Okay, let's break down your generator setup and address the concerns. The electrician who raised the "explosion" concern is partially correct in identifying a potential problem, but their phrasing is a bit extreme and the actual risk is likely backfeeding and potential equipment damage rather than an explosion.

Understanding the Issue

The core problem is parallel operation of generators. You cannot simply connect two generators supplying the same system (even if they're powering different panels downstream of the same service) without proper synchronization and control. Here's why: Voltage Differences

Even though your two generators are nominally 120/208V, the actual instantaneous voltage and phase angle of each generator will be slightly different. If you directly connect them, one generator will essentially try to "force" the other to match its voltage and phase. This results in a large circulating current between the generators, which can damage windings, breakers, and potentially even the generators themselves.

Backfeeding

If your single-phase generator is running and powering one panel, and the three-phase generator is then switched on to power the three-phase panel, there's a high probability that power from one generator can "backfeed" through the load, into the other panel.

How to Safely Integrate the 80kW 3-Phase Generator

Here's the proper approach to integrate your 80kW generator while keeping your existing single-phase generator. The key is to ensure complete isolation between the generator circuits during normal grid power and during generator operation:1. Three-Phase Automatic Transfer Switch (ATS)

This is essential. You need a properly sized 3-phase ATS installed upstream of your 3-phase breaker panel. This ATS will have three positions:

Utility Power (Normal)

The panel is fed from the utility grid.

Off (Open Transition)

A very short break before switching from utility to generator or generator to utility.

Generator Power

The panel is fed from the 80kW generator.It should have a rating that matches your existing 3 phase panel bus rating.2.

Load Calculation

Before you do anything else, perform a load calculation of the equipment to be backed up by each generator. You need to know the actual load (in amps) on each panel. This is critical for sizing the generators and the transfer switches correctly. Don't rely on nameplate ratings alone. Use a recording ammeter (clamp meter) to measure actual current draw over a representative period.3.

Neutral Bonding (Important!)



Single-Phase Generator

Your existing single-phase generator, if portable, probably has a floating neutral. The transfer switch connecting it should SWITCH the neutral and ground, to avoid double bonding of neutral.

Three-Phase Generator

The 3-phase generator MUST have a bonded neutral within the generator enclosure. This bonding is typically located near the generator's output connections and is critical for providing a proper ground reference for the generator's output voltage and for fault protection.4.

Generator Selection

When selecting the generator, get one that has a digital voltage regulator. This will help to maintain constant and accurate output voltage.5.

Professional Installation

Do not attempt this work yourself unless you are a licensed and experienced electrician familiar with generator installations and electrical codes. A mistake could be dangerous and costly.

Operating Scenarios Normal Power (Utility Grid)

Both transfer switches are in the "Utility Power" position. All panels are powered by the grid.

Short Power Outage (Single-Phase Generator Only)

The single-phase generator's ATS detects the power outage and starts the generator. After a warm-up period, the ATS switches to the "Generator Power" position, powering the single-phase panel. The three-phase ATS remains in the "Utility Power" position (because the 3 phase generator is not called to run).

Extended Power Outage (Both Generators)

The single-phase generator's ATS detects the power outage and starts the generator. After a warm-up period, the ATS switches to the "Generator Power" position, powering the single-phase panel. You manually start the three-phase generator (since you said you only want it for extended outages). Or, if you choose to have an auto start three phase generator with auto transfer switch, then that switch automatically detects power outage and starts the generator and switches from utility to generator. After a warm-up period, manually switch the three-phase ATS to the "Generator Power" position. This will power the three-phase panel from the 80kW generator.

Important Considerations and Recommendations Permitting and Inspections

Generator installations require permits and inspections by your local electrical authority (AHJ). Make sure you obtain the necessary permits before starting any work.

Noise and Emissions

Consider the noise and emissions from the diesel generator, especially if you're in a residential or commercial area. Local regulations may restrict operating hours or require sound attenuation measures.

Maintenance

Generators require regular maintenance, including oil changes, filter replacements, and battery checks. Schedule routine maintenance to ensure reliable operation.

Coordination

The automatic transfer switches must be coordinated. Ideally, you want the 3 phase switch to wait 10-15 seconds longer than the single phase switch so that the smaller generator is up and running first.

In summary: You can have both generators, but you must* use transfer switches to ensure complete isolation and prevent dangerous parallel operation. Engage a qualified electrician to perform a load calculation, size the ATS, install the equipment, and ensure compliance with all applicable codes and regulations. This investment in professional installation will guarantee safe and reliable backup power for your business. Flag for review