Thermostat Wire

Thermostat wire is the low‑voltage HVAC control cable that links thermostats to furnaces, air handlers, heat pumps, boilers, humidifiers, and zone valves. Chosen correctly, it delivers reliable 24‑volt signaling, clean installs, and fewer callbacks. Most jobs use 18 AWG solid copper in 2 to 8 conductors, with 18/2 for heat‑only, 18/4 for standard heat/cool with fan, and 18/5 or more for smart thermostats that need a C‑wire or extra accessories.

Look for UL-listed CL2 or CL3 ratings to meet NEC Article 725, with CMR (riser) or CMP (plenum) jackets for ducts and air returns. For basements and outdoors, choose sunlight-resistant, water-resistant, or direct-burial options as required by the site.

Solid copper pushes easily through walls and holds shape at the stat base; stranded copper bends better at tight corners and service loops. A brown or white PVC jacket blends with trim; color-coded conductors (R, W/W1, Y, G, C, O/B, W2/Aux) speed identification. Shielded variants help reduce interference near motors or line-voltage runs.

• Match conductor count to equipment now and future add-ons; extra spares reduce truck rolls.
• Confirm thermostat and HVAC board specs: 18 AWG, 300 V rating, temperature rating.
• Use plenum-rated cable in return-air spaces; never substitute speaker or bell wire.
• Keep low-voltage runs 12 inches away from 120/240 V cables; cross at 90 degrees if needed.
• Leave slack at both ends, label wires, and secure with low‑tension staples.

Stock common lengths like 25, 50, 100, 250, and 500 ft spools for pull efficiency. Pair with a fish tape, wire strippers, and a toner to trace legacy circuits during retrofits.

Choose high-quality thermostat wire for dependable HVAC control, cleaner smart thermostat upgrades, and code-compliant installations on residential and light commercial projects. Find 18/5 thermostat cable, C-wire solutions, and plenum thermostat wire here. Ready to ship.