Understanding Load Banks: Types, Benefits, and Best Practices for Diesel Generator Testing

Diesel generators are built to perform reliably — but only when operated and tested under proper load conditions. Running a generator below its designed load capacity can lead to carbon buildup, poor fuel combustion, and performance failures. That's why load bank testing is crucial to diesel generator maintenance, especially in critical applications.

Why Diesel Generators Need Load Bank Testing

Most diesel engines perform best at 70% to 80% of their rated output. However, many backup generators run well below this threshold during routine testing or standby mode. Operating under low-load conditions can cause wet stacking, where unburned fuel and carbon accumulate in the exhaust system.

Wet stacking leads to:

• Carbonized fuel injector tips
• Inefficient fuel spray patterns
• Reduced engine performance and lifespan

A load bank allows the generator to reach full operating temperature, helping prevent wet stacking and verifying the unit's ability to deliver power when needed.

Why Emergency Power Compliance Matters

Generator systems must meet strict standards for mission-critical facilities like hospitals and data centres, including NFPA 110, which outlines testing requirements for standby power systems. Consulting engineers must ensure that generator systems are tested and maintained in compliance with these standards to meet National Electrical Code (NEC) requirements.

Events like the 2003 blackout and Y2K preparedness efforts reinforced the importance of reliable emergency power — and the role of load bank testing in achieving that reliability.

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Types of Load Banks for Generator Testing

Selecting the correct type of load bank depends on your application, environment, and testing frequency. Below are the three most common types of resistive load banks and their best uses:

1. Radiator-Mounted Load Banks

Radiator-mounted load banks are cost-effective options that mount directly onto the generator set's radiator. They use the radiator's airflow for cooling and typically operate at 50% to 70% of the generator's rated capacity.

Key features:

• Compact design (~13 inches deep)
• It uses radiator exhaust airflow for cooling
• Installed during initial generator setup
• Requires heat-resistant materials (not galvanized steel)
• Ideal for non-100% load applications

Best practices:

• Avoid exceeding 70% rated capacity to prevent overheating
• Ensure construction with durable aluminum or stainless steel
• Include remote control panels and automatic load dump features
• Install with weatherproof enclosures for outdoor durability

2. Portable Load Banks

Portable load banks are versatile and ideal for indoor or mobile testing. They include metering systems and basic controls and can be moved to different locations using built-in casters.

Benefits:

• Flexible voltage options
• Simple setup and transport
• Useful for field testing and smaller generators
• Effective for spot-checking system performance

While unsuitable for large-scale permanent systems, they're ideal for routine monthly testing or rotating between multiple units.

3. Permanent Load Banks

Permanent load banks are designed for continuous use in facilities requiring regular testing. These freestanding units are typically installed on rooftops or concrete pads and are rated for 100% load capacity.

Advantages:

• Long-term durability in any weather
• No static pressure applied to the generator
• Compatible with remote control panels (50–250 ft away)
• Ideal for systems requiring full-capacity testing

Optional features include:

• Internal strip heaters for cold-weather operation
• CE, UL, CSA, or Canadian UL third-party certification
• Weatherproof construction for harsh environments

Specifying the Right Load Bank

When specifying a load bank, engineers should first identify:

• Generator voltage and kilowatt rating
• Required load level for testing (full or partial)
• Application environment (indoor, rooftop, plant room)
• Testing frequency (monthly, quarterly, etc.)

Permanent load banks are ideal when long-term reliability and full-load testing are required. Radiator-mounted or portable options are better suited for budget-sensitive or space-limited projects.

Where Foxfab Fits In

While Foxfab does not manufacture or rent load banks, we provide the infrastructure required for testing safe, reliable, and code-compliant load banks.

Our Load Bank Connection Cabinets are:

• ETL Listed to UL1008 standards
• Available in wall- or pad-mounted configurations
• Built from 5052 aluminum, 304, or 316 stainless steel
• Rated for up to 4000A
• Designed with Camlock receptacles, keyed interlocks, and phase rotation protection

Installing a dedicated connection point enables faster testing, reduces setup time, and improves overall safety during generator maintenance.

Conclusion

Load bank testing is essential to maintaining the performance and reliability of your diesel generator system. Whether using a radiator-mounted, portable, or permanent load bank, the key is to test regularly and under the correct load conditions.

Engineers should:

• Follow manufacturer specifications
• Select appropriate load bank types and placement
• Ensure equipment is built for the environment
• Use dedicated connection points for testing infrastructure

Foxfab is here to support your power readiness — ensuring that your generator system performs as expected when the power goes out.

📩 Contact sales@foxfab.com or visit www.foxfab.com to learn more about Load Bank Connection Cabinets built for high-performance testing environments.

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