220 Volt Electric Furnace Wiring - Ask the Electrician 220 Volt Electric Furnace Wiring. How Do I Wire an Electric Furnace? Wiring Connections for 220 Volt Electric Heater and How to Connect the Electrical Circuit Wiring for a Furnace. What needs to be changed to make this work? There is 3 heavy gauge wires ran in but it has two breakers that takes 4 wires to connect. Reply. Dave Rongey says Wire Gauge For Furnace - Electrical - DIY Chatroom Home Aug 01, 2011Is this a heating system furnace or a pottery kiln? Double check the name plate. 15 KW does not sound right for a furnace. A 14 gauge wire cable (14-2 Romex) is typical for a gas or oil furnace and 55 feet is not too far for that wire size.