RECD for Construction Projects: Planning for Changing Power Demand

Most buildings have a power demand that changes slowly over years. A construction site changes its demand every few months. In the first weeks there is a site office and a few lights. Then dewatering pumps run day and night in the excavation. Then a batching plant starts, tower cranes go up, hoists climb the face of the building, welding sets multiply, and finally the MEP team switches on chillers and lifts for testing before the permanent supply arrives.

A diesel generator chosen for one phase is often the wrong size for the next. That matters for compliance and cost, and it matters especially when the set carries a retrofit emission control device, because the filter inside behaves well only when the engine works hard enough. This guide treats an RECD for construction projects as a lifecycle problem. It maps the power demand of a typical project phase by phase, sets out decision gates where the DG strategy should be reviewed, and covers the practical issues of cranes, mobility, contracts and pollution control stoppages.

Why Construction Sites Are Under Scrutiny

Construction is one of the most visible sources of urban air pollution. Dust from excavation, demolition and material handling is the obvious part, as discussed in our article on construction dust and city air pollution. Diesel exhaust from generators, pumps and machinery adds to it.

In the National Capital Region, two sets of rules matter most.

First, CAQM Direction No. 76 linked DG compliance to capacity: dual fuel for sets of 19 to 125 kW, dual fuel or an RECD for 125 to 800 kW, and an RECD for sets above 800 kW. Construction sites using DG sets are covered like any other user.

Second, the Graded Response Action Plan schedule sets out actions as air quality worsens. At higher stages, non-essential construction and demolition can be halted across NCR, with exemptions for certain categories of project. Stage III restrictions have been imposed and lifted several times in recent winters, for example in January 2026. Our GRAP stage explainer covers what changes at each level.

Always check the current direction, GRAP stage and SPCB requirements for your site. Rules have been revised often.

The Construction Load Curve

The table below shows an illustrative load curve for a 30-month residential tower project in Gurugram, before the permanent electricity connection is energised. Your project will differ, but the shape is typical.

Phase	Months	Main electrical loads	Average kW (illustrative)	Peak kW (illustrative)
Mobilisation	1 to 2	Site office, security lighting, labour camp, small tools	30	50
Excavation and dewatering	3 to 6	Submersible dewatering pumps running continuously, lighting, camp	110	150
Raft and basement	7 to 11	Batching plant, concrete pumps (if electric), bar bending and cutting, vibrators, dewatering	160	280
Superstructure	12 to 24	Two tower cranes, two hoists, batching plant, welding, camp	220	380
Finishing	25 to 28	Hoists, plastering and grinding tools, lighting, camp	140	220
MEP testing and commissioning	29 to 30	Chillers, pumps, lifts, fire systems under test	260	400

Three observations matter for DG strategy.

1. Peak demand is several times early-phase demand. A set sized for superstructure or MEP testing will be very lightly loaded during mobilisation and excavation.
2. Average is well below peak in every phase. Batching plants, cranes and hoists are intermittent, so peaks are short.
3. The permanent supply changes everything. Many projects obtain a temporary construction connection from the distribution company partway through, after which the DG becomes backup rather than prime power. When that happens, DG running hours fall sharply.

Our guide on load calculation basics before buying a generator shows how to build a load list. On a construction site, build one for each phase.

Why the Load Curve Matters to an RECD

The diesel particulate filter in an RECD traps soot and needs hot exhaust to burn it off during running. That requires the engine to work at a reasonable share of its rating. A generator running at 10 to 20% load produces cool exhaust; soot builds up faster than it burns, backpressure rises and the engine may also suffer wet stacking.

Construction sites are prone to exactly that problem, because a set sized for the peak phase spends months at light load in the early phases, during GRAP stoppages and after grid power arrives. Our explainers on generator load factor and duty cycle and on standby versus prime power generators give useful background.

Comparing two strategies on the same curve

Take the load curve above and compare two DG strategies.

