wire colors is huge. It is there to identify each one. It matters because 7-8 wires all have specific functions. Only plug them into their designated terminals.

Note: There are cases where the wire is not connected to the terminal that is supposed to be. The reason most likely would be that wires were swapped. To avoid, this confusion we recommend taking the help of an expert that can be on-site with you.

Effects of Wiring a Trane Thermostat Incorrectly

The consequences of Trane thermostat wiring incorrectly can be severe and dangerous so we would always recommend taking the help of an expert. There are many configurations that you need to remember.

It varies on the HVAC system that you are using that whether it has a digital room thermostat or a simple mechanical one. Hence, you need to have basic knowledge of electrical systems and the tools you are using. Even in these scenarios wiring the thermostat can be tricky.

If an amateur wires the thermostat wiring, the following accidents could occur:

They could possibly blow a circuit breaker.
They can even experience severe eclectic shocks.
They could damage the sensitive wiring
They could damage the thermostat.
They can harm the HVAC unit entirely.
They can test and try the wiring for hours and hours and still be able to figure it out well to fix the issues.

FAQ

What is the common wire on the Trane thermostat?

The common wire on the Trane thermostat is “C”. It is also represented by the letter “B”. It is usually blue or black and is connected to terminal “B”. Its most common uses are to link thermostats and heat pumps.

How do I connect my Trane thermostat?

To connect a Trane thermostat plug Red into “R,” White wire into W, Yellow wire into Y, Green wire into G, Black wire is “common”, Orange goes into O, and Blue is for B terminals.

What are R and W thermostat wires?

R and W thermostat wires: The R terminals are for Red wire. It is used for 24-hour volt AC power from your transformer. The W terminals are for White wire. It links your furnace or air handler to your thermostat.

How many wires does a Trane thermostat have?

The Trane thermostat wires’ numbers can vary, depending on your system. It can be 2-3 wires or 7-8 wires as well.

How do I know which wires are which for the thermostat?

In order to know which wires are which on the thermostat you can learn the color codes. Red wires go into “R.” White wires into W, Yellow wires into Y, Green wires into G, Orange goes into O, and Black or Blue wire are “common.” They are for B terminals.

Conclusion

We have learned so far that learning HVAC unit wires’ color codes and their terminals is the key but one should still go through the manual before performing the wire-changing operation. We hope the Trane Thermostat’s Wiring Diagrams proved useful to you.

What troubles did Trane’s thermostat wiring give you? Let us know in the comments about your HVAC unit and its wiring setup.

Ricky Smalls

I`m a current Law Enforcement Officer working within the Counterterrorism Bureau in New York State. I have been Camping for over 20 years. My styles of camping include tent, car, truck, van, and RV travel trailer. I have a YouTube channel where I teach all types of camping with an entertaining method: https://youtube.com/@TheSmallsRVAdventures