3 Wire Boiler Thermostat March 7, 2019 Fast. 2-wire Install (R and W contacts) If your current thermostat only has 2 wires present and if your furnace/boiler has standard R, W, and... support.ecobee.com Images Of Circuit SwitchingBlaupunkt Car Audio Wiring DiagramDifferent Electrical SwitchesTrailer Hitch Electrical WiringHow To Read Relay DiagramPioneer Avic F900bt Wiring DiagramCopper Romex WireThermostat Wires Explained