Option A: one 625 kVA set (about 500 kW)

Phase	Average kW	Load on one 500 kW set
Mobilisation	30	6%
Excavation	110	22%
Raft and basement	160	32%
Superstructure	220	44%
Finishing	140	28%
MEP testing	260	52%

Option B: two 250 kVA sets (about 200 kW each), run one or both as needed

Phase	Sets running	Average kW	Load per running set
Mobilisation	One (or a small rental set)	30	15% on one set; better on a small set
Excavation	One	110	55%
Raft and basement	One, second on demand for peaks	160	80% on one, or 40% each when both run
Superstructure	Two	220	55% each
Finishing	One, second on demand	140	70% on one
MEP testing	Two	260	65% each

Option B keeps each running set in a far healthier load range for most of the project. It also provides redundancy: if one set fails, the other can keep dewatering pumps and essential loads running. The trade-off is a synchronising panel or a well-designed changeover arrangement, and two exhaust systems to manage. The general principles are in our generator sizing for factories guide, which applies equally to a construction site.

For mobilisation, a small rental set or early grid connection is often better than running a large set almost empty.

DG Decision Gates Through the Project

Rather than choosing a DG once and living with it for thirty months, review the strategy at four gates.

Gate 0: Before mobilisation

• Apply for a temporary construction power connection as early as possible. The sooner grid power arrives, the fewer DG hours you need.
• Decide whether DG sets will be owned by the developer, supplied by the EPC contractor or rented.
• Write the emission compliance requirement into contracts and rental agreements, so every set that arrives on site is compliant from day one.
• Choose sets to suit the first two phases, with a plan to add or swap capacity later.

Gate 1: Before superstructure

• Recalculate load with the actual tower crane and hoist specifications.
• Check that the DG arrangement can handle crane and hoist starting and braking (see the next section).
• Decide whether to add a second set or swap to a larger one.

Gate 2: At finishing

• Load usually falls. Consider releasing a rental set or running one set instead of two.
• If grid power has arrived, move the DG to backup duty and set up periodic loaded runs.

Gate 3: Before MEP testing

• Testing chillers, pumps and lifts on DG power can create the highest load of the project. Plan it with the MEP contractor.
• Confirm when permanent supply will be energised, so you do not over-invest in temporary capacity.

Tower Cranes, Hoists and Generators

Tower cranes and construction hoists are the most demanding electrical loads on most sites, and they behave differently from pumps or lights.

Starting current. Hoist motors draw high current when lifting from rest. The generator must supply it without excessive voltage dip, or the crane’s drive may trip.

Regenerative energy. When a crane lowers a heavy load, its drive can return energy to the supply. A utility grid absorbs this easily. A diesel generator cannot absorb much reverse power, and a sudden flow back can disturb its voltage and frequency or trip protection. Many crane drives use braking resistors to handle this, but you should confirm with the crane supplier that the crane is suitable for generator supply and what generator size and type they recommend.

Harmonics. Variable frequency drives on cranes and hoists draw non-linear current, which can affect alternator heating and voltage quality.

None of this is caused by the RECD. A correctly sized RECD keeps backpressure within the engine maker’s limit, so the engine’s ability to take load steps should not change in a meaningful way. Our post on whether an RECD changes a generator’s usable power output explains this. But crane behaviour does influence DG sizing, and DG sizing influences how well the filter regenerates.

Dewatering: The Steady Load That Helps

Dewatering pumps are often the friendliest load a construction DG ever sees. They run continuously, at fairly constant power, for weeks or months. A set carrying dewatering pumps at a sensible share of its rating will regenerate its filter well.

Two cautions:

• Do not oversize for dewatering. If the excavation only needs a few pumps, a large set will run light.
• Dewatering cannot stop. In many soils, stopping pumps can flood the excavation or destabilise the sides. Any DG downtime, including RECD fitment, must be planned with backup pumping power.

GRAP Stoppages: Planning for the Quiet Weeks

When higher GRAP stages halt non-essential construction, the site does not empty. Security, lighting, the labour camp, dewatering in some cases and site offices continue. The DG load drops to a small fraction of normal.

