Most DG installation problems are decided before the genset arrives. The set itself is a known quantity — what varies wildly is the site: rooms that starve the radiator, foundations poured to the wrong level, exhaust runs that choke the engine, day tanks plumbed below the fuel pump. This checklist is our synthesis of Cummins’ installation recommendations (Bulletin 3243795, Rev 06) — the same document our engineers work to on turnkey jobs — organised as what to verify before delivery day.
TL;DR — the numbers that catch people out
- Clearances: 1.5 m at the sides, 3 m in front of the radiator discharge, 2 m behind the alternator
- Room air openings: fresh-air inlet ≥ 1.5× radiator area, hot-air outlet ≥ 2.5× radiator area
- Room temperature rise: 10 °C max over ambient (less in very hot regions)
- Foundation: 150 mm proud of ground, 150 mm larger than the enclosure all round, level within ±5 mm
- Day tank (750 kVA and up): 990 L, fuel level never below 150 mm above the engine fuel inlet
- Earthing: four pits — two body, two neutral — at ≤ 1 Ω (IS 3043)
- Exhaust: insulate indoor runs (50 mm rock wool + aluminium cladding), bellow every 6–10 m, condensate drain after the silencer
Location: where the set sits decides how it breathes
Point the radiator discharge away from the prevailing wind — wind blowing into the hot-air outlet recirculates heat back through the set. Where the site gives you no choice, a wind barrier does the job. Keep the set away from dust-heavy or corrosive air (cement, stone crushing, acid fumes) or specify suction filters and sand louvres for the canopy. On the coast or anywhere humid, alternator space heaters are not optional — condensation inside a stopped alternator is how winding failures start.
Between two sets, keep at least 1.5 m. And leave yourself a way in: the room opening has to admit the genset, not just the people.
Ventilation: the most under-designed system on Indian sites
A genset room has one thermal job: carry away engine, alternator and exhaust-pipe heat while feeding the engine clean combustion air. Cummins’ rule of thumb for open sets in rooms is a fresh-air inlet of at least 1.5 times the radiator core area and a hot-air outlet of at least 2.5 times — and airflow should travel alternator-end to engine-end.
The acceptance test is simple and worth writing into any installation contract: run the set at load for an hour, then compare room temperature (measured at the engine’s air-cleaner inlet) with outside ambient. More than a 10 °C rise means the ventilation failed, whatever the drawings say. Above 40 °C ambient the allowance tightens further.
Skip this and you get the classic symptoms: derated output on hot afternoons, high exhaust temperatures, nuisance shutdowns, and a room no operator wants to enter.
Foundation: concrete is cheap, re-pouring it is not
- Design against the dynamic load, not just the static weight — for small sets the running load is taken as roughly 2.5× static. And the static weight is more than people guess: a 1010 kVA set in its acoustic enclosure is about 14.7 tonnes on the OEM’s own weight table before any dynamic factor.
- Make the block at least 150 mm larger than the enclosure on every side, and raise it 150 mm above finished ground so rain splash and washdown water stay out of the base rails.
- Level matters more than mass: within ±5 mm across the mounting area for large sets (tighter, ±2.5 mm, below 750 kVA), with steel shims — never packers of whatever is lying around — so every anti-vibration mount carries its share. Unevenly loaded AVMs transmit the vibration they were bought to absorb.
- Where the building is vibration-sensitive, cast the DG foundation isolated from the building raft, and let a structural engineer confirm soil bearing and any seismic requirement.
For rooftop installations the rules tighten again: mount over columns and beams (never mid-slab), have the slab checked for static plus dynamic load, hold the pad level within ±3 mm, and put a resilient layer under the enclosure frame. We covered stack height for tall buildings in the stack-height guide — rooftop sets usually trigger it.
Exhaust: back pressure is a silent power thief
Every bend, metre of pipe and undersized duct raises exhaust back pressure — and past the engine’s limit that means lost fuel economy, high exhaust temperatures and shortened engine life. Design habits that keep you inside the limit:
- Size for a gas velocity around 35–40 m/s and leave a 20% margin to the engine’s back-pressure ceiling in a new installation. A single 90° elbow costs the same as 5–8 m of straight pipe, so route with the fewest, softest bends you can.
- Insulate indoor runs — 50 mm rock wool under aluminium cladding — or the exhaust becomes a radiator inside the room (roughly a kilowatt per metre even after insulation).
- Give thermal expansion somewhere to go: a bellow at the engine (with a rigid anchor immediately above it, so pipework forces never reach the turbocharger), another after the silencer, and one every 6–10 m of horizontal run.
- Slope horizontal runs away from the engine, fit a rain cap and bird mesh at the outlet, and put a condensate drain after the silencer — rainwater and condensate must never have a path into a stopped engine.
- Twin-bank engines get twin exhausts. From about 1000 kVA the engine is a V configuration with two turbochargers: two exhaust lines leave the set, each with its own silencer, and a fabricated Y-joint after the silencers merges them into one common pipe — sized to the rating, 14 inch at 1000 kVA up to 18 inch at 2000 kVA, MS B-class ERW, insulated and aluminium-clad like the rest of the run.
- One set, one stack. A single set’s two banks meeting in a Y is standard; manifolding separate gensets into a common exhaust is not — it invites condensate and exhaust gas into whichever engine is idle. Where a site regulation forces a shared chimney, it needs per-set drains and carefully angled entries — engineered, not improvised.
Stack height is a separate, statutory question — the CPCB formula and the >800 kW regime — and the structure to get there is its own discipline: exhaust stack structures.
Fuel: gravity does half the engineering
Up to about 700 kVA the tank is built into the skid and this section is free. From 750 kVA up, a separate 990-litre day tank arrives loose, and its position is the whole game: mounted so the minimum fuel level stays at least 150 mm above the engine fuel inlet (positive suction head), but not so high that static head pressurises the return line.
Tank and pipe practice, condensed: mild steel tank (never galvanised inside — zinc and diesel react), a drain at the low point for water, a breather, filler screens, suction and return kept 300 mm apart, and carbon-steel seamless piping with the engine’s flexible hoses making the final connection. No GI, no copper, no thread tape. Bulk storage beyond the day tank brings the Chief Controller of Explosives rules into play — a licensing question as much as a piping one.
Earthing: four pits, one ohm
IS 3043 practice, and rule one on every commissioning snag list: two earth pits for the body, two for the neutral, each connection able to carry fault current, and measured resistance no more than 1 Ω. The subtlety that catches contractors: on sets where the engine-alternator block sits on AVMs above the base rail, the earth bond must land on the engine/alternator, not the rail — rubber mounts make the rail an island.
Noise and vibration: the numbers inspectors use
The noise norm is 75 dB(A) at 1 m for sets up to 1000 kVA manufactured on or after 1 January 2005 (outside that coverage, a 25 dB(A) insertion-loss requirement takes over) — the subject of our noise-norms guide. Vibration is measured to ISO 8528-9; what installation controls is transmission — even loading on the AVMs and, where needed, an isolated foundation.
What this list is for
Every item above is checkable before the truck arrives — and that is exactly how we run turnkey installations: the civil, exhaust, fuel and earthing scope engineered against the same bulletin the genset OEM will audit against at commissioning. If you would rather hand over the whole list than police it, that is the service.
Sources: Cummins “DG Set Installation Recommendations”, Bulletin 3243795 Rev 06; IS 3043 (earthing); ISO 8528-9/-10 (vibration and noise measurement); CPCB norms as cited in the linked guides. This checklist summarises installation practice — your genset model’s own installation drawings and O&M manual govern where they differ.