Best 4 Wire Smart Thermostat In 2023: Complete Guides & Reviews

What is a four-wire thermostat? 

Five 4-wire thermostats have been talked about so far. But what is a four-wire thermostat? A 4-wire thermostat has a cooling wire in addition to the heating wire and C-wire or fan wire needed by 2-wire and 3-wire thermostats, respectively. Most of the time, this wire is blue or yellow.

The color code for the wiring

Thermostats with four wires are often used in standard HVAC systems that have both an air conditioner and a furnace. The conductors are marked with colors:

Rh = Power = Red Wire

White Wire = W = Heating Wire

Cooling Wire = Y = Yellow Wire

Green Wire = G = Fan Wire

Depending on who makes the thermostat wire, blue is sometimes used for the cooling circuit instead of yellow. If there are four wires, the cooling wire is usually the blue one. In a standard 4-wire thermostat, the power for the thermostat and control system comes from the Red wire (R-wire). When it gets to the thermostat and you've chosen the function you want (heating, cooling, or fan), the thermostat will send power to the right system or device. Simply put, the R-wire is where the power comes from, and the other wires are how the HVAC system is controlled. You might be wondering what happens if the wires aren't connected to the terminals correctly. There are times when nothing happens and times when your HVAC system runs by accident. Most of the time, the worst that can happen to your HVAC system is that a fuse will blow. Luckily, fuses don't cost much.

Can you connect four wires to a two-wire thermostat or the other way around?

In principle, yes, you can. It's not hard to switch from a 4-wire thermostat to a 2-wire thermostat or vice versa. Putting in the new thermostat is easy, and you can do it yourself. If you look at the back of the thermostat and see that two wires sticking out, you have a single-pole thermostat. If your thermostat has four wires, it has two poles. What's good about a 4-wire thermostat is that changing the temperature in your home is the same as turning the power on or off to your HVAC system.

The main benefit of a 4-wire system is that the thermostat automatically decides where to send the power to turn on your heating, cooling, or fan system.

What thermostats work with 4 wires?

• Honeywell Home Manual 4 Wire Baseboard/Line Volt Thermostat.

• Dr. Infrared Heater DR-001 Wall Thermostat.

• Honeywell Home Programmable Touchscreen Thermostat.

• Honeywell Line Volt Thermostat.

• Emerson Sensi Wi-Fi Smart Thermostat.

Do all thermostats have 4 wires?

Smart thermostats such as the Nest and Ecobee require a 4-wire thermostat connection to function properly. In addition to the heating wire (2-wire thermostats) and the C or fan wire, 4-wire thermostats have a cooling wire, which is typically blue or yellow in color (3-wire thermostats).

What is the difference between a 2-wire and 4-wire thermostat?

A single pole will have only one set of wires coming out the back. A double pole has four wires rather than two. If your thermostat has more than four wires coming out of it, it is a low-voltage model designed to control a central heating system such as a boiler or furnace.

The best 4-wire smart thermostat is still a viable option for those who prefer not to fiddle with settings menus, as the thermostat's artificial intelligence (AI) handles the majority of the heavy lifting automatically.