If your DG is fitted with an RECD, those quiet weeks are a light-load period. Plan for them:

• Switch to the smallest set that can carry the remaining loads, if you have more than one.
• Use grid supply for camp and lighting where available.
• Watch backpressure trends on the RECD’s IoT display during stoppages, and schedule a loaded run before full work resumes if the vendor recommends it.

Note that GRAP stages also restrict DG use in some categories. Check which uses are permitted for your site at each stage. Our post on GRAP rules for DG sets in Delhi NCR covers this.

Construction stoppages often fall in November to January. If you are planning an RECD fitment, doing it before October avoids the risk of being unable to run a non-compliant set during the winter season.

Dust and the Engine

A construction site is one of the dustiest places a generator can work. Cement, sand, soil and grinding dust load the air filter quickly. A restricted air filter makes the engine run rich, raises fuel use and increases soot output, which loads the RECD faster.

• Locate the DG away from excavation edges, batching plants, crushers and unpaved haul roads where possible.
• Check air filter restriction often, and keep spare elements on site. Our generator air filter maintenance guide explains how.
• Keep the radiator clean, especially in summer.
• Wet down nearby haul roads as part of the site’s dust control plan; it helps the DG as well as the neighbours.

Mobile Sets, Moving Work Fronts

On large sites, DG sets are often moved as work fronts shift: from one tower to another, from basement to podium, or from one phase of a township to the next. A set with an RECD can move too, but plan for it.

• Mounting. The RECD should be mounted on the DG’s own skid, canopy or a frame attached to it, so the set moves as one unit. A device fixed to a separate structure must be disconnected and reconnected every time.
• Transport. Secure the device for transport and check mountings and joints after each move.
• Recommissioning. After a move, run the set on load and check backpressure, temperatures and alarms before relying on it.
• Placement at the new location. Each new position needs its own check of outlet direction, proximity to labour camps and neighbours, and vehicle protection.

If a project ends and the set is sold or returned, the RECD may be moved to another generator. Our article on whether an RECD can be transferred to another diesel generator explains the conditions.

Owned, Contractor-Supplied or Rented Sets

Model	Typical situation	RECD considerations
Developer-owned	Large developers with many projects	RECD investment can be redeployed across projects; standardise sizes
EPC contractor-supplied	Turnkey and item-rate contracts	Make compliance a contract condition; ask for certificates before the set enters site
Rented	Short phases, peak top-up, small sites	Ask rental firms for sets already fitted with certified devices or dual fuel; check documents at the gate

Our guides on diesel generator rental cost in India and generator rental vs purchase help with the commercial decision, and can you install an RECD on a rented diesel generator covers rental arrangements.

A gate check for every DG

Security at the site gate checks vehicle documents. Add DG sets to that list. Before any set enters site, the site engineer should see:

• The set’s rating and nameplate
• Evidence of the emission route for that rating, such as RECD type approval and test certificate or dual fuel documentation
• Recent service record
• Consent or registration documents where your SPCB requires them

A set that arrives without documents is a liability, because the developer or contractor running the site will answer for it during an inspection. See what happens during a pollution control board inspection.

Fitting an RECD to a Set Already on Site

If you are retrofitting a set mid-project:

• Schedule fitment during a phase with lower demand or when grid power is available.
• Never leave dewatering pumps without power. Arrange a rental set for the day if needed.
• Coordinate crane use: the site’s own crane may help lift the device, but only under a proper lifting plan.
• Issue a hot work permit and keep combustibles such as shuttering ply, formwork oil and packaging well clear.
• Expect a day or two of downtime per set, after survey and fabrication. Our RECD installation timeline covers the stages.

Contract Clauses Worth Adding

Most emission problems on construction sites start in the contract, where the DG is a line item that nobody reads closely. A few clauses make a large difference.

