Tools and Materials
The Importance of A Thermostat
The thermostat is an important device that plays a central role in the home, yet we rarely give it much thought until it breaks. It’s the device that regulates the temperature in our home. It makes sure the heat comes on when it gets too cold and tells the air conditioner to pump out the air when it gets too warm. Without it, we’d be lost. That’s when we realize just how important it is.
When your thermostat is getting up there in years and isn’t doing its job in keeping you comfortable in your home anymore, that’s when you know it’s time for an upgrade.
Thermostats and Industry Standard Wire Colors
In thermostat wiring, the common industry standards use specific colors to control specific functions. The chart above sets out those industry standards.
Always refer to your thermostat’s manual for specific wiring instructions as the colors may differ. Also check to see which wires are connected to which terminals on your existing thermostat.
The Importance of the C-Wire
When you open your existing thermostat, the first thing you need to do is locate the C-wire. The C-wire, also known as the common wire, is most often blue and provides constant power to the thermostat. This wire could also be brown, black or purple. Older thermostats may not have needed this wire, so a previous installer may have moved it out of the way, perhaps behind the wiring plate.
If you can’t locate the C-wire, you’ll need to contact an electrician before you can proceed any further.
How to Wire a Thermostat
While wiring a thermostat is not difficult, it may not be a job that you’re comfortable attempting. If that is the case, contact a professional electrician for installation.
The steps below are for low-voltage (24-volt) systems. Some systems may have high-voltage wiring (two or four thick wires joined with wire connectors; thermostat may indicate 110 VAC (volts alternating current or higher). Many thermostats aren't compatible with this type of wiring and it is a sign that you need to immediately STOP and call a licensed electrician.
Wiring A Thermostat
Safety Precautions to Follow
When dealing with wiring, it’s important to always keep safety top of mind. Follow these steps to ensure the safety of yourself and those around you.
- Turn off the power. Before you begin any work on a thermostat, always turn off the power.
- Avoid placing the thermostat near doors, windows or vents.
- To avoid a system malfunction which could cause a fire, avoid putting thermostat wires into the wrong terminals.
- If any wiring that you see doesn’t look like anything described in this article, contact an electrician.