RECD for DG SetA diesel generator that runs only occasionally may seem like an unusual candidate for an emission-control retrofit. If a DG set operates only during power failures, emergency situations, seasonal events, or periodic testing, owners often wonder whether installing an is actually worthwhile.

The answer depends on more than annual running hours. The generator’s load, duration of each run, maintenance routine, exhaust temperature, and the length of idle periods all influence how effectively an emission-control system performs.

Occasional Use Does Not Mean No Maintenance

A rarely used DG set can actually face some specific operating challenges. Long idle periods allow moisture and condensation to accumulate in the exhaust system, while very short no-load tests may not allow the exhaust system to reach an effective operating temperature.

cpcb.nic.inThis is important because an RECD is part of the complete exhaust system and its performance depends on the conditions under which the generator operates. CPCB's technical material defines an RECD as a retrofit system designed to achieve particulate-emission reduction and notes that its regeneration strategy, sensors, controller and software can form part of the system.

Therefore, simply looking at the number of hours a generator operates each year does not give the complete picture.

Why Short, Light-Load Operation Can Be Challenging

Consider a standby generator that is started every week for only ten minutes without a significant electrical load. The engine starts, but the exhaust may remain relatively cool before the generator is switched off again.

Repeated short cycles can contribute to soot, moisture and unburned fuel accumulating in the exhaust system. They also provide limited opportunity for the exhaust-treatment system to reach its intended operating conditions.

By contrast, an emergency DG set that runs for several hours during an actual outage and carries a meaningful load has a very different operating profile.

load and run duration should be considered alongside annual operating hoursThis is why when assessing an RECD installation.

whether an RECD is suitable for a DG set that runs only occasionallyFor a deeper look at this issue, Aceget's guide on provides a detailed comparison of different occasional-use patterns.

Four Common Occasional-Use Scenarios

Occasionally operated generators generally fall into a few practical categories.

1. Standby generators: These remain idle most of the time but operate during grid failures. Their real outage runs may be relatively long, but regular testing between outages remains important.

2. Event-based generators: Generators used for weddings, festivals, film production or occasional events may operate intensively for a few days and then remain unused for weeks or months.

3. Seasonal generators: Some generators are primarily needed during particular seasons or periods of increased electricity demand.

4. Emergency-only generators: These may remain unused for extended periods and are expected to start immediately when an emergency occurs.

Each profile creates different requirements for inspection and exercising.

A Proper Exercise Routine Matters

For an occasionally used DG set, the testing routine should not simply involve starting the engine for a few minutes and shutting it down.

Where practical, operators should conduct periodic loaded exercises according to the generator manufacturer's recommendations. Cummins maintenance guidance, for example, recommends regular exercise of diesel generator sets and minimising no-load operation because unburned fuel can accumulate in the exhaust system.

A good operating log can record:

Date and duration of each run
Approximate load carried
Smoke or unusual exhaust observations
RECD alarms or indications
Back-pressure readings where applicable
Maintenance and inspection dates

This information becomes particularly useful when a generator has very low annual running hours because calendar-based inspection can become more important than simply counting operating hours.

Compliance Should Be Checked Separately From Usage

Another common misconception is that a DG set running only a few hours per year automatically falls outside applicable emission requirements.

cpcb.nic.inThat assumption should be avoided. India's regulatory framework contains specific requirements for generator-set emissions, and CPCB publishes technical and regulatory material covering generator sets and emission-control requirements.

The applicable requirement can depend on factors such as the generator's specifications, installation, location, regulatory framework and applicable state or local requirements. Therefore, owners should confirm their particular compliance position with the relevant pollution-control authority rather than relying solely on annual running hours.

Environment (Protection) Rules cpcb.nic.inThe also establish emission requirements for new generator-set engines, illustrating why generator compliance should be considered as part of the wider regulatory framework rather than simply as an operating-cost calculation.

What About the Cost of an RECD for a Rarely Used Generator?

Cost per operating hour can look high when a DG set runs very little.

For example, suppose an emission-control system and its associated installation and servicing costs are spread over many years while the generator operates only a few dozen hours annually. The resulting cost per running hour will naturally be higher than for a generator operating hundreds or thousands of hours.

However, compliance decisions should not be based only on cost per operating hour. The value of a standby generator is its availability when the main power supply is unavailable. If the generator is essential to a facility, the owner needs to consider compliance, reliability, maintenance and operational readiness together.

In some cases, organisations may instead evaluate whether maintaining an owned standby generator remains practical compared with other backup-power arrangements.

Questions to Ask Before Selecting an RECD

Owners of rarely used generators should discuss their actual operating pattern with the RECD supplier. Useful questions include:

Is the proposed device suitable for the generator's typical load profile?
What maintenance interval is recommended when annual running hours are very low?
What happens if the generator remains unused for several months?
How should the system be checked before a long emergency run?
How should back pressure or other operating parameters be monitored?
What documentation is supplied for inspection and compliance purposes?

The answers should be specific to the generator model and duty profile rather than based only on its rated capacity.

Conclusion

RECD for DG Set can be suitable for an occasionally operated generatorAn , but low annual usage does not automatically make the decision simple. The important factors include how long each run lasts, how much load the DG carries, how frequently it is exercised, and how well the system is inspected during long idle periods.

The best approach is to assess the generator's actual duty pattern, follow the manufacturer's maintenance recommendations, conduct meaningful periodic testing, and confirm the applicable regulatory requirements

RECD for DG Set Used Occasionally: Is It a Practical Choice?

RECD For DG Set