• Compliance of every set. Every DG brought to site, by the contractor or any subcontractor, must comply with the emission route applicable to its rating, with documents produced before mobilisation.
• Right to refuse. The site in-charge may refuse entry to, or stop, any set without documents or with visible smoke.
• Sizing by phase. The contractor submits a power plan by phase and updates it at each decision gate, rather than mobilising one large set for the whole project.
• Monitoring access. Where sets carry IoT monitoring, the developer’s project team gets read access to the data.
• Maintenance responsibility. The party supplying the set maintains both engine and emission device, including filter-related service, and keeps logs on site.
• Removal at handover. Temporary sets and their exhaust supports are removed, and any damage made good, when permanent power is commissioned.

Clauses like these move the compliance burden to the party that controls the equipment, and they give the developer evidence if an inspector asks.

Fuel Handling on a Busy Site

Diesel on construction sites arrives in small tankers or barrels, is stored in temporary tanks and is shared between generators, pumps and machinery. Quality varies, and contamination with water or dirt is common. Poor fuel raises soot output and can harm both the engine and the after-treatment device.

Keep a dedicated, covered tank for generator fuel, filter fuel as it is transferred, and buy from a known supplier. Record deliveries against run hours; a mismatch can point to theft or leaks. Our article on how ultra-low sulphur diesel improves emission control explains why fuel quality matters for any after-treatment system.

Neighbours and Labour Camps

Construction sites sit next to existing homes, schools and offices, and often house workers in camps on site. The DG outlet should point away from both. An RECD sharply reduces soot, which neighbours notice, but the plume still follows the outlet and the wind. Check the outlet each time a set is placed, and keep it away from camp kitchens and sleeping areas.

The Head Office View Across Several Sites

Developers and large contractors rarely run one site at a time. A head office with eight or ten live projects can treat its DG sets as a pool rather than as site property.

Keep a simple register showing each set’s rating, location, current project phase, emission route and document status. Review it monthly alongside the project programme. When one site moves into finishing and its load falls, a set can be released to another site entering superstructure, instead of renting fresh capacity there while the first set idles. Sets fitted with RECDs and IoT monitoring make this easier, because the head office can see run hours and load on each set without waiting for site reports.

Standardising on two or three set sizes across projects also simplifies spares, training and paperwork, and makes it easier to move an emission control device from one set to another of the same rating when needed.

Frequently Asked Questions

Who answers to the inspector: the developer or the contractor?

Both may be asked. The developer usually holds the project approvals, while the contractor operates the equipment. Clear contract clauses on DG compliance, and documents kept on site, protect both parties.

Is an RECD practical for a construction site whose load keeps changing?

Yes, if the DG strategy follows the load. Use more than one smaller set, or swap sets between phases, so that running sets stay reasonably loaded. A single large set sized for the peak will run light for months, which is hard on the filter.

Do construction DG sets in NCR need emission control?

DG sets on construction sites are covered by the same CAQM framework as other users, with the route depending on capacity. Check the current direction and your SPCB for your sets.

Can tower cranes run on a DG with an RECD?

Yes, if the DG is suitable for crane loads. Check starting current, regenerative energy and harmonics with the crane supplier. The RECD itself does not change the engine’s load acceptance when correctly sized.

What happens to the RECD during GRAP construction stoppages?

The DG usually runs very light, carrying only camp, lighting and security. Use the smallest suitable set or grid power, and plan a loaded run before work resumes if the vendor recommends it.

Can we move the RECD with the DG around site?

Yes, if it is mounted on the DG’s skid or canopy. Check mountings after each move and recommission on load before relying on the set.

Should we rent compliant sets or fit RECDs to our own?

For short phases and peak top-ups, renting compliant sets is often simpler. For developers with a steady pipeline of projects, owning sets with RECDs and redeploying them can make sense.

Plan Power the Way You Plan the Programme

A construction programme has phases, milestones and reviews. Give the DG strategy the same treatment: a load curve, decision gates and a check at the site gate for every set. Aceget supplies CPCB type-approved RECDs for DG sets from 25 kVA to 2500 kVA, with IoT monitoring that lets site and head office teams see how each set is running. To discuss a project, contact Aceget or explore the retrofit emission control device range.