Okay, let's break down the requirements for a main service disconnect in your scenario, considering both the NEC 2017 and the context of Chicago's electrical practices.

NEC 2017 Analysis (with Chicago Considerations)

Based purely on NEC 2017, the "six disconnect rule" (NEC 230.71) is the primary relevant section, along with other supporting sections within Article 230 (Services). The Six Disconnect Rule (NEC 230.71)

This rule generally allows for up to six service disconnects for each service to a building. The intent of this rule is that someone responding to an emergency can readily disconnect all power to the building with a limited number of operations.

What Constitutes a Service

This is a crucial point. Each set of service-entrance conductors from the serving utility's drop or lateral is considered a service.



Applying it to Your Scenario

Your description indicates one service entrance, then splitting out to eight individual meters and breakers. If this is true, the six disconnect rule would apply.

NEC 230.71(A)

"The service disconnecting means for each set of service-entrance conductors shall consist of not more than six switches or six circuit breakers mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard."

Chicago Considerations

Chicago is known to have strict enforcement of the NEC and potentially stricter interpretations or local amendments.

The Argument for Requiring a Main DisconnectThe core reason for requiring a main disconnect is safety. Consider the following:

Emergency Situations

Firefighters or other emergency personnel need to be able to quickly de-energize the entire building. Having to locate and shut off eight individual breakers is time-consuming and dangerous.

Maintenance/Repairs

To perform maintenance on the service equipment upstream of the individual meter/breaker sets, a single point of disconnect is much safer and more efficient.

Clarity

It unambiguously establishes the building's service entrance location.

The Argument Against Requiring a Main Disconnect

Historical Practice

As you mentioned, you've seen installations without a main disconnect. This could be due to: Installations predating stricter code enforcement. Installations done with variances or special approvals (unlikely without good justification). Misinterpretations or oversights during past inspections. Local interpretation of the code by the AHJ.

Individual Tenant Control

Having individual disconnects allows each tenant to control their own power, which is generally desirable.

Best Practice and Recommendation1.

Contact the Chicago Electrical Inspection Department (AHJ)

This is the most critical step. Explain your exact scenario and ask them specifically about the requirement for a main service disconnect. Get their answer in writing (email is okay). Their interpretation of the code is what matters.2.

Provide Detailed Plans

If you haven't already, create detailed electrical plans that clearly show the service entrance, meter bank, individual breakers, and riser diagrams. Submit these plans to the AHJ for review.3.

Design for Compliance (Even if Not Strictly Required)

Consider the benefits of including a main disconnect, even if the AHJ doesn't strictly require it. It's a safer and more maintainable design. If you have space and budget, it's worth considering.

If the AHJ requires a main disconnect



Sizing

The main disconnect must be sized to handle the calculated load of all eight units. This is not simply the sum of the eight 100A breakers. Load calculations are covered in NEC Article 220. A licensed electrical engineer or very experienced electrician should perform this calculation.

Location

The main disconnect should be readily accessible and clearly labeled. Typically, it's located near the meter bank.

Important Considerations



Load Calculation

The size of the service entrance conductors and the main disconnect (if required) must be based on a proper load calculation (NEC Article 220). You can't just add up the individual breaker sizes.

Accessibility

All disconnects (main and individual) must be readily accessible.

Working Space

Sufficient working space (as per NEC 110.26) must be provided around the service equipment.

Overcurrent Protection

All conductors must be properly protected by overcurrent devices (breakers or fuses).

In summary

While it might seem that installations without a main disconnect are common,

contacting the Chicago Electrical Inspection Department is crucial to determine the specific requirements for your project. Err on the side of safety and compliance, and document all communication with the AHJ. If the AHJ says a main is required, there is no way around it. Flag for review