How To Wire A New Thermostat? An Instruction
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How To Wire A New Thermostat? An Instruction

Is it possible to wire a thermostat yourself? It sure is, but the best strategy is to hire an electrician. Read our quick guide to decide for yourself. For convenience, we discuss a 5-wire thermostat most commonly found in modern homes.

Do you have to shut off the power to change a thermostat?

Shutting off the power before working on a thermostat is a necessary safety precaution that everyone should follow.

Steps To Wire A Thermostat

  • Turn off the furnace power.
  • Remove the control panel and see the colored wires:
  1. Red wire (connects to R, Rh, Rc terminals) - used for 24V power
  2. White wire (connects to W, W1 terminals) - used for heating
  3. Green wire (connects to G terminal) - used for an indoor fan.
  4. Yellow (or blue) wire (connects to Y, Y1, Y2 terminal) - for cooling.
  5. Blue (or black) wire - (connects to C terminal) -an infamous common wire used to close the 24V circuit.
  • Remove the wires
  • Remove the old plate
  • Install the new thermostat
  • Reattach the wires to their respective terminals on a new plate
  • Fix the new terminal gently on the wall and close it
  • Turn the power on

Is RC the same as C wire?

One amateur mistake when wiring a thermostat is thinking that RC and C wires are the same. They are not. RC wire is the red hot 24V power wire that is the part of every terminal. RC terminal stands for cooling power supply.

Now, the C wire is the common wire found in 5-wire thermostats. A common wire ensures continuous power connects the thermostat with the cooling and heating systems, and the electrical circuit is closed. C wires are found in most contemporary thermostats. They are either blue or black,with the former being the most common.

In any case, telling RC wire from C wire is a great test. If you cannot tell the RC wire from the C wire, perhaps it is best no attempt wiring a thermostat yourself.

How do I know if I installed my thermostat correctly? Testing a Thermostat

To test whether a thermostat is working, switch off the furnace, remove the cover of the thermostat, remove the wires from the terminal, twist the removed wires together, and turn the HVAC back on. If the thermostat is defective, the blower will turn on without connecting to the thermostat. You can repeat this action with other wires.

Do you need an electrician to install a thermostat? How much does it cost to have someone install a thermostat?

Theoretically, it is possible to install a thermostat yourself, but this is not the most straightforward DIY project in the way changing the light fixture or setting outdoor lights is. Installing a thermostat requires above average electrical knowledge and an understanding of the thermostat device itself, whether its mechanical, electronic, or electronic programmable one. The latter demands an understanding of how the programs are supposed to work, not just the basic electric knowledge. Installing a thermostat requires a good understanding of the HVAC system in your house as well.

Installing a thermostat yourself may lead to negative consequences, such as electrical shock, interruption of circuit's breaker proper work, irreversible damage to the thermostat unit, and others. In the case of low-voltage 12V and 24V thermostats, death is not a probable outcome, but it is necessary to follow precautions.

! Never install line-voltage thermostats without the required competence, as their voltage (120V or 220V) means that the damage that comes from wrongly installing them is dangerous to life.!

Having an electrician replace a thermostat is the best solution, as it is safe and fast. The electrician will install the thermostat and ensure that your HVAC system works to the best of its ability. The cost of replacing a thermostat in the United States is between $100 and $250, depending on the type of thermostat, the specifications of your electrical project, and the electrician's credentials. 

For a smart thermostat, you will need to hire a person who knows how the system works. A warranty for a new thermostat usually covers an HVAC professional installing it. Hiring a handyperson to install a thermostat is not recommended for smart devices.

Nassau National Cable offers all kinds of thermostat wire at great prices that are safe and easy to install for those literate in HVAC systems.
Vita Chernikhovska profile picture

Author Bio

Vita Chernikhovska

is a dedicated content creator at Nassau National Cable, where she simplifies complex electrical concepts for a broad audience. With over a decade of experience in educational content and five years specializing in wire and cable, her work has been cited by authoritative sources, including the New York Times. Vita's popular series, such as 'What is the amp rating for a cable size' and 'How to wire different switches and appliances,' make technical information accessible. She also interviews industry professionals and contributes regularly to the wire and cable podcast.

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