Yes, connecting two floating neutral generators to the same neutral bar, even with the breakers for the generator-fed circuits off in the main panel, does create a potential for a parallel neutral path and a potentially dangerous situation. Here's why: Parallel Neutral Paths

The neutral bar in your sub-panel is bonded to the ground bar, which is ultimately bonded to the main service entrance neutral. By connecting the neutrals of both generators to this shared neutral bar, you create multiple paths for neutral current to flow. Specifically:

Generator 1 -> Sub-panel Neutral Bar -> Main Panel Neutral/Ground Bond -> Generator 2's Load -> Generator 2's Neutral. Generator 2 -> Sub-panel Neutral Bar -> Main Panel Neutral/Ground Bond -> Generator 1's Load -> Generator 1's Neutral. Consequences of Parallel Neutral Paths



Circulating Currents

Even with breakers off in the main panel, small differences in voltage or load between the two generators can cause current to circulate through the neutral-ground bond and the generator windings. This circulating current can be unpredictable and can overload neutral conductors.

Overheating

The neutral conductors are sized to carry the unbalanced current of a single circuit. With parallel paths, they could be carrying current from multiple circuits, potentially exceeding their ampacity and causing overheating, insulation damage, and even fire.

Voltage Imbalances

The uneven distribution of neutral current can lead to voltage imbalances in the circuits powered by the generators, potentially damaging sensitive electronics.

Safety Hazard

If the neutral connection to the utility fails and the generator neutral connection also degrades or fails, the generator's ground could become energized, creating a shock hazard.

Ground Fault Protection Problems

Ground Fault Circuit Interrupters (GFCIs) rely on sensing an imbalance between the hot and neutral wires. Parallel neutral paths can interfere with the proper functioning of GFCIs, rendering them ineffective.

Why Breakers OFF Don't Completely Solve the Problem

While turning off the breakers in the main panel for the generator-powered circuits reduces the active current flow, it doesn't eliminate the potential for current to flow through the shared neutral connection. Even with the breakers off, there's still a complete neutral path between the two generators through the sub-panel neutral bar and the main panel neutral-ground bond.

Floating Neutral Generator Implications

Floating neutral generators are designed to not have a neutral-ground bond within the generator itself. This is to avoid ground loops and parallel neutral paths when connected to a system with a pre-existing neutral-ground bond (like your main panel). Connecting multiple floating neutral generators in this way defeats the purpose of their floating neutral design.

Solutions & Recommendations

1.

Never connect the neutral from multiple floating neutral generators to the same neutral bar. This is the core issue.2. Single Generator at a Time

The safest approach with your current setup is to only use one generator at a time. Completely disconnect the other generator before starting and connecting the first. This eliminates the parallel neutral path.3.

Neutral Switching Transfer Switches

The ideal solution is to use

transfer switches that switch the neutral wire. This disconnects the neutral from the utility service when the generator is connected, and connects the generator's neutral instead. This prevents the parallel neutral path. These are generally more expensive.4. Bonded Neutral Generators (Discouraged for your setup)

You could replace one or both generators with bonded neutral generators, but this is generally not recommended and requires careful consideration. If you did this, you'd have to ensure that the neutral of the floating neutral generator never* connects to the same neutral bar when the bonded neutral generator is in use. It's very easy to make a mistake, and the consequences are severe. Also, with bonded generators you would need to disconnect the neutral-ground bond on the generator that is not in use otherwise you're just making more and more ground loops.5.

Isolate the neutrals of the two manual transfer switches. If your generators each have a floating neutral and there are no other connections from one switch to the other, then there will not be a parallel neutral path. This would look like each generator has its own isolated system that consists of the manual transfer switch, generator, and circuits. These are simple and affordable setups for temporary power, however it is only safe and up to code if each system (generator, manual transfer switch, and circuits) is isolated from one another. The downside is the circuits running off one generator cant be connected to the other.

IMPORTANT WARNING: Improperly wiring generators can lead to fire, electrocution, and damage to equipment. If you're not absolutely sure about what you're doing, consult a qualified electrician. This information is for general understanding and should not be substituted for professional advice. Modifying electrical systems can be dangerous, and mistakes can be fatal. Flag for review