Thermostat Wire

Solid-conductor thermostat wire in 18 AWG and 20 AWG. The 18 AWG range covers 2, 3, 4, 5, 6, 7, 8 and 10 conductors; 20 AWG covers 2, 4, 5, 6, 7 and 8. All of it is CL2 rated, with one CL2P plenum-rated 18/8 for plenum runs.

Conductor count is the decision. A straight cooling changeover needs fewer wires than a heat pump with auxiliary heat, a humidifier, a common wire and a condensate switch — and running a spare pair on the first pull beats pulling a second cable on the callback. Of the two gauges, 18 AWG is the heavier and the usual choice for longer runs.