The Thermostat Wiring Color Code Guide

Step 1 – Turn Off the Electricity First turn off the mains electricity. This step will ensure that none of the wires you touch are carrying any voltage. Step 2 – Identify Your Type of Thermostat Before you proceed, you must know what kind of thermostat you have. If you are not sure, check the number of wires that stick out of the panel. Remove the thermostat, and you should find the wiring attached to the back. If you find less than five wires, you have a traditional heating device, but if there are five or more, you have a heat pump. You should also find a series of letters down the sides of your heating system. All of these letters match with a different wire.

Do I need a c‑wire?

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Heck, now I’m not calling anyone a dummy! Even the most seasoned people who enjoy DIY may come across problems with wiring a thermostat. The main trouble is dealing with those different colored wires, knowing which one does what and if that wasn’t enough, you also have numbers and letters to deal with.

You might need a small flat head screwdriver, depending on how your old thermostat is connected. This might also be the perfect time for me to inform you that by doing this project yourself, you assume all risks associated with it. Different wires from the thermostat control the different functions heat, cool, fan of your HVAC. The most common wires are: This switches on the gas, oil, or electric heat.

That makes things easy, but that might not be the case with your thermostat. Double check to make sure everything is labelled correctly before disconnecting any wires. The wires coming out of the wall should look something like this: Do you have four thermostat wires or five? Notice in the above picture that I have five wires available: Notice that this example has six wires connected: If yours looks like this, label them and skip to Step 5.

The most common example of this would be if you only had R, G, Y, and W wires at your thermostat.

Thermostat Wiring for Dummies

Type CL2, V rating. Blue, Red, Yellow, White, Green. Works with electromechanical relay. Twist the dial and feel the “click” that confirm your changes. Illuminates with the touch of a button or twist of the dial. Features a telephone controller input.

Standards for thermostat wiring colors do not exist except for here and a few other references on the internet. However, these are the most common wiring methods used. Thermostat Wiring Colors Code. Thermostat Terminal Designations Explanations. Two-Stage Furnace Air Conditioner Thermostat Control Problem. By the Way, the S1 and S2.

Also note that it may be against the law, code, or regulations to do this without a permit, or it might void your insurance or warranty. Check your local regulations before continuing. The Nest Thermostat is one of the most popular smart thermostats on the market, mostly thanks to its unique design and easy-to-use user interface.

So if you tend to turn down the heat when you go to bed and turn it back up when you wake up, the Nest will learn this and do it for you, without you having to program it manually. If you see a handful of tiny wires in all sorts of different colors, then you likely have a low-voltage system, but if you see only larger wires that are connected with wire nuts, then you likely have a high-voltage system.

You can also look on the thermostat itself to see how many volts it is. A typical high-voltage thermostat with black and red wires. A typical low-voltage thermostat, with multiple small wires in different colors. Remove Your Current Thermostat Locate your thermostat and turn it off. You might also have to turn off a third breaker for the wire that gives the thermostat power.


A lot of campers come with an old fashioned analog thermostat like the one pictured here. The problem with them is the temperature range before they cycle on or off. Features we all like to have Like many others before us, we decided to swap out our analog thermostat for a nice digital one. Many digital thermostats that will run on batteries will work as a suitable replacement. We decided on a simple, inexpensive model

In this article, I am going to explain the function and wiring of the most common home climate control thermostats. This information is designed to help you understand the function of the thermostat to assist you when installing a new one, or replacing or up-grading an old one.

Your furnace thermostat is an essential part of a home furnace system. The thermostat is responsible for regulating the other systems inside the furnace; it is primarily in charge of maintaining the temperature at the which that you set. If the thermostat is not working properly, you may find that your home is colder or warmer than you would like it to be. Your electric bill may also shock you, as the furnace may be overworked. Read on for a brief and comprehensive guide on how to wire a furnace thermostat.

Step 1 – Prepare the Furnace First, turn off the furnace. Most furnaces have a power switch in the central control or the heating system. If the wire is not already connected to the furnace, connect it to the proper terminal according to your furnace owner’s manual. Run the wire through the furnace covering and into the control panel where the thermostat will be located. If there is not an opening in the control panel, you will need to cut one on your own.

