Even the most seasoned people who enjoy DIY may come across problems with wiring a thermostat. I will explain that in a little more detail further down this page. What I would like you to know is the information detailed below is based on the industry standard, yet not all thermostats will work this way simply because letters and numbers are used as well as color. So, this is what you might expect to see in terms of colored wires and what they mean:. AND it has been recorded by a professional in the industry. Thermostat Center is supported by our readers.
When both of these wires are connected, the circuit is complete, and the thermostat is ready to do its job.
The two wires coming out of your wall should be red and white, but they may not be, and if not, you may have to check the control panel on the appliance to determine which wire is which. The control panel has the same terminal designations as the thermostat.
Just note the colors of the wires on the R and W terminals and connect those wires to the R and W terminals of the thermostat. If you're controlling an appliance without terminal designations, such as a furnace, consult the furnace wiring diagram to identify the terminals.
You're unlikely to get a life-threatening shock when handling volt wires, but it's safer to get no shock at all.
Turn off the breaker controlling the furnace or air conditioner before wiring the thermostat.
When connecting wires to the terminal screws, trim off excess wire that could contact other terminals. If the wires touch and make a short circuit, the thermostat won't work.
How To Easily Install And Replace A Honeywell Thermostat
If your furnace or air conditioner runs all the time, the wire connections are the first thing to check. Chris Deziel is a contractor, builder and general fix-it pro who has been active in the construction trades for 40 years. Of course though, you should check that the wires in your HVAC system match up with their expected functions. The red wire R, RC, RH connects the high side of the output of the control transformer to the t-stat.
Also referred to as the C wire, this wire connects the low side of the output of the low voltage power to the t-stat. Note that in our case, we had to use the green wire for C, as discussed below, because there were only four wires coming from the furnace to the t-stat which included no blue, brown, or black wire. So we decided that we could do without the fan switching function that the G wire normally provides, in favor of the remotely programmable capabilities of a Wi-Fi smart t-stat that must have a C wire in order to function.
Later on though, we hope to run new t-stat wire, that has more conductors, so we can get the C as well as the G wires. The wire colors for these extra terminals aren't specified.
How to Wire a Honeywell Thermostat with 4 Wires In the installations we've worked with, the most common wire color code guide for a four wire t-stat are as follows. Of course though, you should check that the wires in your HVAC system match up with their expected functions. Aug 24, In standard thermostat wiring, the blue wire connects to the common terminal on the thermostat, making it the C-wire. In this configuration, the blue wire acts as the return wire between the 24V transformer in the heating/cooling system control panel and the thermostat. The red wire is hot. Sep 05, The wiring for your Honeywell thermostat depends on the functions of your heating and cooling system. You'll probably see a thermostat jumper wire connecting the Rc and Rh terminals. It's there so you can supply power to the heating and cooling switches with a .
Other thermostats have fewer wires. Again referring to the Honeywell thermostat ct31a wiring diagram, you can see it requires only two wires, R and W. It doesn't control cooling and, because it's a mechanical thermostat, it doesn't need power for internal functions, so it has no C wire.
If you're looking for a Honeywell two-wire thermostat, you can't do much better than the Honeywell T87 series. The Honeywell T87 is the standard round thermostat you find in many older homes, although some newer models have a backlit LED screen instead of . The Honeywell RTHB is a programmable version of the Honeywell RTH thermostat series. When replacing an existing thermostat, simply note the terminals to which the wires are attached and attach them to the same terminals. If it's a new installation, you may have to identify the wires first.
If your system has both heating and cooling functions, you'll need to connect both the Rc and Rh terminals with a red 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.
This means that you do have a c-wire, you just need to find the end of the lead near your thermostat. If you can't find the c-wire or need help with the difference between a 2-wire thermostat and a 4-wire thermostat, call a professional electrician. Alternately, look for thermostats that specifically say they do not require a c-wire for. You may also have up to two black wires as well but these are used for various heating systems in the North or for outdoor purposes, so for most of you these won't need any attention. If you're still a little confused (and I can understand why you would be), I have added a thermostat wiring made simple video for you to look at which isn't. How to Hook Up a Home Thermostat - If you need to install a new thermostat then you have found the right place to learn. Below we will describe to you how to hook up a new digital thermostat. Whether the old thermostat is bad or not if you simply want to replace your old one and hook up a new one.
If this jumper wire isn't present, you can install one yourself. If you don't, you'll need two red wires so you can connect each terminal separately to the system transformer.
When installing a thermostat, many people - even HVAC pros - don't always pay attention to wire colors, so you can't assume that the colored wires sticking out of your wall perform their standardized functions. The best way to identify the wires is to look on your system control panel. It has the same terminal designations as the thermostat does, and you can simply note the color of the wire attached to each terminal.
If you're replacing an existing thermostat, note the color of the wire attached to each terminal before you disconnect it, and connect the wires to your new Honeywell thermostat in the same way. Chris Deziel is a contractor, builder and general fix-it pro who has been active in the construction trades for 40 years.