Introduction to Open Return Wiring

The open return wiring system was an innovative method of wiring homes economically in the 1930s. This wiring system used a common neutral wire that returned all electrical currents to the service panel, allowing each circuit to share the neutral wire.

Prior to open return wiring, homes were wired using knob-and-tube wiring. This involved running individual hot and neutral wires through the walls and ceilings for each circuit. While effective, knob-and-tube wiring was labor intensive and used twice as much copper wire compared to the open return system.

The open return system was cheaper, faster to install, and used less materials. However, it came with some drawbacks that I'll discuss later on. First, let's look at how the open return wiring system worked.

How the Open Return Wiring System Functioned

The open return wiring system consisted of a shared neutral wire that provided a return path for all the electrical currents in the home. Here's a quick overview of how it worked:

This meant that only one neutral wire could provide the return path for multiple circuits. The neutral wire was often a bare wire that simply ran through holes drilled in the wall studs and floor joists.

The Cost and Labor Savings of Open Return Wiring

The open return system delivered huge savings in materials and manpower compared to knob-and-tube wiring:

These savings allowed 1920s wiring methods to be adapted for the surge in home construction that took place in the late 1930s. It simply wasn't feasible to wire all the new suburban homes using old-fashioned knob-and-tube.

The open return system brought electrification within the budget of more homeowners. This spurred the spread of electrical appliances beyond just lighting.

Safety and Reliability Concerns with Open Return Wiring

While effective and affordable, the open return system came with some potential hazards:

The open return system was also less compatible with modern appliances and electronics that produce electrical noise. This electrical interference can cause problems when many circuits share a neutral.

Overall, open return wiring provided adequate safety when properly installed. But it lacked the reliability of having dedicated neutral wires.

The Decline of Open Return Wiring

By the 1950s, the electrical code started prohibiting open return wiring in new construction:

Today, open return wiring is prohibited by the National Electrical Code. But it still exists in many older homes, especially in rural areas.

Identifying and Replacing Open Return Wiring

Here are some signs your home may have open return wiring:

If open wiring exists, it's best to have a licensed electrician inspect and replace it. They can:

While open return wiring served its purpose in the 1930s, upgrading provides much better safety, capacity, and reliability for modern households.


The open return wiring system enabled affordable electrification of homes in the 1930s. While not as safe as modern wiring, it allowed new suburbs to be wired quickly and inexpensively. The reduced use of copper wire was also important for wartime supply needs in the 1940s.

This little-known wiring method helped bring electricity to the masses. But its limitations and risks eventually led to stricter electrical codes mandating grounded, dedicated neutrals for each circuit. Although mostly forgotten, open return wiring remains an innovative electrical solution that powered the homes and appliances of its era.