For an 80,000 BTU gas furnace with a 3-ton cooling system, what size copper conductor is normally used?

The copper conductor size for an 80,000 BTU gas furnace paired with a 3-ton cooling system typically falls within the 12 to 14 AWG range. This sizing is largely based on the amperage requirements of the furnace and cooling system combined.

In residential HVAC systems, it’s important to consider the current draw, which correlates to the equipment's BTU output and tonnage. For 80,000 BTU gas furnaces and 3-ton air conditioning systems, the electrical load typically requires conductors that are thick enough to safely carry the current without overheating.

Choosing 12 to 14 AWG wiring appropriately balances conducting the necessary current while not being excessively large, which could lead to unnecessary expense and difficulty in installation. Thicker wires are required for systems demanding higher currents, while lighter wires can suffice for lower draws, making 12 to 14 AWG a practical choice within these parameters.

It's also integral to comply with local electrical codes and the National Electrical Code (NEC), which provide guidelines regarding the safe and efficient sizing of conductors for different applications.