Asked by: Carlos Kerkhoffs
home and garden indoor environmental quality

How do you wire a thermostat light?

Last Updated: 10th May, 2020

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It is really pretty simple. First, take a pigtail (wire with a plug on one end and raw wire on the other) and split the wires enough to reach both the thermostat and the light socket. Second, connect one of the wires to the light socket screw and the other wire to one of the screws on the thermostat.

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Consequently, what color wire goes where on a thermostat?

Here are common uses for wire colors: Blue or Black – C – Common wire, may be unused by your existing thermostat. Enables continuous power flow from the Red wire. Red – R – 24VAC power from the furnace's transformer.

Similarly, how does a thermostat wire work? How Home Thermostats Work

  1. RH - This wire comes from the 24VAC transformer on the heating system.
  2. RC - This wire comes from the 24VAC transformer on the air-conditioning system.
  3. W - This wire comes from the relay that turns on the heating system.
  4. Y - This wire comes from the relay that turns on the cooling system.

Also to know is, 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.

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.

Related Question Answers

Marly Ythier

Professional

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.

Noe Niang

Professional

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.”

Candance Mckeown

Explainer

What are the four wires in a thermostat?

For Four Wires
G – Fan (Green) R – 24 VAC/Rc/R/Rh (Red) Y – Compressor/Air Conditioner (Yellow) W – Heat (White)

Marcial Nottebaum

Explainer

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.

Jacques Grunendahl

Explainer

What wires go where on a thermostat?

HVAC systems with more functions need more wires to communicate to and from the thermostat. The most common is 18/5 (5 strand, 18 gauge). The 5 strands of wire provide enough functions for the modern thermostat. The most common benefit of having 5 conductors is being equipped with a common wire, known as the c wire.

Farha Chergui

Pundit

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.

Xinyao Awelitcheff

Pundit

Are thermostat wires hot?

One of the wires has to be the hot wire coming from the power side of your low voltage transformer. This power wire is usually the Red wire. The color might not be red, but maybe they, the installer, used another color for the hot wire.

Mustafa Brisimitzakis

Pundit

What color wires go where on a thermostat?

Power comes into the thermostat on a wire connected to the transformer, which is usually red, and returns to the transformer on the C-wire, which is usually blue, but it can be black.

Andima Venkatesann

Pundit

Can I use a 4 wire thermostat on a 2 wire system?

Yes, you can connect a four wire thermostat to this setup. Connect the white wires in the same manner as the black wires are connected.

Fredesvinda Lunenburger

Teacher

What does the white wire do on a thermostat?

Wire colors
Older systems and base signals on newer ones
Terminal Probable wire Color Signal
W White Heating call
Y Yellow Cooling call
New signals - for heat pumps and staged systems

Ariane Wilden

Teacher

Where does the brown wire go on a thermostat?

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.

Carolay Chugainov

Teacher

Why does my thermostat only have 2 wires?

If your heating system has only two wires, the job of the thermostat is simple. All it has to do is turn the heat or the cooling on and off. There is also no thermostat blue wire, or common wire, to power the thermostat, so it has to operate on its own, either using batteries or mechanical temperature detection.

Stefanica Valongo

Reviewer

What is RC and RH on a thermostat?

RC and RH. If the air conditioning thermostat has one transformer to power both the heating and cooling system, then the wire from the transformer goes directly to the RC terminal and is called the RC wire. This wire is also known as the RH wire.

Nain Clayton

Reviewer

Where does the black wire go on a thermostat?

The red wire should always come from the hot side of the 24-volt transformer. Additionally, the common (sometimes black) should come from the common side of the transformer. Furthermore, the wire colors on the transformer will be different than the thermostat wires.

Meghan Kreffter

Reviewer

Does thermostat need jumper wire?

Because many thermostats come with a pre-installed thermostat jumper wire that connects these terminals, you only need one red wire, which could be the thermostat Rc wire or the Rh wire. If you don't, you'll need two red wires so you can connect each terminal separately to the system transformer.

Agripino Zafar

Supporter

What do the letters mean on a thermostat?

Y = yellow, g = green, r=red, w = white. Generally the red is your “hot” wire, straight from transformer that supplies constant power to your thermostat, which when each function, ie, cool, or heat is engaged, allows connection between red and whichever wire is called for by the thermostat.

Nikolas El Alaoui

Supporter

What happens if thermostat is in backwards?

If you installed the thermostat backwards, it would probably not open up enough to allow coolant to flow, and the temp gauge would shoot up into the far right range, the engine would overheat, etc. So the overflow tank provides a way for the engine to only have as much coolant as it needs.

Harumi Cuadra

Beginner

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.

Assia Urbani

Beginner

Can you put a thermostat in wrong?

If your thermostat is in the wrong place it can raise your utility costs. Proper thermostat placement can make your heating and cooling more energy efficient while still keeping you comfortable. Here's where to put it and why.