Gas Fitter Test 2026 – 400 Free Practice Questions to Pass the Exam

The primary voltage of a furnace commonly operates at 120 volts, particularly in residential settings where single-phase electrical systems are used. The specification "120/1/60" indicates that the furnace is utilizing a single-phase system with a primary voltage of 120 volts at a frequency of 60 hertz. This is standard in many North American homes as it provides adequate power for ignition systems and controls without requiring higher voltage levels.

While other voltage specifications such as "240/1/60" may also be common in heating systems, particularly for larger furnaces or certain configurations, the answer indicates that for this scenario, the primary voltage in question relates to the more typical lower voltage configuration found in many residential installations.

This answer implies that the furnace designed for 120 volts ensures that it is compatible with standard household electrical systems, making it more accessible to install and maintain. Higher voltage options generally indicate different requirements for circuit sizing and safety measures. The configuration of "120/2/60" would suggest a two-wire system instead of the standard one, which is uncommon for most residential furnace installations. Therefore, the specification provided identifies the correct, most commonly utilized primary voltage for typical furnace applications.