Why does my thermostat have extra wires?

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.

What does the yellow wire coming out of the thermostat do?





The yellow wires underneath your thermostat connect to your compressor. They control your air conditioning system. The yellow wires terminate at your compressor contactor via an air handler.

What color is the yellow wire on a thermostat?

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). You can also refer to the Conductor Color Chart (see Chart 6, thermostat wire).

Why do some thermostats have 4 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.

What do I do with unused C wire?

Quote from the video:
Quote from Youtube video: So what we need to do is turn the power off to our system go down to the heating and cooling. System down where the air exchanger is trace back the thermostat wires and look down there and locate.

Is G wire necessary?





As you mentioned, you don’t usually need a G wire for heating mode, but you do for cooling. In special circumstances a relay could be wired up inside of the air handler to make the fan come on with a call for cooling, but normally it’s the thermostat that makes the connection that makes the fan come in in cooling mode.

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.

How do you identify thermostat wires?

Look for connectors that have labels that are the same as your thermostat. For instance, you might find labels like R, W, G, Y, C or O/B. You should find wires attached to these connectors that are the same color as the wires that connect to your thermostat.

Is RC and C wire the same?

The C and Rc wires are not the same. To install this thermostat you should follow the exact same wiring of the previous thermostat.

How do you wire a 4 wire thermostat?



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

How do you wire a 4 wire to a 2 wire?

The first option is to use the black wire of the 12-3 cable as the hot wire. Connect the black wires of both cables together, and connect the common white wires together. Cap the red wire and leave it untouched in the junction box. Place plastic twist caps on all splices.

How do I connect the 4 wires to my Nest Thermostat?

Quote from the video:
Quote from Youtube video: Now our C in RH in a four wire nest. System are typically basically the same thing they're just inputs for power. So you can have the our terminal. Power going to either RH or RC.

How many wires should a thermostat have?



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 are stranded wires thermostat?

Stranded wires



If your low voltage wires are stranded (each of the wires is a bundle of smaller wires), reinstall your previous thermostat and contact a local pro to have your thermostat wiring replaced or adapted with solid core wire so it can work with Nest thermostats.

How many wires do you need to hook up a Nest thermostat?

Both the Nest E and Nest Gen 3 Thermostats can be installed with 2 wires. The procedure to install the Nest thermostat with 2 wires is the same for both thermostats. Remove the existing thermostat and mark the wires.

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 a 2 wire thermostat?

October 8, 2021. If we put it simply, a 2 wire thermostat is one that has only 2 wires coming out of its backside. As you already know, there are different types of thermostats serving different types of heating/cooling systems.

How do you add a common wire?

Quote from the video:
Quote from Youtube video: Run actual thermostat wire in the all and connect. It to the existing thermostat wire if you've got an extra wire or if you want to fish some new ones in the wall. Not a big deal there.

How do I bypass the C wire on my thermostat?

Quote from the video:
Quote from Youtube video: Add a jumper wire between the Y and G. Terminals. If there's already wires attached just leave them be go ahead and push all the wires in. And close the backplate.

Can I jump R to C wire?



C is a common neutral wire. You can’t jump it from Rh as that is a 24v wire. You need a third wire, C, to return to the unit and hook to the common side of the transformer. For ease of thought, think of R as “hot” and C as “ground”.