If your thermostat doesn’t have a separate connector labeled C and you’re not sure what type of system you have: A brown wire is mostly likely a heat pump wire and should be connected to the O/B connector on the Nest thermostat. If the B wire is blue, it should most likely be connected to the C connector.

What do I do with the brown wire on my thermostat?

Orange- This is used as a cooling relay in the thermostat. Brown- Used for emergencies to relay heat. Yellow- this is part of the cooling apparatus and is used for cooling in the first stage by activating the process of releasing cool air.

What do I do with extra thermostat wires?





Do I need them to install my new thermostat? An extra unused wire in the wall can be used as the C wire for your new thermostat. The extra wire will also need to be connected to the C (common) terminal at the heating and cooling system. This will provide power to your new thermostat.

Can the C wire be brown?

The C, or common wire, provides smart thermostats with continual power. It’s usually blue, but it may also be black, brown or purple. The O or orange wire connects to your heat pump (if applicable).

What is the brown and black wire on a thermostat?

Thermostat Wiring Color Code Chart

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

What is electrical brown wire?

Brown = Live



The brown wire has the function of carrying electricity to the appliance. If the brown wire is live and not connected to the earth or neutral wires there will be a risk of electrocution.

What are the color codes for thermostat wiring?





This is the most typical thermostat wiring style, and it applies to systems that regulate both heat and air conditioning. The wires are typically arranged as follows: red for 24-volt hot, white for heat, yellow for cooling, green for the fan, and blue for common (although the common wire may be a different color).

Why does my thermostat have 6 wires?

If your system has six wires, it’s because it features second-stage heating, second-stage cooling or heat-pump cooling but not all three. The extra wire signals the additional function to come on. If your system has second-stage heating and cooling as well as a heat pump, then the thermostat needs eight wires, not six.

What happens if thermostat is wired wrong?

Potential consequences of improper installation could include: Electric shock. Blowing a circuit breaker. Damaging the thermostat unit, the electrical system or even the AC/furnace unit itself.

What color is the C-wire?

Blue wires



Blue wires are also called “C” wires because they are the Common wire. C wires are necessary for any “smart” thermostat that needs to be connected to a power source 24/7, regardless of your heat pump type.

What is the brown wire on AC unit?

Brown. Like orange, brown-colored wiring activates the heat pump and reversing valve of the AC unit. While orange performs this task during cooling, brown activates these mechanisms while heating.

Is RC and C wire the same?

No the Rc is the red wire. You need 5 wires or more for this to run with all the functions. You can use one of the other wires but you have to drop control of the fan. It will only come on when furnace comes on.

What color wire goes where on a Honeywell thermostat?



Thermostat wires break down wt white wire is heat. Y is yellow and is your compressor. G green is your indoor fan. O is your heat pump and is orange.

Which wire is hot when both are same color?

In most modern fixtures the neutral wire will be white and the hot wire is red or black. In some types of fixtures, both wires will be the same color. In this case, the neutral wire is always identified by some means. In some cases, there will be small writing on the wiring case.

What color wires go on a Nest thermostat?

To wire up your Nest Thermostat, simply: Connect the Red wire from the transformer to either the Rc or Rh terminals (as they are connected internally) Run the White Wire from the furnace to the W terminal. Connect the Yellow Wire from the compressor to the Y Terminal.

How do I connect 4 wires to my Honeywell thermostat?


Quote from Youtube video: That is our 24 volt hot. So that our term the red wire goes to the our terminal. So we just press and slide it in make sure that it locks. And push it all the way then we can go to our green wire.

Why does my thermostat have four wires?



Smart thermostats like Nest and Ecobee thermostats require 4 wire thermostat wiring to function properly. In addition to heating (2 wire thermostats) and C or fan (3 wire thermostats), 4 wire thermostats include the cooling wire, usually in blue or yellow color.

How many wires does a thermostat need?

Most systems today require a minimum of 5 wires when both heating and air conditioning equipment is included in the system. Our pro recommendation is to use 18/8 wire.

What is the W2 wire on a thermostat?

W2 – This is the thermostat terminal used for second stage heat. There are gas furnaces with low fire and high fire and some depend on control from a two-stage heating thermostat with a W2 terminal. Heat Pumps use staging for auxiliary heat and need a W2 terminal.

Is W2 and e wire the same?

W2 is generally called on based on a temperature differential between setpoint and space, outdoor temperature, or run time. W3 – This is just the next stage of heat after W2. E – Is emergency heat, usually just a way to manually drive on what would normally be the secondary form of heat without stage 1 heating.

Should I use W1 or W2?



In a conventional system, W/W1 controls your heating system and, where applicable, W2 controls your heating system’s second stage, which helps warm the home faster. If you have a heat pump system with auxiliary heating, you’ll normally connect the AUX/AUX1 or W2 wire to the ecobee’s W1 terminal.