In 2025, a West African fintech company lost $4.2 million in transaction revenue when their single 800 kW generator failed during a 6-hour grid outage. The root cause? A faulty fuel lift pump — a $200 component that took their entire data center offline because there was no redundancy.

That event triggered a board-level mandate: every data center they operate must have N+1 generator redundancy. Their question to Tesla Power: “Can we just install a second identical generator and have them share the load automatically?”

The answer is yes — but paralleling two Volvo China diesel generator set units is not as simple as wiring them together and flipping a switch. The synchronization, load sharing, protection, and failover systems must be engineered correctly, or you risk the very scenario you are trying to prevent: both generators going offline simultaneously.

Here is the complete engineering guide to paralleling Volvo generators for data center backup power — the guide I wish every data center operator had before their first outage.

What Does “Parallel Operation” Actually Mean?

Parallel operation means two or more generators are electrically connected together and synchronized to supply power to a common bus. They share the load between them, and if one unit fails, the surviving unit automatically picks up the full load.

Think of it like a two-engine airplane. Either engine can fly the plane alone — but together, they share the work and provide redundancy if one fails.

The technical requirements for paralleling are exacting:

• Identical voltage: Both generators must produce the same voltage (230V/400V) within ±0.5%
• Identical frequency: Both must run at exactly the same speed — 1,500 RPM for 50 Hz or 1,800 RPM for 60 Hz. A difference of just 0.2 Hz causes circulating currents that overheat the alternators
• Identical phase sequence: L1-L2-L3 must match on both generators. If the phase sequence is reversed, connecting them will cause a catastrophic short circuit
• Identical phase angle: At the moment of connection, the voltage waveforms from both generators must be at the exact same point in their cycle — a difference of even 10° creates damaging transient currents

This precision cannot be achieved manually. You need a dedicated paralleling controller.

The Controller — The Brain of a Parallel System

The controller manages everything: synchronizing the generators before connecting them, adjusting fuel to share the load equally, detecting failures, and executing automatic load transfer when one unit trips. At Tesla Power, we specify two controllers for data center parallel systems:

ComAp InteliGen NT G2 (Our Primary Recommendation)

This is the industry-leading paralleling controller for medium to large generator installations. Its capabilities for data center backup power include:

• Automatic synchronization: Matches voltage, frequency, and phase angle within 0.5 seconds
• Active load sharing: Distributes real power (kW) proportionally to each generator’s capacity. If one generator is rated at 400 kW and the other at 600 kW, the controller assigns load in a 40:60 ratio
• Reactive power sharing: Balances kVAr between generators by adjusting alternator excitation
• Automatic failover: If one generator trips on fault, the surviving unit ramps up to full load within 5–10 seconds. No data center power interruption
• Load-dependent start/stop: System can be configured to run only one generator during low-load periods (e.g., at night) and automatically start the second when load exceeds a threshold
• Modbus communication: Both controllers communicate via a CAN bus, sharing speed, voltage, and load data 10 times per second
• Remote monitoring: WebSupervisor platform provides real-time dashboard accessible from anywhere

Deep Sea DSE8610 (Budget Alternative)

The DSE8610 supports 2-generator paralleling with automatic synchronization. It costs approximately 30% less than the ComAp system but has fewer advanced features (no web-based remote monitoring, limited communications options). Suitable for smaller data centers where cost is a primary constraint.

Step-by-Step: How to Set Up a Parallel Volvo Generator System

Step 1: Size the System

The fundamental question: what is your total load, and what level of redundancy do you need?

Critical data center sizing rule: Your combined generator capacity must exceed your critical IT load by at least 25% (N+1 margin). If your data center draws 600 kW, you need two generators totaling at least 750 kW. Common configuration: two identical 500 kW generators. Each unit can carry the full 600 kW load alone with headroom to spare.

See our power calculation guide for data center loads.

Step 2: Specify Matching Generators

While it is technically possible to parallel different-sized generators, Tesla Power strongly recommends identical units for data center applications:

• Same engine model (Volvo TAD1643GE)
• Same alternator model (Leroy-Somer LSA 49.1)
• Same controller firmware version
• Same fuel system configuration
• Same canopy type and cooling system

Matching units simplify configuration, ensure proportional load sharing, and allow swapping parts between generators for faster maintenance.

Step 3: Design the Electrical Architecture

The parallel system has a specific electrical topology:

1. Generator 1 → Circuit Breaker 1 → Common Bus
2. Generator 2 → Circuit Breaker 2 → Common Bus
3. Common Bus → Main Circuit Breaker → ATS → Data Center

Key components:

• Generator circuit breakers: Motorized, electrically operated. The controller opens and closes them during synchronization and failover. Rating: must exceed the generator’s full-load current by 25%
• Common bus: Copper busbar connecting both generator breakers to the main output. Must be rated for the combined current of both generators
• Main circuit breaker: Protects the data center from faults downstream. Usually a 3-phase molded-case circuit breaker (MCCB)
• ATS (Automatic Transfer Switch): Detects grid failure and initiates generator start sequence. Must be rated for the full data center load
• CAN bus communication cable: Connects the two controllers. Must be shielded twisted-pair cable, maximum 100 meters between controllers
• Battery backup for controllers: Each controller needs independent battery power (not shared) so one controller’s failure does not affect the other

Step 4: Configure the Controller Parameters

The controller must be programmed with specific parameters for data center operation:

