Asked by: Dayle Yanzhul
home and garden indoor environmental quality

What is the e wire on thermostat?

Last Updated: 2nd April, 2020

Some thermostats have an E wire. The E wire controls emergency heating. Emergency heat is used when the HVAC system is not functioning properly (usually when the compressor is out of service). When you set a thermostat to emergency heat, the system bypasses the compressor and directly accesses the electric heat strip.

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Also to know is, what color is E wire on thermostat?

Thermostat Wiring Color Code Chart

Marking Wire Color Code Description
Marking Wire Color Code Description
C Black/Blue Common of 24 Vac transformer
W White Primary heat cell relay
E Brown Emergency heat relay

Furthermore, what is w1 wire on thermostat? The W or W1 wire controls your heating system. Y or Y1. In most systems, the Y or Y1 wire controls your cooling system. If you have a heat pump, your Y or Y1 wire controls your compressor.

Considering this, where does the e wire go on a Nest thermostat?

1 Answer. The 'E' typically goes to what is called 'emergency heat' which is often the same as and is connected with the 'AUX' (auxiliary heat) used with a heat pump system.

What color is the common wire?

The "common" is the "neutral" or "ground" wire, depending on the type of circuit. In normal US residential wiring, you'll have a black "hot" wire, a white "neutral" or "common" wire, and a green or bare "ground" wire.

Related Question Answers

Yasmany Cinos


What do the colors on thermostat wires mean?

Rh stands for Red-Heat and Rc stands for Red-Cool. If you only have a single red wire the jumper between Rh and Rc are required for some heating and cooling hybrid systems depending on your thermostat. Yellow/Y is the AC compressor. White/W is the Heating element. Green/G runs the fan.

Xuyan Svetoslavova


Is RC the same as C wire?

Though it is a common notion, it may be incorrect to state that the C-wire powers the thermostat. Typically, the wires that give the power supply (usually termed as the 'hot' wires) are marked Rc (for cooling) and Rh (for heating). They give a 24-volt power supply from the HVAC system's control panel.

Encarnita Latini


Is R and Rh the same on a thermostat?

R , Rh , and Rc are all the same, but not. In general terms, the R terminal is where you connect the signal voltage source. This allows current to flow from "into" the R terminal and "out of" the appropriate signal terminal ( W , Y , etc.) of the thermostat.

Fabiana Brigieiro


What happens if you wire a thermostat wrong?

Electric shock. Damaging the thermostat unit, the electrical system or even the AC/furnace unit itself. Dual-fuel systems, a poorly located thermostat, whole-home humidifiers, or incorrect wiring can make the installation of a thermostat a longer, more frustrating, and more complicated process.

Deyan Hedrera


How many wires does a thermostat need?

In the most basic system, this functionality is provided by use of a fan center relay, and the low voltage wiring to the thermostat now will require a minimum of three wires (for heat only units) and four wires (for heat / cool / fan) for control.

Fikri Buchmann


What is the difference between R and RC on a thermostat?

RC is no different and simply means red cooling. The wire is generally red, although there is no color standardization -- but more importantly, the "R" really means that the wire and terminal are hot; it's a live electrical wire. The RC wire connects to the RC terminal, which controls the cooling system.

Yesmin Firmo


What are the different thermostat wires?

G – Fan, usually a green wire. R – 24 VAC usually a red wire (Rc and Rh are discussed later) Y – Compressor, usually a yellow wire. W – Heat, usually a white wire.

Hayar Espinal


Does Nest thermostat E require C wire?

The Nest Thermostat E is designed to work even if your home doesn't have a common (C) wire, but installing a new C wire may be required. If you have a dual fuel system, we strongly recommend professional installation.

Aysha Tudanca


How do I know if my thermostat has AC wire?

It is easy to see if you already have a c-wire connected to your system. Simply remove your current thermostat face from its baseplate and look for the terminal labeled with the letter “c.” If this terminal has a wire attached to it, you have an active “c-wire.”

Cornelis Ravensberger


Will a Nest thermostat work with two wires?

Nest thermostats can work with systems that use Service Light (L) wires. While L wires can't be connected to the Nest thermostat, they don't need them. The Nest thermostat and Nest app will show you system status information without connecting L wires.

Querubin Bagues


What does the blue wire do on a thermostat?

The blue wire, or C-wire, is known as the common wire. It's there to provide power to the thermostat. Older thermostats usually don't have a C-wire because they either don't need power or, if they do, they get it from a battery.

Robustiana Pastoriza


What is common wire?

A common wire is a more general term and simply refers to the 0 Volt wire of a circuit, either electrical or electronic.

Bali Pyjev


What do the letters on thermostat wires mean?

The terminals have letters that refer to functions. R is transformer power, typically 24V AC. Rc is for a separate transformer power from cooling. W is heat, C is common. Y is for cooling.

Stepaniya Zumalde


How do I know if my nest E is compatible?

If you haven't already, go to and enter your thermostat's wires into the compatibility checker. If your system is compatible, you'll get a custom wiring diagram that you will need to install your Nest Thermostat.

Carmella Gauchia


What does w1 and w2 mean on a thermostat?

W1Means first stage heat. Whether that is heat or cool is actually dictated by whether or not the O/B terminal is energized. This is why on many old thermostats you would jumper Y1 and W1 in a heat pump application. W2Means second stage heat.

Atasara Bokmann


What is the difference between y1 and y2 on a thermostat?

In heat pump systems, Y1 controls your compressor, which heats and cools your home. If you have a two-stage compressor, Y2 controls your compressor's second stage, allowing for different levels of heating and cooling. G or G1 controls your HVAC fan.

Malkhaz Pine


What does G mean on a thermostat?

G: The G terminal controls the fan relay and is responsible for turning the blower fan on and off automatically or manually via the thermostat. RC: The RC terminal is the 24-volt cooling power supply. RH: The RH terminal is the 24-volt heating power supply.

Tomasa Bremshey


How does a 2 stage thermostat work?

Two-stage heating means the furnace has two levels of heat output: high for cold winter days and low for milder days. Since the low setting is adequate to meet household heating demands 80% of the time, a two-stage unit runs for longer periods and provides more even heat distribution.

Wilton Santo