Honeywell Thermostat Wiring Instructions

Home Improvement How to Connect a Programmable Thermostat to a Gas Furnace A programmable thermostat helps reduce your heating costs by automatically turning down your system when you are away. With a programmable thermostat, you can determine what the temperature inside your home should be at set times of day and days of the week. During the times when you’re not at home, your furnace will consume less fuel because it will maintaining a lower temperature.

5 Wire Honeywell Thermostat Wiring. Some programmable thermostats (e.g. Honeywell Prestige wiring requirements) need a minimum of 5 wires, and maybe more depending on what features you want to operate (humidifier, etc).The additional 5th wire will be for common; providing stepped down power from a transformer.. G – Fan (green wire).

The mini splits have the advantage that the refrigerant lines can run up the outside of the house, making them much easier to retrofit. After using the air source heat pumps for two months, I expect these mini splits will approximately halve that. The mini-splits will have an estimated payback of about 13 years, which is not great, but both they and the geothermal system have the added advantage of giving me efficient air conditioning in a home that did not previously have it.

The best you can do with the included remote controller is set them to turn on and off once each during a given 24 hour period, and you have to manually set this up every day to use them that way. Since he told me he would have to figure out how to do the install from the documentation, and I had seen him struggling with the translated-from-Japanese when he was trying to figure out what was wrong with one of the units when it was first installed.

It turns out two of the wires were reversed. There was one point where the documentation was completely unhelpful. Slim Heat Pumps Tools needed:

Adjustable Fan Thermostat Relay and Harness

When I took the front off the current honeywell thermostat, it looks like there are quite a few more wires than what the new thermostat will accept. Do I need a different thermostat? Your current thermostat is designed to allow independent control of the outside heat pump and the inside auxiliary furnace two stage on the heat side.

The two transformers provide the power the thermostat uses to switch on the various relays. The relays in turn switch on the power to the fan and the air conditioner or furnace. Let’s see how this power flows through the thermostat when the air conditioner is running. Power from the air-conditioning.

Smart Home How to install the Nest Learning Thermostat If you’re sold on conserving energy and reducing your bills with Nest, use this guide to install and configure your smart, new thermostat. Although it plays an important part in our comfort and energy bill, it doesn’t get much attention, ignored along with other utilities like the water heater and trash compactor. Most times, we set it, forget it and get on with our lives. But the Nest Learning Thermostat is aiming to change the way we approach heating and cooling with technology and design fit for the gadget lover in a modern home.

And now, three years after its initial launch, the Google-owned company sells a thinner, lower-profile version of its original thermostat. Easy to install and maintain, the Nest packs “learning” features, as it remembers your temperature preferences for times throughout the day and programs itself to create a personalized schedule.

Thermostat, Analog, Standard (12v 6-wire) Heat/Cool Coleman thermostat (7330G3351)

While these are common, they are being phased out of use because they contain mercury. This will be your least expensive option, but it will also come with the fewest features. Like a light switch, this must be turned on and off manually. You must also switch it from heating to cooling and vice versa. While it must still be turned on and off and switched manually, the digital display can make it easier to select a specific temperature.

Features include the ability to set heating and cooling options, and program temperatures according to preset weekday, weekend, and week-long programs.

Thermostat wire comes in various weights. If you have heat and AC, you’ll need 18/5. If you’ve only got heat, 18/3 is sufficient but you may want to run 18/5 anyway for a bit of future-proofing.

When the thermostat stops working, homeowners must replace it in order to keep using their heat and air conditioning. The thermostat controls the flow of the hot or cold air and the temperature inside the house. It also tells the heat pump or air conditioner when to start and stop. Honeywell is a top name in thermostats. The company offers many different types, each with different setup and installation requirements. Before installing a Honeywell thermostat , homeowners need to know what types of thermostats are available, what tools to use, and what steps to take to perform the installation.

Non-Programmable Heat Thermostats Heat-only thermostats only have two wires that connect to the furnace from the electrical box. Where the homeowner installs the new thermostat depends on the location of the old thermostat. Next, remove the old thermostat while making note of the wires connected to it. Use masking tape to label the wires if the need arises.

Remove the thermostat faceplate and connect the positive wire from the furnace to the positive wire from the thermostat using the included connectors. Connect the negative wires in the same fashion. Using the supplied screws, the installer can screw the thermostat to the electrical box. Put the faceplate back onto the thermostat.

Thermostat Wiring