ParameterData Center SettingWhy

Voltage setpoint400V ± 0.5%IT equipment requires tight voltage regulation
Frequency setpoint50.0 Hz ± 0.2%UPS systems sync to generator frequency
Sync windowVoltage: ±2%, Frequency: ±0.3Hz, Phase: ±5°Tight enough for safe connection, wide enough for reliable sync
Load sharing tolerance±5% of rated powerPrevents one generator from being overloaded
Failover time10 seconds maxUPS batteries bridge the gap
Cool-down time5 minutesProtects turbocharger after load removal
Start retries3 attemptsPrevents repeated cranking on a hard-to-start condition

Step 5: Commissioning — The Critical Test Sequence

Before putting the system into service, perform this test sequence in the presence of the data center facility manager:

1. Individual unit test: Start each generator independently, run at full load for 1 hour, verify all parameters normal
2. Synchronization test: Start Gen 1, sync Gen 2 to the bus. Verify voltage and frequency match within tolerance. Record sync time (should be under 30 seconds)
3. Load sharing test: Apply 25%, 50%, 75%, and 100% of total rated load. At each step, verify both generators share proportionally within ±5%
4. Failover test (the moment of truth): With both generators running at 50% total load, trip Generator 1’s circuit breaker. Verify Generator 2 picks up the full load without voltage dip exceeding 15%. Time the recovery — it must be under 10 seconds
5. Reverse failover: Restart Gen 1, resynchronize, return to shared load. Trip Gen 2. Verify Gen 1 handles full load
6. Grid-to-generator transfer: Simulate grid failure. Verify ATS transfers to generator bus within 10 seconds. Verify both generators start and synchronize within 30 seconds of ATS command
7. Generator-to-grid return: Simulate grid restoration. Verify ATS retransfers to grid and generators cool down normally

The UPS Interaction — Why Data Center Paralleling Is Different

Data centers have UPS (Uninterruptible Power Supply) systems that bridge the gap between grid failure and generator start. This creates a unique dynamic:

• The UPS carries the load during the 10–30 seconds it takes the generators to start and synchronize
• When the generators pick up the load, the UPS switches from battery to bypass mode — the generators now supply power directly
• The UPS battery recharges from the generators — this creates an additional load (typically 10–15% of UPS capacity) that the generators must handle

Many data center operators underestimate the UPS battery charging load when sizing generators. A 500 kVA UPS system can draw 50–75 kW during battery charging — this must be added to the IT load when calculating total generator capacity. Our sizing guide accounts for UPS charging loads.

Product Specifications — Volvo 500kW Parallel Data Center System

Each unit in the N+1 pair:

• Engine: Volvo Penta TAD1643GE, 6-cylinder, turbocharged, EU Stage IIIA
• Rated Power: 400 kW / 500 kVA (Prime), 440 kW / 550 kVA (Standby)
• Alternator: Leroy-Somer LSA 49.1, brushless, IP23, ±0.5% voltage regulation, damper winding for UPS harmonic loads
• Controller: ComAp InteliGen NT G2 with CAN bus communication for parallel operation
• Circuit Breaker: Motorized MCCB, 800A, electrically operated
• Parallel Cable: Shielded CAN bus, 20m (pre-configured at factory)
• Fuel Consumption: 88 L/h at 75% load per unit
• Fuel Tank: 1,500L base-mounted per unit (24 hours at full load)
• Canopy: Super-silent, 62 dB(A) at 7m, 2.5mm steel, 75mm rock wool
• Dimensions: 3800 × 1600 × 2200 mm per unit
• Weight: 4,200 kg per unit
• Raw Materials: Q235B structural steel, polyester powder coat 200µm, marine-grade stainless hardware, copper busbars, heavy-duty rubber isolators
• Service Mode: Tesla Power provides on-site commissioning supervision, 72-hour load bank test, data center facility staff training, and 24/7 remote monitoring via ComAp WebSupervisor

Frequently Asked Questions

Q1: Can I add a third generator to my existing parallel system?

Yes. The ComAp InteliGen controller supports up to 32 generators in parallel. Adding a third unit simply requires installing the generator, connecting the CAN bus communication cable, and configuring the controller with the new unit’s parameters. Tesla Power can provide the additional unit and configuration for existing parallel systems.

Q2: What happens if one generator starts but fails to synchronize?

The controller will attempt synchronization up to 3 times. If synchronization fails (due to voltage mismatch, frequency instability, or phase sequence error), the controller will shut down the non-synchronizing unit, log the fault, and continue running on the synchronized unit. An alarm is sent to the remote monitoring platform. The data center experiences no power interruption because the synchronized generator is already carrying the load.

Q3: How does the system handle unbalanced loads across phases?

In a parallel system, unbalanced loads create circulating currents between the generators. The controllers detect this and adjust excitation to minimize circulating current. For data center applications, ensure your UPS system provides balanced output — most modern UPS systems include built-in load balancing. If you have significant phase imbalance, the controllers will compensate but at a slight efficiency cost.

Q4: Do I need a synchronizing panel separate from the generator controllers?

No. Modern controllers like the ComAp InteliGen NT G2 integrate synchronizing, load sharing, and protection functions into a single unit on each generator. No external synchronizing panel is required. This simplifies installation, reduces cost, and eliminates a potential single point of failure.

Q5: What is the minimum cable size between the generators and the common bus?

This depends on the generator’s full-load current and the cable routing distance. For a 500 kW Volvo generator at 400V three-phase, full-load current is approximately 722A. Minimum cable size is typically 2 × 240mm² copper per phase (parallel cables) for runs under 20 meters. Longer runs require larger cables to prevent voltage drop. Tesla Power provides detailed cable sizing calculations with every parallel system order.

Data center downtime costs are measured in thousands of dollars per minute. A properly designed parallel generator system with N+1 redundancy eliminates single-point-of-failure risk and protects your critical infrastructure. Tesla Power has designed and commissioned parallel generator systems for data centers across Africa and Asia — contact us for a complete parallel system design proposal.