How to Wire 110V for a Furnace | eHow How to Wire 110V for a Furnace. The blower and control circuit for a modern gas furnace uses its own 110 to 125 volt circuit breaker. A single sheathed cable runs from the circuit breaker to a single-pole light switch located next to the furnace. The switch connects to the furnace inside a wiring box. The furnace uses the power directly to run the.. Lennox Furnace Thermostat Wiring Diagram | Fuse Box And Mar 02, 2016lennox furnace thermostat wiring diagram - thanks for visiting my web site, this blog post will certainly review concerning lennox furnace thermostat wiring diagram. We have actually gathered many images, hopefully this picture is useful for you, as well as Thermostat Wiring Explained - electrical-online The most basic of systems (such as an older ‘heat only’ forced air / gas furnace with a standing pilot light) only need two wires for control. They connect to a two-wire thermostat (generally a mechanical thermostat with a mercury filled ball connected to a coiled bi-metal strip).