You're describing a potentially hazardous and certainly outdated electrical service arrangement. Let's break down the code requirements and timeline regarding grouped disconnects and the issues you're encountering.

NEC Requirement for Grouped Disconnects (Services)

The National Electrical Code (NEC) generally requires that service disconnecting means be grouped and readily accessible. This is to ensure that in an emergency, all power to the building can be quickly and safely shut off from one location.

NEC 230.72 (General)

This is the primary section of the NEC that mandates grouping of service disconnects.

NEC 230.71 (Maximum Number of Disconnects)

This section deals with the allowable number of disconnects per service. If your duplex has separate services, it would fall under this rule. The number of allowable disconnects has changed over time, but the general trend has been towards limiting the number.

Timeline and Evolution of the Code



Pre-1960s

Electrical codes were far less standardized and enforced than they are today. Many older installations, especially in rural areas, were done with minimal oversight. Your described service setup is more likely to be from this era, especially the use of split bus panels.

1960s-1980s

Code revisions began to emphasize safety and uniformity. Requirements for grounding, overcurrent protection, and service equipment became more stringent. The concept of a single main disconnect or a limited number of grouped disconnects started to gain traction.

1990s and Onward

The push for grouped disconnects and easily accessible service equipment became more pronounced. Modern NEC editions place a heavy emphasis on safety features and reducing the potential for electrical hazards.

Split-Bus Panels and the 6-Disconnect Rule



Split-Bus Panels

These panels, commonly found in older homes, have a main breaker section and a lighting and appliance branch-circuit section. The main section is fed directly from the meter.

The "Rule of Six"

Older versions of the NEC (roughly up to the 1980s) allowed up to six main disconnects on a service. This is why you see those split-bus panels with multiple breakers feeding the lower sections.

Why They're Outdated

The "rule of six" disconnects are not considered safe by today's standards. In an emergency, it's too difficult and time-consuming to locate and shut off all the breakers. Modern split bus panels no longer have the ability to have multiple disconnects.

The Specific Problem with Your Duplex Service

The configuration you describe violates modern NEC standards for several reasons:1.

Lack of Grouped Disconnects

The fact that you have to access two separate locations (one on each side of the duplex) to de-energize the entire building is a major safety issue.2.

Multiple Disconnects per Service (Potentially)

Even if each side of the duplex has its own service, having six disconnects on each side exceeds modern code requirements.3.

Accessibility

If the disconnects are not readily accessible to the occupants, this is also a violation.4.

Obsolete Equipment

Split-bus panels are generally considered outdated and less safe than modern panels with a single main breaker.

When Did This Code Adopt? A good rule of thumb is any build or major electrical renovation in the 1990's or later would not pass code as you describe.* The emphasis on a single, readily accessible disconnect for a service has been building gradually since the 1960s, but the modern interpretation with strong enforcement is largely a product of the last few decades.

Recommendations for Replacement


Consult with a Licensed Electrical Contractor

Do not attempt to replace or modify this service yourself. An experienced electrician can assess the existing setup, determine the best course of action, and ensure that the new installation complies with all applicable codes.2.

Upgrade to Modern Service Equipment

This likely involves replacing the split-bus panels with modern panels that have a single main breaker.3.

Group the Disconnects

The new service disconnects must be grouped in a readily accessible location, ideally on the exterior of the building.4.

Consider Meter Placement

Depending on local utility requirements, you may need to relocate or consolidate the meters.5.

Permits and Inspections

Make sure your electrician obtains the necessary permits and schedules inspections to ensure the work meets code requirements.

In summary: Your described duplex service is likely a relic of an earlier era when electrical codes were less strict. Replacing it with modern equipment that meets current NEC requirements is essential for safety and compliance. The trend towards grouped, easily accessible disconnects has been evolving for decades, but the modern interpretations with strict enforcement are largely a product of the last few decades, making it unlikely that the current setup would meet code if it were installed or significantly altered since the 1990s. Always prioritize safety and consult with qualified professionals. Flag for review