Let's break down your questions about electrical codes, specifically as they relate to older installations and potential changes over time. Keep in mind that interpretations and enforcement can vary by local jurisdiction. This information is for general understanding and not a substitute for professional advice from a licensed electrician.1. Remote Building Feeds with 3-Wire & Bonnet Neutral



General Principle

You're correct that using only three wires (two hots and a neutral) for a remote building feed, especially to a subpanel inside a building, is generally

not permitted under current code (NEC). This is primarily due to the separation of neutral and ground requirements. Reasoning



Safety

Having a separate equipment grounding conductor (EGC) is crucial for safety. If a fault occurs in the remote building, the EGC provides a low-impedance path back to the service, allowing a breaker to trip quickly and reducing the risk of electrical shock. A shared neutral/ground (as in a 3-wire with a bonnet neutral) can create a shock hazard if the neutral becomes compromised.

Voltage Drop

A separate EGC isn't intended to carry normal load current, reducing voltage drop compared to a shared neutral/ground.

NEC Requirements

The NEC requires a 4-wire system (two hots, neutral, and a separate EGC) for feeders supplying separate buildings or structures.

Was it Ever Allowed? While earlier versions of the NEC might have had some language allowing for a shared neutral/ground under very specific circumstances (e.g., certain outbuildings), it was never considered best practice, and certainly not for feeding a subpanel inside a separate building. Even in the 1970s, this would have been highly unusual for a commercial building to feed a subpanel within a separate building. The risks outweigh any perceived cost savings. Older installations might have been grandfathered in but would likely be flagged if modifications or expansions were done to the circuit.2. Service Conductors Through a Building (80 Feet, Unfused, Commercial)



"Nearest Point of Entry"

The concept of the "nearest point of entry" has become more clearly defined over time in the NEC, but the principle has always existed. The intent is to limit the distance unprotected service conductors run inside a building to minimize fire hazards.

NEC Requirements for Service Conductors Inside a Building



Overcurrent Protection

Service conductors must be protected by an overcurrent device (fuse or circuit breaker) as close as practicable to the point where they receive their supply.

Distance Limitations

Modern NEC specifies maximum lengths and installation methods for unfused service conductors inside a building. This length varies depending on the specific NEC edition and the type of building (residential vs. commercial).

1970s Standards

In the 1970s, the interpretation of "nearest point of entry" might have been more flexible or less explicitly defined in the code itself. However, the fundamental principle of providing overcurrent protection as close as possible to the source was still a core safety requirement. An 80-foot run of unfused service conductors inside a commercial building, even in the 1970s, is highly suspect and likely not compliant, especially if it created a significant fire risk. Inspectors would have been looking at factors like: The type of building construction. The type of wiring method used (e.g., in conduit vs. not). The potential for physical damage. The availability of a closer location for the overcurrent device.

"Vague Term Added Later"

It's not accurate to say that "nearest point of entry" was a vague term added later. The clarity and enforcement of that concept have certainly evolved and become stricter over time with code updates. It has always been necessary.

Important Considerations



Grandfathering

Just because something was installed "back then" doesn't automatically mean it's now compliant. While existing installations are often "grandfathered" (i.e., they don't have to be brought up to the current code unless modifications are made), any modifications or expansions will trigger the need to comply with the current code. If the existing installation presents a significant safety hazard, an inspector can require it to be corrected, regardless of its age.

Local Amendments

Remember that local jurisdictions can (and often do) amend the NEC to make it more stringent or to address specific local conditions.

Professional Evaluation

If you are dealing with an older electrical installation, especially in a commercial building, always have it inspected and evaluated by a qualified and licensed electrician. They can assess the safety of the existing wiring, identify any code violations, and recommend appropriate corrective actions.

In summary: Feeding a subpanel inside a building with a 3-wire system and a shared neutral/ground was generally never accepted. While the definition of "nearest point of entry" for service conductors has become more precise over time, the principle of providing overcurrent protection as close to the source as possible has always been a fundamental safety requirement. An 80-foot run of unfused service conductors inside a commercial building, even in the 1970s, would likely have been problematic.Do not* rely solely on this information for making decisions about electrical work. Always consult with a qualified electrician. Flag for review