You've hit on a key point of debate and the correct answer depends on the specific application and how the generator is connected. Let's break it down

Understanding the Goal: Grounding for Safety

The primary purpose of grounding (in this context) is to provide a low-impedance path for fault current to return to the source (the generator), allowing overcurrent protection devices (breakers or fuses) to quickly trip and clear the fault. This minimizes the risk of electric shock.

Two Main Scenarios with Portable Generators

1.

Generator Supplying Power Through Extension Cords (No Connection to Building Wiring)



Requirement (per NEC 250.34)

Generally, a portable generator used only with cord-and-plug-connected equipment does not need to be connected to a grounding electrode (ground rods).

Reasoning

These generators are typically designed to be separately derived systems. Their frames and any exposed metal parts of the equipment plugged into them are bonded together. In this case, the generator is providing isolated power from the utility grid. The path for fault current is within the generator and the cord-connected equipment.

GFCI Protection

It's highly recommended, and often required, that these generators have GFCI protection built into their receptacles. The GFCI is what protects against ground faults in this scenario.2.

Generator Connected to Building Wiring (Using a Transfer Switch or Interlock)



Requirement (per NEC 250.30)



YES, the generator needs to be properly grounded. This is where it gets important. You must bond to the existing GEC to the house grounding electrode system. Reasoning

When the generator is connected to the building wiring, it becomes a separately derived system and it's now electrically connected to the building's grounding system. If a fault occurs on the generator side, the fault current needs a reliable path back to the generator to trip the breaker. That path is provided by the connection to the building's grounding system.

How to Bond

Typically, you would run a grounding electrode conductor (GEC) from the generator's frame (where a grounding lug is provided) to: The building's grounding electrode system (the same grounding electrode the service panel uses – ground rods, water pipe, etc.).

Transfer Switch/Interlock is Crucial

Using a properly installed transfer switch or interlock is essential to prevent backfeeding power onto the utility grid.

Why Not Both (Separate Ground Rods for the Generator and Bonding to the Building GEC)?

While it might seem like "more is better," having separate, unbonded grounding electrode systems can actually increase the risk of a ground potential difference between the generator and the building. In the event of a fault, this voltage difference could create a shock hazard. The NEC generally wants one unified grounding system.

In summary



Cord and Plug ONLY

Typically, NO ground rods needed. Rely on the generator's GFCI protection.

Connected to Building Wiring (transfer switch/interlock)

YES, you

MUST bond the generator's frame to the building's existing grounding electrode system (GEC). Do NOT use separate ground rods.

Important Considerations



Local Codes

Always check and adhere to local electrical codes and regulations. They may have specific requirements for generator grounding.

Qualified Electrician

If you are unsure about any of this, hire a qualified electrician. Improper grounding can be extremely dangerous.

Generator Instructions

Always follow the generator manufacturer's instructions.

Transfer Switch/Interlock

Make sure the transfer switch or interlock is properly installed and rated for the generator.

In conclusion, you are correct: the main goal is to trip the existing overcurrent devices for safety. Connecting the generator to the building GEC is the standard and safest way to accomplish this when the generator is connected to the building's wiring via a transfer switch or interlock. Flag for review