Understanding the Colorful World of Furnace Wiring

5 Mar

Understanding a furnace’s wiring allows you to install a thermostat with ease. At plain sight, it’s a jungle of colored wires connected somewhere in the system, but the confusion brought about by these wires should be minimized, knowing what the colors stand for. Thermostat installation relies on this information to help integrate the controls to the HVAC system.

Today’s thermostats require more wires due to their expanded array of controls. The most basic thermostats, mechanical ones with a tube filled with mercury designed as an automatic control, require a pair of wires to be attached to it. The common colors for this are red-heat and white, but both wires are designed only to provide heat.

Homeowners are slowly phasing out mercury thermostats for more advanced ones, which now adjust for both heating and cooling, but require more wires. Red-cold, yellow, and blue wires are often the colors for cooling. Due to the complexity of advanced thermostats, manuals are packaged with the unit, instructing owners to connect the wires according to the letters.

Letters refer to the terminal designation. Red-hot is Rh, red-cold is Rc, yellow is Y1, blue is Y2, white is W1, and black is W2, among others. Today’s conventional thermostat uses four wires (Rh, Rc, Y, and W). As thermostats evolve in features and performance, more wires may need to be connected.


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: