Why Euro 6 gensets often break down at low load (construction site explanation)

Why Euro 6 gensets often face problems at low load

Many construction sites have a diesel generator running all day. But often the construction site uses only one small fraction of available assets. A 100 kVA genset delivering only 20-30 kVA runs on approximately 20-30% load. This seems efficient. In reality, it actually causes technical problems.
More and more contractors and rental companies are finding that modern Euro 6 gensets are more likely to malfunction when running at low load for long periods.

To understand why, let's look at how a diesel engine works.

Diesel generators are designed for high loads

A diesel engine works most efficiently when running under a relatively high load.
Under the circumstances:

• the engine reaches the correct operating temperature
• combustion proceeds fully
• exhaust gases are treated effectively

When the load is too low, the opposite happens. The engine runs, but produces insufficient heat and pressure for optimal combustion.

The problem of incomplete combustion

At low load incomplete combustion of diesel fuel. This leads to:

• soot formation
• fouling of injectors
• deposits in the cylinders
• contamination of the exhaust system

This phenomenon is known in the industry as “wet stacking”. The fuel does not burn completely and leaves residue in the system. Wet stacking occurs when unburned fuel and soot accumulate in the exhaust system due to the engine not reaching a sufficient temperature.

Why aggregates on construction sites are often too big

On many construction sites, a genset is chosen based on peak power. As a result, there is often an 80 or 100 kVA genset while the average consumption is only 20-30 kVA. As a result, the genset runs at low load most of the day. Many projects therefore look at alternative energy solutions such as mobile energy supply with a Battery box.

Euro 6 compounds the problem

Modern gensets include extensive emission systems, such as:

• Diesel Particulate Filters (DPF)
• Selective Catalytic Reduction (SCR)
• AdBlue systems
• Exhaust Gas Recirculation (EGR)

These systems only function properly when the engine gets sufficiently hot. At low load, the temperature often remains too low to effectively regenerate the particulate filter. The result:

• blockage of the DPF filter
• error messages
• emergency stops
• additional maintenance

Why this is so common on construction sites

On many construction sites, a generator generously dimensioned. This is done to handle peak loads. But in practice, machines do not run continuously at peak power. As a result, the aggregate:

• is too large for daily consumption
• runs for long periods at low load
• becomes inefficient and prone to failure

Alternative energy solutions

More and more projects are therefore looking at alternatives to traditional generators. Energy storage can, for example:

• absorb peak loads
• temporarily store energy
• supporting the electricity grid

Storing energy and delivering it only when needed creates a more stable energy system on site. Many projects therefore look at alternative energy solutions such as mobile energy storage with a Battery Trailer.

Conclusion

Diesel generators function best at high load. When they run at low load for long periods, technical problems such as soot formation, fouling and failures in emission systems occur.

At a time when construction sites are increasingly electrifying, it is therefore becoming more important to supply energy organising smarter rather than simply installing larger generators. This can be done with our mobile solutions such as the Battery box and the Battery Trailer