Okay, this is a good question, and it's great you're asking for clarification. Let's break it down step-by-step to help you understand the situation and the best options.

Understanding the Loads and NEC Articles Emergency Loads (NEC 700)

These are absolutely critical for life safety. Think lighting for exit routes, fire pumps, elevators, and other systems necessary for safe evacuation and building operation during a power outage.

Reliability is paramount. Legally Required Standby Loads (NEC 701)

These are loads required by law to have standby power. Examples include ventilation systems in hazardous locations, sewage disposal, communication systems, and some types of fire alarm systems. These are important but not as critical as emergency loads.

Optional Standby Loads (NEC 702)

These are loads the owner chooses to have backed up, typically for business continuity or convenience. Examples include HVAC, computer systems, and production equipment. The owner is choosing to have these run during an outage, so they're "optional."

Key Points Regarding Load Separation NEC 700 (Emergency)

Must be completely independent. This means: Separate wiring from the generator to the emergency loads. Separate raceways (conduit) from the generator to the emergency loads. Separate overcurrent protection (circuit breakers) for the emergency loads. Separate transfer switch (if applicable) for the emergency loads. As you mentioned, the emergency loads should not share the same vertical section or panelboard as other loads.

NEC 701 (Legally Required) and NEC 702 (Optional)

These can be combined on the same system. The Code gives you more flexibility here. They can share wiring, raceways, overcurrent protection, and a transfer switch, if desired.

Generator Breakers vs. Panelboards/Switchboards

The question is: Can you achieve the required separation and load management using only breakers on the generator itself, or do you need separate panelboards/switchboards downstream? Generator Breakers

Many generators come with a few (typically 1-3) circuit breakers built into the generator enclosure. These are primarily for protecting the generator itself from overloads and short circuits. While technically possible, using only the generator breakers to feed all three load types is generally not the best practice, especially considering NEC 700 requirements.

The main reason this is not a good idea is you cannot easily and reliably achieve the complete physical separation required for emergency loads (NEC 700). Even if the generator has multiple breakers, all the wiring is likely to be bundled within the generator enclosure, violating the separation requirement. Panelboards/Switchboards

These are distribution points where power from the generator is further divided into individual circuits to feed the various loads. Panelboards are typically smaller and have lower ampacities than switchboards.

Using panelboards/switchboards is the recommended approach. Here's why: Compliance with NEC 700 Separation

You can easily create a dedicated panelboard specifically for the emergency loads. This panelboard is fed directly from the generator (via its own dedicated circuit breaker), and all the wiring from this panelboard to the emergency loads is completely separate from other wiring.

Load Management and Protection

Panelboards provide individual circuit breakers for each load, allowing for better protection and control.

Flexibility and Future Expansion

Panelboards make it easier to add or modify circuits as needed in the future.

Ease of Maintenance

Easier to isolate and work on specific circuits.

Recommended Approach1. Dedicated Emergency Panelboard (NEC 700)

Run a dedicated feeder (wires in conduit) from a dedicated circuit breaker on the generator to a panelboard labeled "Emergency." This panelboard feeds only the emergency loads. The entire installation from the generator breaker, the feeder to the panelboard, and from the panelboard to the emergency loads, must be completely separate and independent from all other systems.2.

Combined Legally Required/Optional Panelboard (NEC 701/702)

Run a separate feeder from a different circuit breaker on the generator to another panelboard (or switchboard). This panelboard can feed both the legally required standby loads and the optional standby loads.3.

Transfer Switches (if applicable)

You'll likely need automatic transfer switches (ATS) to switch the loads between the normal power source (utility) and the generator. The emergency loads must have a dedicated ATS that is separate from the ATS for the other loads. The legally required and optional loads can share an ATS, or you can provide a separate ATS for each, depending on the specific design requirements.

Visualizing the Solution

Imagine the following setup:`Utility Power Source``|``Automatic Transfer Switch (Emergency)` --> `Emergency Panelboard (NEC 700)` --> `Emergency Loads``|``Generator` --> `Circuit Breaker` --> Dedicated Conduit -->`Emergency Panelboard (NEC 700)``|``Utility Power Source``|``Automatic Transfer Switch (Legally Req./Optional)` --> `Combined Panelboard (NEC 701/702)` --> `Legally Req. Loads & Optional Loads``|``Generator` --> `Circuit Breaker` --> Dedicated Conduit --> `Combined Panelboard (NEC 701/702)`In summary

You need at least two panelboards/switchboards to properly separate the emergency loads (NEC 700) from the other loads, as required by code. Using only the generator breakers is not a recommended or compliant solution.

Important Considerations



Consult the Local Authority Having Jurisdiction (AHJ)

Always consult with the local electrical inspector or AHJ to ensure your design meets their specific requirements and interpretations of the NEC.

Load Calculations

Accurately calculate the total load for each category (emergency, legally required, optional) to ensure the generator is sized appropriately.

Generator Size

Select a generator that has the capacity to handle all the connected loads simultaneously.

Coordination

Ensure the overcurrent protection devices (circuit breakers) are properly coordinated to minimize nuisance tripping and ensure selective fault clearing.

Single-Line Diagram

Create a detailed single-line diagram to document the entire system, including the generator, transfer switches, panelboards, and loads. This will be invaluable for future maintenance and troubleshooting.

Disclaimer: This information is for educational purposes only and should not be considered a substitute for professional engineering advice. A qualified electrical engineer should be involved in the design and installation of any standby power system. Flag for review